What are some benign cystic lesions that may involve the spleen?
Cyst, pseudocyst, lymphangioma, pyogenic abscess, hydatid cyst, fungal microabscess, and mycobacterial microabscess.
Cysts (lined by epithelium), pseudocysts (lined by fibrotic tissue), and lymphangiomas typically have fluid attenuation (0 to 20 HU), low T1-weighted and very high T2-weighted signal intensity, thin walls, and no solid enhancement. Peripheral calcifications are sometimes seen in pseudocysts, and thin internal septations are often seen in lymphangiomas.
Pyogenic abscesses have low attenuation, low T1-weighted and high T2-weighted signal intensity, internal septations, and thick rim enhancement, sometimes with very low attenuation and very low signal intensity foci of gas.
Hydatid cyst due to Echinococcus granulosus parasitic infection typically contains multiple daughter cysts creating a multilocular appearance along with a low signal intensity rim, which may be calcified, usually without enhancement. Some loculations may have increased attenuation or T1-weighted signal intensity. The presence of internal collapsed membranes (the “water lily” sign) is considered to be pathognomonic.
Microabscesses due to fungal or mycobacterial infection tend to be multiple, <1 cm in size, and have low attenuation, low T1-weighted and high T2-weighted signal intensity relative to spleen, and rim enhancement. These are most often due to candidiasis in immunocompromised patients and are commonly seen to also involve the liver.
