High Grade / Poorly Differentiated Neuroendocrine Carcinoma of the Gastrointestinal Tract
Differential Diagnosis
- Small Cell Endocrine Carcinoma
- Metastatic carcinoma must always be ruled out, especially from the lung
- TTF1 is positive in 16% of GI small cell carcinomas
- Clinical correlation is usually required
- Metastatic carcinoma must always be ruled out, especially from the lung
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Large Cell Endocrine Carcinoma vs Carcinoma NOS
- Ddiagnosis of large cell endocrine carcinoma requires both morphologic and immunohistologic features as described above
- It is not clear that large cell endocrine carcinoma presently behaves differently from small cell carcinoma and high grade adenocarcinoma
- The distinction may be worthwhile for advances in therapy
| Colorectal Undifferentiated Carcinoma NOS | Colorectal Small Cell Neuroendocrine (Undifferentiated) Carcinoma |
| Chromogranin and synaptophysin at most focal or scattered | Chromogranin or synaptophysin may be negative or positive |
| Vesicular nuclei | Chromatin finely granular, stippled |
| Prominent nucleoli | Inconspicuous nucleoli |
| Pleomorphic large cells | Uniform small to medium size cells |
| Colorectal Undifferentiated Carcinoma NOS | Colorectal Large Cell Neuroendocrine Carcinoma |
| Chromogranin and synaptophysin at most focal or scattered | Chromogranin or synaptophysin must be positive in at least 20-50% of cells |
| Vesicular nuclei | Chromatin finely granular, stippled |
| Prominent nucleoli | Inconspicuous nucleoli |
| Does not form rosettes | May form rosettes |
