Colorectal mixed adeno-neuroendocrine carcinomas

Abstract

Mixed adeno-neuroendocrine carcinomas (MANEC) are rare gastrointestinal neoplasms most commonly diagnosed in the large bowel. They contain mixed exocrine and endocrine components and for diagnosis at least 30% of either component must be identi-fied. We present two recent cases, the first of which was a 69-year-old male who presented with anaemia and weight loss and was found to have a rectal tumour. He received combined chemo-radiotherapy and subsequent surgery revealed a 15 mm MANEC invading into the perirectal tissue. The tumour showed radiation-induced changes with neuroendocrine carcinoma adjacent to ad-enocarcinoma. The second case was a 75-year-old male who presented with obstructive symptoms and a palpable abdominal mass. Following surgery, he was found to have a 95 mm MANEC in the ascending colon invading into the pericolic tissue. Both cases were confirmed using neuroendocrine immunohistochemical markers. Positive staining of the neuroendocrine components was seen with at least two of CD56, synaptophysin and chromogranin. The current World Health Organization (2010) classification recognises that size >20 mm, invasion of the muscularis propria, lymphatic invasion and atypical histology are significant risk factors for malignant behaviour. The two cases presented contain most, if not all of these factors.