Mastitis

What is Mastitis

Mastitis is inflammation of the breast tissue. It occurs most often in women who are breastfeeding, but it can also affect other women, and sometimes even men.

9 Interesting Facts of Mastitis

1. Mastitis is inflammation of the breast; it may be infectious or noninfectious in origin
2. Most common form of mastitis is lactational, but mastitis also occurs in women who are not lactating and in neonates with breast hypertrophy caused by exposure to maternal estrogen
3. Women with mastitis typically present with sudden onset of fever and flulike symptoms as well as unilateral, localized breast tenderness, erythema, warmth, and induration
4. Initial diagnosis of mastitis is clinical, based on history and physical examination
5. The most common bacteria causing infectious mastitis is Staphylococcus aureus, often MRSA
6. Treatment of mastitis most commonly includes antibiotic drug therapy, although evidence supporting or refuting its effectiveness is lacking for treatment of routine lactational mastitis
7. Patients not responding promptly to treatment need to undergo further diagnostic testing including cultures and ultrasonography to rule out abscess
   • In postmenopausal women and women who are not responding as expected to treatment, suspicion for breast malignancy is elevated
8. Breast abscess is the most common complication of mastitis
9. Continued breastfeeding does not pose a risk to the infant and is encouraged to resolve milk stasis and ensure adequate drainage

What are the causes?

This condition is usually caused by a bacterial infection. Bacteria enter the breast tissue through cuts or openings in the skin. Typically, this occurs with breastfeeding because of cracked or irritated nipples. Sometimes, it can occur when there is no opening in the skin. This is usually caused by plugged milk ducts.

Other causes include:

• Nipple piercing.
• Some forms of breast cancer.

What are the symptoms?

Symptoms of this condition include:

• Swelling, redness, tenderness, and pain in an area of the breast. The area may also feel warm to the touch. These symptoms usually affect the upper part of the breast, toward the armpit region.
• Swelling of the glands under the arm on the same side.
• Fever.
• Rapid pulse.
• Fatigue, headache, and flu-like muscle aches.

If an infection is allowed to progress, a collection of pus (abscess) may develop.

• Mastitis is inflammation of the breast; it may be infectious or noninfectious in origin 
  • Mastitis presents as acute onset of fever, chills, and extreme breast tenderness over an area of induration and firmness, usually on 1 breast 
  • Most common benign breast problem during pregnancy and the first 6 weeks postpartum. Also can be unrelated to pregnancy 
  • Incidence of lactational mastitis is usually reported to be about 10%, but symptoms may occur in as many as 33% of breastfeeding mothers 

Classification

• Lactational 
  • Infectious
  • Noninfectious
• Nonlactational 
  • Infectious
  • Granulomatous
  • Plasma cell
  • Lymphocytic
  • Foreign body reaction

History

• Acute onset 
  • Symptoms
    • Severe mastalgia (breast pain), usually unilateral
    • Fever, chills, fatigue, and malaise mimicking flu symptoms
    • Vomiting and headache may occur
  • Timing in breastfeeding women
    • Most commonly occurs during second or third postpartum week, with most incidences occurring in the first 12 weeks after delivery 
      • Milk supply on affected side may temporarily decrease

Physical examination

• Fever, usually higher than 38.3°C 
• Unilateral; breast shows wedge-shaped area of: 
  • Erythema
  • Induration and firmness
  • Extreme tenderness
  • Warmth
• Axillary lymphadenopathy on affected side 
• Breast abscess
  • Well-circumscribed fluctuant mass in affected breast 

