| [ Summary ] |
Colorectal endocrine cell carcinomas are rare but highly aggressive neoplasms with poor prognoses, making diagnosis through histopathologic examinations essential. For pathological diagnosis, the following issues should be considered. 1) The histopathological diagnosis of colorectal endocrine cell carcinomas requires high-grade carcinomas with some morphological features and sufficient endocrine cell differentiation confirmed by immunohistochemistry. Endocrine cell carcinoma in the Japanese classification primarily corresponds to neuroendocrine carcinoma (NEC) by the WHO classification. However, the basis of classification is different between the two systems. 2) Distinction from poorly differentiated carcinomas without endocrine features is often difficult, compelling us to perform immunohistochemistry for suspected cases. The results of immunohistochemistry should be interpreted systematically. 3) Colorectal endocrine cell carcinomas often form tumors with concomitant adenoma and/or adenocarcinoma components. Because even the presence of a small amount of endocrine cell carcinoma component (including cases diagnosed as adenocarcinoma based on the WHO criteria) could influence the prognosis, it should be diagnosed and reported definitely. 4) In the histopathologic interpretation of biopsy materials, we should give attention to somewhat different impressions of histologic appearance, and, often failing to obtain the neoplastic tissue in biopsy (obtaining only adenoma and/or adenocarcinoma components, or only necrotic and/or nonneoplastic mucosa tissues) |