Large cell neuroendocrine carcinoma in the unusual location of the descending colon

A Rare Case of Metastatic Poorly Differentiated Neuroendocrine Tumor Arising From the Sigmoid Colon in an Active Duty Service Member

Neuroendocrine tumors (NET) are rare malignancies that contain neural and endocrine cells with a median age of diagnosis of 63 years. NETs are typically located in the gastrointestinal (GI) tract, the pancreas, or the lungs. Within the GI tract, the most common locations for NETs are the small bowel, appendix, or rectum. They are often asymptomatic and found incidentally on imaging or during procedures. NETs arising from the left side of the colon are very uncommon. While most NETs are well-differentiated by histology and are slow growing, 7% are poorly differentiated and usually progress rapidly. While rare, it is vital to be vigilant for this reason We present such a case of poorly differentiated metastatic NET of the sigmoid colon in a young active duty service member.

Multifocal diffuse large cell neuroendocrine carcinoma of the colon

Background

Large cell neuroendocrine carcinomas (LCNEC) of the colon are an extremely rare and aggressive type of colorectal cancer. While multifocality is more frequently seen in small intestine NECs, no cases of multifocal NEC of the colon have been reported before.

Aim

A 69-year-old male patient presented with abdominal pain. Colonoscopy revealed a necrotic-polypoid mass in the sigmoid colon and the biopsy result was reported as malignant epithelial tumor. Laparoscopic anterior resection was performed with the preliminary diagnosis of colon adenocarcinoma. Histopathological examination revealed three polypoid tumors, the largest of which was 4 cm, in the sigmoid colon. Immunohistochemical examination showed positivity for synaptophysin, chromogranin, and CDX2. High Ki67 proliferation index, high mitosis, and widespread p53 expression were observed in all tumors. With these findings, a diagnosis of multifocal large cell NEC was made. To the best of our knowledge, this is the first report describing a case of multifocal large cell NEC of the colon.

Relevance for Patients

LCNECs of the colon are very aggressive. Here, we report for the first time a case of multifocal LCNEC. In a short period of 1 month after the surgery, new widespread metastases were detected in the liver. Therefore, these tumors should be followed more closely than usual for early treatment.