Causes and Risk Factors

Causes

• Lactational
  • Infectious
    • Believed to arise from entry of bacteria or fungus through the nipple into the duct system
      • Bacteria
        • Staphylococcus aureus (most common, often MRSA) 
        • Coagulase-negative staphylococci also common
        • Other aerobic bacteria, often in polymicrobial infection 
          • Streptococcus
          • Enterobacteriaceae
          • Corynebacterium
          • Escherichia coli
          • Pseudomonas
        • Anaerobic bacteria may exist in polymicrobial infection 
          • Peptostreptococcus
          • Eubacterium
          • Clostridium
          • Fusobacterium
          • Veillonella
        • Unusual bacteria 
          • Bartonella henselae
          • Mycobacterium species (tuberculosis and atypical forms)
          • Actinomyces
          • Brucella
          • Typhus (in endemic areas)
      • Fungi 
        • Candida (common)
        • Cryptococcus (uncommon)
      • Other unusual pathogens 
        • Parasites
  • Noninfectious
    • Milk stasis
      • Ineffective or obstructed milk removal resulting in leakage of inflammatory cytokines 
      • Clinically mimics an infectious process
• Nonlactational
  • Infectious
    • Often associated with a cyst or rupture of a cyst in the breast 
      • Bacteria
        • Staphylococcus aureus (most common)
        • Syphilis
        • Tuberculosis
        • Other atypical bacteria similar to those present in lactational mastitis
      • Fungus
      • Other unusual pathogens 
    • Periductal mastitis or duct ectasia 
      • Chronic relapsing infection
      • Associated with smoking and diabetes
      • Often polymicrobial, both aerobes and anaerobes
      • Frequently features a mammary fistula running between periareolar skin and the ductal mammary system
  • Granulomatous mastitis
    • Idiopathic granulomatous lobular mastitis
      • Rare disease with unknown cause 
      • Granulomas containing neutrophils found within the lobules are sterile on biopsy 
      • May affect any age group, but most often diagnosed in young to middle-aged women 
      • Sometimes associated with women who have given birth or who take oral contraceptives 
      • May mimic inflammatory breast cancer 
    • Cystic neutrophilic granulomatous mastitis 
      • Granulomas containing neutrophils are found within the lobules, similar to idiopathic granulomatous lobular mastitis
      • Unlike idiopathic granulomatous lobular mastitis, granulomas contain cystic spaces consistent with dissolved lipid
      • Seen in women who have given birth, are lactating, and are nulliparous but have hyperprolactinemia
      • Corynebacterium is found in the lipophilic areas (most common is Corynebacterium kroppenstedtii, which is lipophilic)
      • Hypothesized that women unable to breastfeed from 1 breast develop stasis of lipid-rich milk secretions in that breast, which predisposes them to cystic neutrophilic granulomatous mastitis
      • Cystic neutrophilic granulomatous mastitis is relatively newly recognized; it is possible that some or all cases of idiopathic granulomatous lobular mastitis are actually cystic neutrophilic granulomatous mastitis and related to Corynebacterium
  • Plasma cell
    • Periductal inflammation 
    • Plasma cell reaction to retained ductal secretions 
    • May be clinically and radiologically indistinguishable from inflammatory breast cancer 
    • Some evidence of autoimmune cause 
    • Often associated with nipple retraction 
    • Rare form of mastitis
  • Lymphocytic (also called sclerosing lymphocytic lobulitis)
    • Aggregates of lymphocytes within and surrounding terminal ducts and lobules with surrounding stromal fibrosis 
    • May represent an immunologic reaction to extruded breast milk or to breast tissue itself but is currently deemed idiopathic 
    • Has been associated with underlying autoimmune disease
    • Rare form of mastitis
  • Foreign body reaction
    • Nipple rings 
      • Nipple piercings are associated with mastitis, especially in people who smoke
    • Silicone
      • Leaked from breast implant 
      • Injected for cosmetic reasons 

Risk factors and/or associations

Age

• Most often occurs in reproductive age women
• May occur in neonates; related to breast tissue hypertrophy caused by exposure to maternal estrogen
  • In first 2 weeks of life, incidence is equal in boys and girls 
  • After age 2 weeks, twice as common in girls 
• Rare in postmenopausal women
  • Maintain high suspicion for inflammatory breast cancer in any postmenopausal woman with symptoms suggesting mastitis

Sex

• Primarily occurs in women

Genetics

• No genetic patterns identified

Ethnicity/race

• No ethnic or racial differences are currently identified, but in rare cases, differences may be associated with underlying disease (eg, autoimmune diseases, tuberculosis)

Other risk factors/associations

• Lactation and breastfeeding
  • Previous mastitis
  • Milk stasis caused by missed feedings or infant latching difficulties
  • Cleft palate or other oral malformations in infant
  • Use of manual breast pump
• Breast cysts, especially with rupture
• Smoking
• Diabetes
• HIV infection
  • Unusual pathogens may be found in patients who have underlying HIV disease; these pathogens may be the first presentation of HIV infection

How is this diagnosed?

This condition can usually be diagnosed based on a physical exam and your symptoms. You may also have other tests, such as:

• Blood tests to determine if your body is fighting a bacterial infection.
• Mammogram or ultrasound tests to rule out other problems or diseases.
• Testing of pus and other fluids. Pus from the breast may be collected and examined in the lab. If an abscess has developed, the fluid in the abscess can be removed with a needle. This test can be used to confirm the diagnosis and identify the bacteria present.
• If you are breastfeeding, breast milk may be cultured and tested for bacteria.

