Amphicrine carcinoma of the right colon, a report of a case and review of literature

Abstract

Mixed neuroendocrine and non-neuroendocrine neoplasms, recently recognized in the WHO classification as (MiNEN), are rare tumors of the gastrointestinal tract. These tumors are composed of two distinct cellular components; a well- or poorly differentiated neuroendocrine tumor and a non-neuroendocrine tumor, usually in the form of an adenocarcinoma, either admixed with or adjacent to one another. A rarer phenotype is a tumor in which the endocrine and epithelial cell features occur within the same cell; i.e. amphicrine carcinoma. Herein, we report the case of an 80-year-old female patient who presented with melena, and who, on biopsy was diagnosed as amphicrine carcinoma that was mismatch repair deficient (MMRd) with loss of MLH1/PMS2 nuclear expression by immunohistochemistry. The histological and immunohistochemical findings of this rare entity are presented with review of pertinent literature.

Keywords: Amphicrine carcinoma; colonic adenocarcinoma; mismatch repair deficiency; neuroendocrine carcinoma; synaptophysin.

Figure 1.

The morphology and immunoprofile of the original colonic biopsy. (a) There is proliferation of sheets of cells with signet-ring like appearance that contain intracytoplasmic mucin, highlighted by Diastase PAS (Inset). (b) CDX-2 immunostain is positive in the tumor cell nuclei. (c) Synaptophysin is positive in the tumor cell cytoplasm. (d) INSM-1 is positive in tumor cell nuclei. (e) and (f) Loss of PMS2 and MLH1 nuclear staining in the tumor cells, in the presence of internal positive control, consistent with MMR-deficient tumor. (g) BRAF p. V600 E shows strong diffuse cytoplasmic staining.