A Rare Case of Rectal Mixed Adeno-Neuroendocrine Carcinoma (MANEC) with Liver Metastasis
Abstract Introduction/Objective Mixed Adeno-Neuroendocrine Carcinoma (MANEC) is a rare subtype of colorectal cancer which was recognized and described by the world health organization (WHO) in 2010. It was defined as malignant neoplasms in which each component represents at least 30% of the lesion. In this abstract, we present a case of mixed adeno-neuroendocine carcinoma of the rectum with metastasis of the neuroendocrine component to the liver. We discuss the histomorphological and immunohistochemical features of this tumor. Methods/Case Report A 64-year-old male presented with abdominal pain in the right upper quadrant area. An abdominal CT scan showed multiple nodules in the liver as well as a mass lesion in the rectum. Liver needle core biopsy revealed infiltrating nests of atypical cells with marked pleomorphism, a variable amount of cytoplasm, and prominent nucleoli. Mitotic activity and necrosis were seen. By immunohistochemical staining, the tumor cells were negative for CK7 and CK20, positive for CD56, and partially positive for CDX2. Although glands formation was not seen; however, given the positivity of CDX2 as well as the colonic mass, mismatch protein analysis (MMR) was performed and it was intact. These findings were consistent with poorly differentiated high-grade neuroendocrine carcinoma. The rectal mass was excised through colonoscopy and revealed invasive carcinoma with morphology similar to that of the liver biopsy in addition to a vague glandular differentiation. Tubulovillous adenoma was also seen. On immunohistochemical staining, the invasive component was positive for CD56, synaptophysin, and chromogranin A, partially positive for CDX2, and negative for CK20, consistent with the neuroendocrine component. The adenoma was positive for CK20, and CDX2, and negative for CD56. Rare positivity was seen by synaptophysin and chromogranin A. The carcinoma and the adenoma were both positive for P53. The neuroendocrine carcinoma comprised 40-50% of the tumor. Results (if a Case Study enter NA) NA Conclusion Only a few cases of Mixed Adeno-Neuroendocrine Carcinoma (MANEC) were reported. We add a new case with liver metastasis. The systematic application of immunohistochemical studies aided in the recognition of each component of the neoplasm.