• Diagnosis of mastitis usually is based solely on clinical presentation, as determined by patient history and physical examination
• Laboratory studies are not mandatory, but under selected circumstances, evaluation may include: 
  • Pregnancy test if pregnancy status is unknown or mastitis is unexpected (eg, in adolescent)
  • Microbiology studies
    • Bacterial counts, culture and sensitivities, Gram stain, and fungal and mycobacterial studies, which are generally reserved for: 
      • Hospital-acquired infection
      • Severe or unusual cases
      • Failure to respond to antibiotics within 2 days
      • Recurrent mastitis
    • Specimen sources for microbiologic studies can include:
      • Milk or nipple discharge, if present
      • Aspiration of abscess fluid, if abscess is present
      • Tissue biopsy, if biopsy is performed
  • Cytology
    • May use cytology to look for evidence of unusual pathogens as well as evidence of malignancy
    • Specimen sources for cytology can include:
      • Milk or nipple discharge, if present
      • Abscess fluid aspirate, if abscess is present and fluid is obtained
      • Biopsy tissue, if biopsy is performed
    • Useful in atypical cases, such as in nonlactating women with no signs of trauma and no focal area of infection of the breast
  • Blood testing
    • CBC with differential 
      • When systemic infection or abscess is suspected
      • In cases of treatment failure or recurrence
    • Blood cultures 
      • In neonates before beginning antibiotics
      • In patients in whom systemic infection or sepsis is suspected
  • Tuberculosis testing
    • When tuberculosis is suspected
      • PPD test
      • Interferon-γ release assays
  • Oral and nasopharyngeal cultures
    • In recurrent lactational mastitis to determine Staphylococcal carrier status
• Imaging studies are not standard for diagnosis; instead, ultrasonography is used to identify abscesses and investigate possible breast malignancy. 
• Biopsy is not standard for diagnosis but may be warranted for atypical presentation, uncertain diagnosis, and recurrence or treatment failure
  • If biopsy is done, send tissue sample for cytology to assess for malignancy and infection
  • Atypical cases include any nonlactating woman who has no signs of trauma (eg, abrasion, papule) and no focal infection of the breast

• β-hCG
  • Obtain in reproductive age women if pregnancy status is unknown
• HIV test
  • Consider if unusual pathogens are identified on milk or abscess fluid cultures
  • Unusual breast infection may be initial presentation of HIV
  • First step in testing is a fourth-generation assay that detects both HIV-1 and HIV-2 antibodies as well as HIV p24 antigen; a positive test result is usually reported as reactive 
  • Second stage of testing is the HIV-1/HIV-2 antibody differentiation immunoassay 
• Blood cultures
  • For systemic infection
  • In neonates before starting antibiotics
• CBC with differential
  • For systemic infection or abscess
  • In cases of treatment failure or recurrence
• Tuberculosis testing
  • Interferon-γ release assays (first choice when tuberculosis is suspected)
  • PPD test when tuberculosis is suspected, if interferon-γ release assay is not done
• Specimen cultures and antibiotic sensitivities
  • Milk or nipple discharge, when present (obtain by expressing from nipple; midstream milk specimen is preferred) 
    • Culture of breast milk may reveal infectious pathogen; antibiotic sensitivities aid in treatment tailoring
    • As collecting milk or nipple discharge is not a sterile process, use caution when interpreting results of bacterial counts
      • Bacterial counts lower than 10³ CFU/mL may indicate contamination rather than infection 
      • Bacterial counts greater than 10³ CFU/mL usually indicate active infection (true mastitis) 
  • Abscess fluid, if aspiration performed
    • Cultures and antibiotic sensitivities
  • Oral and nasopharyngeal cultures
    • Obtain in cases of recurrent lactational mastitis to determine staphylococcal carrier status
• Cytology
  • For atypical cases with concern for breast malignancy or unusual infection, consult an expert pathologist to microscopically review milk, nipple discharge, or abscess fluid
  • Atypical cases include any nonlactating woman who has no signs of trauma (eg, abrasion, papule) and no focal infection of the breast

• Ultrasonography
  • Indicated when abscess is suspected
  • Indicated in atypical cases, such as those with inconsistent signs or symptoms (eg, bilateral disease, slow or progressive onset)
    • Other atypical cases include any nonlactating woman who has no signs of trauma (eg, abrasion, papule) and no focal infection of the breast
  • Indicated in refractory cases of mastitis (if symptoms do not resolve within 7-10 days on antibiotics) 
  • Not indicated for routine mastitis
• Mammography
  • Limited value in assessing acute episodes of mastitis, but should be done after acute phase of routine mastitis if there is suspicion of malignancy
  • After acute phase of mastitis resolves, perform on women: 
    • Older than 40 years with mastitis
    • With findings that are complicated, atypical, or suspicious for malignancy
      • Atypical cases include any nonlactating woman who has no signs of trauma (eg, abrasion, papule) and no focal infection of the breast

Procedures

Breast biopsy

General explanation

• Percutaneous procedure to obtain breast tissue from an area of the breast found to be abnormal during physical examination or during imaging for histologic examination
• Most frequently done by percutaneous core needle biopsy 
  • Ultrasonographic guidance may be used for any lesion visible on ultrasonography
  • Stereotactic guidance may be used for any lesion visible on mammogram but not ultrasonogram
• In cases in which the lesion cannot be visualized or requires surgical resection, open surgical biopsy is performed

