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What are the cross sectional imaging features that help to distinguish colorectal lymphoma from adenocarcinoma?
Comparison of Cross sectional Imaging Features of Colorectal Lymphoma and Colorectal Adenocarcinoma
| LYMPHOMA | ADENOCARCINOMA | |
|---|---|---|
| Effect on adjacent soft tissues | General preservation of surrounding visceral fat | May be associated with invasion of adjacent visceral fat and other organs |
| Bowel obstruction | No | Yes |
| Bowel lumen | Aneurysmal dilation | Annular narrowing |
| Wall thickening | Mild, smooth, concentric | Severe, irregular, eccentric |
| Transition from normal to abnormal wall thickness | Gradual | Abrupt with shouldering |
| Length of affected segment | Segmental or focal | Focal (<5 cm) |
| Lymphadenopathy | Bulky mesenteric and/or retroperitoneal lymph nodes are common | Enlarged lymph nodes tend to be less bulky than in lymphoma, predominantly in pericolic or mesenteric locations |
- Modern MDCT scanners, which allow thinner collimation and faster scanning, can sometimes identify small tumours as avidly enhancing submucosal lesions. Detection is improved if water is given as an oral contrast and multiplanar reconstructions are performed.
- Low attenuation oral contrast permits optimal delineation of enhancing tumour against the bowel lumen. Dual-phase (arterial and venous) imaging allows optimal imaging of the arteries and veins.
- CT enteroclysis with multiplanar reconstruction has advantages of enteroclysis with morphologic imaging capabilities of helical CT, which lead to an improved detection rate. In a recent study, MDCT detected small bowel carcinoids with a sensitivity of 100% and specificity of 96.2%.
- Whereas, CT may not always identify small tumours, it is excellent at demonstrating mesenteric extension and liver metastases.
- Carcinoid metastases to the liver are typically hypervascular on early arterial images, showing avid enhancement and becoming isoattenuating to the liver parenchyma on delayed phases