Indication 

• Breast inflammation that is atypical or has features suspicious for malignancy
  • Atypical cases include any nonlactating woman who has no signs of trauma (eg, abrasion, papule) or focal infection of the breast
• Breast inflammation that is recurrent or refractory to treatment

Contraindications

• Severe coagulopathy

Complications

• Infection (less than 0.1% incidence with percutaneous technique) 
• Hematoma or other bleeding (less than 0.1% incidence with percutaneous technique) 
• Poor wound healing or scarring in open biopsy
• Reaction to local anesthetics
• Reactions to general anesthesia, when used
• Pneumothorax (very rare) 

Interpretation of results

• Tissue obtained is sent for:
  • Gram stain
    • Bacteria, yeast, or parasites may be visualized microscopically
  • Culture and sensitivities
    • Organisms may be retrieved on culture media
    • Sensitivity is used to guide antimicrobial therapy
  • Histopathology and cytology
    • Histologic and cytologic examination can differentiate infectious from granulomatous, plasma cell, and lymphocytic mastitis, and can identify malignancy
      • In plasma cell mastitis, microscopic sections of lesions demonstrate ductal epithelial hyperplasia accompanied by an associated intense lymphoplasmacytic infiltrate 
      • In lymphocytic mastitis, circumscribed aggregates of lymphocytes within and surrounding terminal ducts and lobules are associated with surrounding stromal fibrosis 
      • In granulomatous mastitis, multiple necrotizing granulomata are found located in association with segmental and subsegmental lactiferous ducts in a lobulocentric pattern 

Aspiration of breast abscess

General explanation

• A needle, usually under ultrasonographic guidance, is used to withdraw fluid or pus from the abscess
  • Multiple aspirations may be required before abscess resolves 

Indication

• Mastitis with breast abscess seen on ultrasonogram

Contraindications

• Severe coagulopathy
• Surgical incision and drainage is recommended in a small percentage of cases when: 
  • Abscess is larger than 5 cm
  • Abscess is identified as multiloculated on ultrasonogram
  • Abscess has been present for an extended period

Complications

• Hematoma or other bleeding
• Infection
• Pain
• Reaction to local anesthetic

Interpretation of results

• Fluid tests
  • Gram stain
    • May identify organisms under microscopy
  • Culture and sensitivities
    • Organisms can be recovered on culture media
    • Sensitivity is used to guide antimicrobial therapy for both abscess and initial mastitis
  • Cytology
    • Malignant cells may be seen during cytologic evaluation of fluid

How is this treated?

Treatment for this condition may include:

• Applying heat or cold compresses to the affected area.
• Medicine for pain.
• Antibiotic medicine to treat a bacterial infection. This is usually taken by mouth.
• Self-care such as rest and increased fluid intake.
• If an abscess has developed, it may be treated by removing fluid with a needle.

Mastitis that occurs with breastfeeding will sometimes go away on its own, so your health care provider may choose to wait 24 hours after first seeing you to decide whether a prescription medicine is needed. You may be told of different ways to help manage breastfeeding, such as continuing to breastfeed or pump in order to ensure adequate milk flow.

Follow these instructions at home:

Medicines

• Take over-the-counter and prescription medicines only as told by your health care provider.
• If you were prescribed an antibiotic medicine, take it as told by your health care provider. Do not stop taking the antibiotic even if you start to feel better.

General instructions

• Do not wear a tight or underwire bra. Wear a soft, supportive bra.
• Increase your fluid intake, especially if you have a fever.
• Get plenty of rest.

If you are breastfeeding:

• Continue to empty your breasts as often as possible either by breastfeeding or by using a breast pump. This will decrease the pressure and the pain that comes with it. Ask your health care provider if changes need to be made to your breastfeeding or pumping routine.
• Keep your nipples clean and dry.
• During breastfeeding, empty the first breast completely before going to the other breast. If your baby is not emptying your breasts completely, use a breast pump to empty your breasts.
• Use breast massage during feeding or pumping sessions.
• If directed, apply moist heat to the affected area of your breast right before breastfeeding or pumping. Use the heat source that your health care provider recommends.
• If directed, put ice on the affected area of your breast right after breastfeeding or pumping:
  • Put ice in a plastic bag.
  • Place a towel between your skin and the bag.
  • Leave the ice on for 20 minutes.
• If you go back to work, pump your breasts while at work to stay within your nursing schedule.
• Avoid allowing your breasts to become overly filled with milk (engorged).

Contact a health care provider if:

• You have pus-like discharge from the breast.
• You have a fever.
• Your symptoms do not improve within 2 days of starting treatment.

Get help right away if:

• Your pain and swelling are getting worse.
• You have pain that is not controlled with medicine.
• You have a red line extending from the breast toward your armpit.

Differential Diagnosis

Most Common

• Breast engorgement
• Breast abscess
• Inflammatory breast carcinoma
• Mastitis as a symptom of other underlying disease

Treatment

Goals

• Relieve symptoms caused by inflammation and/or cure infection
• Preserve breastfeeding in lactating women
  • Most common reason cited by women who stop breastfeeding before the recommended 6 months of exclusive breastfeeding is complications, including mastitis 
  • Continuing breastfeeding is essential to maintain infant and maternal well-being
• Prevent development of duct blockage, abscess, and fistula

Disposition

Admission criteria

General admission criteria

• Signs of sepsis
  • Tachycardia
  • Hypotension
  • Persistent fever or chills
• Rapid progression of infection
• Immunocompromised states with mastitis

Criteria for ICU admission

• Severe sepsis with decompensation
  • Hemodynamic instability
  • Multi-organ failure

Recommendations for specialist referral

• Refer to general surgeon or breast surgeon if breast abscess is suspected
• Refer to primary care physician or breast specialist for follow-up if underlying mass or breast cancer is suspected

Treatment Options

Lactational and nonlactational mastitis are treated similarly, except that antibiotic therapy is always used in patients with nonlactational mastitis, whereas antibiotic therapy is variably used in patients who are lactating

Lactational mastitis

• Cornerstone of treatment is effective milk drainage (continued regular breastfeeding or pumping) with or without antibiotics, along with warm compresses and good self-care 
  • Duration of antimicrobial therapy is not well-established; 10 to 14 days is generally recommended, but 5 to 7 days may be adequate for patients with good clinical response 
  • In the United States, antimicrobial therapy to cover Staphylococcus aureus is routine; in non-US countries, milk drainage without antibiotics may be tried in mild cases initially

Nonlactational mastitis

• Initial treatment is antibiotic therapy to cover Staphylococcus aureus, warm compresses, and good self-care
• In adolescents or adults with sepsis or severe infection, initial treatment is hospitalization with IV antibiotics
• In all neonates with mastitis, initial treatment is hospitalization with IV antibiotics (oral antibiotics are not adequate owing to risk of neonatal sepsis)
  • Obtain blood culture for all neonates before beginning antibiotics
• In patients who do not respond promptly to antibiotic therapy, perform further diagnostic studies to rule out abscess and to determine underlying cause of mastitis
  • Culture and identify the infectious pathogen from breast milk, if present, and treat patient with appropriate antimicrobial therapy according to culture and sensitivity results
  • If underlying cause is noninfectious, treatment may include: 
    • Observation
    • Immunosuppressive agents
    • Surgical resection of affected areas

Supportive care measures (all patients)

• Analgesics, warm compresses, smoking cessation, proper nutrition, and—if lactating—effective milk removal from affected breast 

Additional therapy if an abscess is present

• Consult general surgeon for percutaneous drainage or incision and drainage
• Consider tailoring and continuing antibiotic therapy once culture and sensitivity results are available
  • Antibiotics are routinely continued after incision and drainage for an abscess caused by mastitis; however, evidence demonstrating that this use of antibiotics confers additional benefits beyond the procedure is limited 

Drug therapy

• Common empiric antibiotics for mastitis presumed to be infectious include: 
  • Methicillin-sensitive agents (if patient has no history of MRSA and there is low suspicion)
    • Outpatient
      • Cephalexin
        • Cephalexin Monohydrate Oral capsule; Adults: 250 to 500 mg PO every 6 hours for 10 to 14 days.
      • Dicloxacillin
        • Dicloxacillin Sodium Oral capsule; Adults: 125 to 500 mg PO every 6 hours for 10 to 14 days.
    • Inpatient
      • Nafcillin
        • Nafcillin Sodium Solution for injection; Neonates 34 weeks gestation and younger and 0 to 7 days: 25 mg/kg/dose IV every 12 hours.
        • Nafcillin Sodium Solution for injection; Neonates 34 weeks gestation and younger and older than 7 days: 25 mg/kg/dose IV every 8 hours.
        • Nafcillin Sodium Solution for injection; Neonates older than 34 weeks gestation and 0 to 7 days: 25 mg/kg/dose IV every 8 hours.
        • Nafcillin Sodium Solution for injection; Neonates older than 34 weeks gestation and older than 7 days: 25 mg/kg/dose IV every 6 hours.
        • Nafcillin Sodium Solution for injection; Infants 1 to 2 months: 100 to 200 mg/kg/day IV divided every 4 to 6 hours.
        • Nafcillin Sodium Solution for injection; Adults: 1 to 2 g IV every 4 hours for 10 to 14 days.
      • Oxacillin
        • Oxacillin Sodium Solution for injection; Neonates 34 weeks gestation and younger and 0 to 7 days: 25 mg/kg/dose IV every 12 hours.
        • Oxacillin Sodium Solution for injection; Neonates 34 weeks gestation and younger and older than 7 days: 25 mg/kg/dose IV every 8 hours.
        • Oxacillin Sodium Solution for injection; Neonates older than 34 weeks gestation and 0 to 7 days: 25 mg/kg/dose IV every 8 hours.
        • Oxacillin Sodium Solution for injection; Neonates older than 34 weeks gestation and older than 7 days: 25 mg/kg/dose IV every 6 hours.
        • Oxacillin Sodium Solution for injection; Infants 1 to 2 months: 100 to 200 mg/kg/day IV divided every 4 to 6 hours.
        • Oxacillin Sodium Solution for injection; Adults: 1 to 2 g IV every 4 hours for 10 to 14 days.
      • Cefazolin
        • Cefazolin Sodium Solution for injection; Neonates younger than 32 weeks gestation and 0 to 13 days†: 50 mg/kg/dose IV every 12 hours.
        • Cefazolin Sodium Solution for injection; Neonates younger than 32 weeks gestation and 14 days and older†: 50 mg/kg/dose IV every 8 hours.
        • Cefazolin Sodium Solution for injection; Neonates 32 weeks gestation and older and 0 to 7 days†: 50 mg/kg/dose IV every 12 hours.
        • Cefazolin Sodium Solution for injection; Neonates 32 weeks gestation and older and 8 days and older†: 50 mg/kg/dose IV every 8 hours.
        • Cefazolin Sodium Solution for injection; Infants 1 to 2 months: 25 to 100 mg/kg/day IV/IM divided every 8 hours.
        • Cefazolin Sodium Solution for injection; Adults: 1 g IV every 8 hours for 10 to 14 days.
  • Antibiotics to cover methicillin-resistant Staphylococcus aureus (if there is history of or suspicion for MRSA) or in penicillin- and cephalosporin-allergic patients
    • Outpatient
      • Trimethoprim-sulfamethoxazole double strength (do not use in patients breastfeeding infants younger than 2 months)
        • Sulfamethoxazole, Trimethoprim Oral tablet; Adults: 160 to 320 mg trimethoprim/800 to 1,600 mg sulfamethoxazole PO twice daily for 10 to 14 days.
      • Clindamycin
        • Clindamycin Hydrochloride Oral capsule; Adults: 300 to 450 mg PO every 6 hours for 10 to 14 days.
    • Inpatient
      • Vancomycin
        • Vancomycin Hydrochloride Solution for injection; Neonates 28 weeks gestation and younger and SCr 0.8 to 1 mg/dL: 20 mg/kg IV loading dose, followed by 15 mg/kg/dose IV every 24 hours.
        • Vancomycin Hydrochloride Solution for injection; Neonates 28 weeks gestation and younger and SCr 0.5 to 0.7 mg/dL: 20 mg/kg IV loading dose, followed by 20 mg/kg/dose IV every 24 hours.
        • Vancomycin Hydrochloride Solution for injection; Neonates 28 weeks gestation and younger and SCr less than 0.5 mg/dL: 20 mg/kg IV loading dose, followed by 15 mg/kg/dose IV every 12 hours.
        • Vancomycin Hydrochloride Solution for injection; Neonates older than 28 weeks gestation and SCr 1 to 1.2 mg/dL: 20 mg/kg IV loading dose, followed by 15 mg/kg/dose IV every 24 hours.
        • Vancomycin Hydrochloride Solution for injection; Neonates older than 28 weeks gestation and SCr 0.7 to 0.9 mg/dL: 20 mg/kg IV loading dose, followed by 20 mg/kg/dose IV every 24 hours.
        • Vancomycin Hydrochloride Solution for injection; Neonates older than 28 weeks gestation and SCr less than 0.7 mg/dL: 20 mg/kg IV loading dose, followed by 15 mg/kg/dose IV every 12 hours.
        • Vancomycin Hydrochloride Solution for injection; Infants 1 to 2 months: 40 to 60 mg/kg/day IV divided every 6 hours.
        • Vancomycin Hydrochloride Solution for injection; Adults: 15 mg/kg/dose IV every 12 hours for 10 to 14 days.
• Antifungals (when Candida is suspected or proven with culture)
  • If patient is breastfeeding, treat both her breast and infant’s oral cavity
    • Topical clotrimazole for mother
      • Clotrimazole Topical cream; Adults: Apply to affected skin and surrounding areas twice daily.
    • Oral nystatin for infant
      • Nystatin Oral suspension; Premature Neonates: 100,000 units (1 mL) PO 4 times per day; administer one-half of each dose into each side of the mouth.
      • Nystatin Oral suspension; Neonates and Infants: 200,000 units (2 mL) PO 4 times per day; administer one-half of each dose into each side of the mouth; guidelines recommend to treat for 7 to 14 days.
    • Fluconazole
      • Consider in more severe, recurrent, or refractory fungal infection
      • Data surrounding breastfeeding is minimal
      • Fluconazole Oral suspension; Neonates: 6 mg/kg/dose PO once, then 3 mg/kg/dose PO once daily; other authors recommend extending interval to every 72 hours during first 2 weeks of life and every 48 hours during weeks 3 and 4. Treat for 7 to 14 days.
      • Fluconazole Oral tablet; Adults: 100 to 400 mg PO once daily.
• Recurrent or refractory mastitis
  • Tailor antibiotic therapy based on Gram stain and culture results and on sensitivities of appropriate specimens
• Granulomatous mastitis
  • Treatment regimen generally includes a combination of antibiotic therapy, corticosteroids, and/or methotrexate 
    • Experts recommend the following: 
      • Very mild disease: watchful waiting
      • Relatively mild disease: trial of antibiotics
      • Progressive or more severe disease: steroids with or without methotrexate
  • Antibiotics
    • Granulomatous mastitis: currently, there is no specific recommended antibiotic regimen
    • Cystic neutrophilic granulomatous mastitis: consider covering Corynebacterium
  • Systemic corticosteroids 
    • Oral steroids as first-line treatment have been used with up to 80% success in achieving remission
  • Methotrexate
    • Added to corticosteroids as a corticosteroid-sparing agent

Nondrug and supportive care

Lactational mastitis

• Mainstay of treatment is ongoing breast milk removal through regular continued breastfeeding or pumping, along with rest, fluids, warm compresses, adequate nutrition, and proper hygiene 
  • If feeding difficulties are present, consider referring to a lactation consultant
  • In presence of Candida infections, make sure any infant bottle nipples and/or pacifiers are sterilized regularly and cleaned carefully

Nonlactational infectious mastitis

• Rest, fluids, and warm compresses are recommended for all patients
• Smoking cessation is recommended for patients who smoke, particularly if they have periductal mastitis (duct ectasia) (Related: Tobacco use disorder and smoking cessation)
• Good control of comorbid diseases (eg, diabetes mellitus), is recommended as they are associated with infection, specifically with recurrent infection seen in periductal mastitis

Removal of foreign bodies

• Foreign body may be a nidus for continued infection or may cause mastitis through foreign body reaction
  • Remove foreign bodies when practical
    • Nipple rings
    • Ruptured or leaking breast implants
    • Consider removing intact breast implants in patients with recurrent or refractory mastitis

Granulomatous mastitis 

• Treatment of patients with mild symptoms may be observation and close imaging surveillance alone

Lymphocytic and plasma cell mastitis

• If underlying autoimmune disease is found, mastitis may improve with treatment of underlying condition

Procedures

Surgical resection of affected breast tissue

General explanation

• Surgical incision is made under anesthesia, and inflamed or otherwise damaged tissue is removed

Indication

• Recurrent periductal mastitis
  • Total excision of affected duct and fistulous tract appears to significantly decrease recurrence of mastitis and occurrence/recurrence of abscess 
• Idiopathic granulomatous mastitis
  • Wide local excision of inflamed area is 1 treatment option and may be used in conjunction with medical treatment
  • Success rate for surgery alone is about 65%; one-third of patients require multimodal treatment 
  • Surgery has a shorter healing time than medical therapy alone but a high incidence of wound complication 
• Plasma cell mastitis
  • Focused excision of inflamed area and correction of nipple retraction are effective treatment options 
• Mastitis with necrotic tissue
  • Debridement of necrotic tissue

Contraindications

• Hemodynamic instability
• Unstable cardiopulmonary disease
• Coagulopathy
• Untreated infection
• Recent myocardial infarction

Complications

• Infection
• Bleeding
• Poor wound healing
• Scarring
• Deformity

Interpretation of results

• Surgical success is determined by absence of recurrence or continued inflammation

Breast abscess incision and drainage

General explanation

• Removal of purulent material and fluid from breast abscess
  • May be performed percutaneously with needle using ultrasonographic guidance
  • In abscesses larger than 5 cm or if skin overlying abscess is necrotic or sloughing, consider performing open surgical drainage with irrigation of the abscess cavity 

Indication

• Mastitis with breast abscess

Contraindications

• Hemodynamic instability
• Coagulopathy
• When considering open surgical drainage, unstable cardiopulmonary disease and recent myocardial infarction are relative contraindications

Complications

• Wound infection
• Bleeding
• Scarring
• In open surgical drainage, poor wound healing and cosmetic defects

Interpretation of results

• Resolution of abscess with combined drainage and antibiotics is the measure of success
• Send pus or fluid from abscess for Gram stain, culture, and sensitivities, which are used to guide antimicrobial therapy
• Send pus or fluid from abscess for cytology in cases of unusual infection or other cause of mastitis or abscess

Comorbidities

• Autoimmune diseases in patients with lymphocytic mastitis 
  • Several are associated, including diabetes mellitus, thyroiditis, systemic lupus erythematosus, rheumatoid arthritis, and Sjögren syndrome
  • If underlying autoimmune disease is found, mastitis may improve with treatment of underlying condition 
• HIV in patients with infectious mastitis with unusual pathogens 
  • In HIV-infected patients with infectious mastitis, consider broadening antibiotic or antifungal spectrum due to presence of unusual pathogens such as Bartonella henselae, mycobacteria, Actinomyces, Brucella, Candida, and Cryptococcus species
• Periductal mastitis
  • Smoking cessation may reduce risk of repeat infection (Related: Tobacco use disorder and smoking cessation)

Special populations

• Postmenopausal women
  • Mastitis is uncommon and should raise suspicion for malignancy
• Neonates
  • Mastitis is related to breast tissue hypertrophy caused by exposure to maternal estrogen; after obtaining blood cultures, initial treatment is hospitalization with IV antibiotics (oral antibiotics are not adequate owing to risk of neonatal sepsis)

Monitoring

• Infectious mastitis generally improves with routine treatment within 7 to 10 days 
  • Monitor patients for clinical improvement, including resolution of fever and normalization of breast examination
  • If patient does not improve, initiate further investigations to exclude an underlying carcinoma
• Treat and monitor patients with other forms of mastitis at regular intervals for clinical improvement as well as normalization of ultrasonography and/or mammography findings

Complications and Prognosis

Complications

• Breast abscess
  • Localized collection of purulent material within the breast
  • Occurs in up to 11% of women with mastitis 
    • Risk factors
      • Obesity
      • Smoking
    • Typical age range is 18 to 50 years, but abscesses tend to occur toward the end of reproductive years 
      • 50% of infants with neonatal mastitis will develop a breast abscess 
    • Treatment includes antibiotics and drainage
      • Drainage is most commonly percutaneous and performed using ultrasonographic guidance
      • Rare large abscesses may require surgical incision and drainage
    • About 40% of abscesses are polymicrobial 
      • Same causative organisms as mastitis
      • Anaerobes are seen in 50% of these abscesses and are more likely to be isolated in patients who smoke
    • Abscesses may be recurrent, owing to plugging of lactiferous ducts
      • Excision of blocked lactiferous duct prevents recurrence
  • Mammary fistula
    • Associated with subareolar abscess and plugged lactiferous duct
    • Occurs in up to 2% of women with mastitis 
    • Requires surgical excision of fistula, feeding abscess, and plugged lactiferous duct 
• Breast scarring 
  • Surgical intervention other than needle aspiration may cause a postoperative scar
• Breast deformity 
  • Recurrent infections, tuberculous, and granulomatous mastitis can cause significant breast deformity

Prognosis

• Prognosis for routine infectious lactational and nonlactational mastitis without abscess is excellent
• Prognosis for recurrent and chronic forms of mastitis depend on underlying pathology and development of complications (eg, fistulae)
  • Surgical management may be required for some forms of recurrent and chronic mastitis
  • Long-term use of immune-modulating medications may be required in some forms of chronic mastitis

Screening and Prevention

Prevention

• Various strategies—including breastfeeding education, prophylactic antibiotics, topical ointments, and antisecretory factor cereal—have not been shown to effectively prevent mastitis 
  • Studies available to review were generally of low quality with limited findings
• Given risk factors for lactational mastitis, appropriate preventative measures include: 
  • Frequent and regular breastfeeding
  • Prompt management of feeding and nipple attachment difficulties
  • Avoidance of tight or constricting bras and clothing
  • Avoidance of manual breast pump use
  • Prompt attention to cracked nipples to promote healing

Summary

• Mastitis is inflammation of the breast tissue. It occurs most often in women who are breastfeeding, but it can also affect non-breastfeeding women and some men.
• This condition is usually caused by a bacterial infection.
• This condition may be treated with hot and cold compresses, medicines, self-care, and certain breastfeeding strategies.
• If you were prescribed an antibiotic medicine, take it as told by your health care provider. Do not stop taking the antibiotic even if you start to feel better.

Sources

Scott-Conner CE et al: The diagnosis and management of breast problems during pregnancy and lactation. Am J Surg. 170(4):401-5, 1995  Reference