Poorly Differentiated Large Cell Neuroendocrine Carcinoma of the Colon: A Case Report

Colon cancer is one of the most common diagnoses of cancer and a leading cause of death in America. Large cell neuroendocrine tumors are a very uncommon type of colon cancer that tends to have a poor prognosis. Usually, these tumors are only found at the time of metastasis making them even more difficult to treat. A 65-year-old female presented with worsened generalized abdominal pain associated with abdominal distention. She had not had a bowel movement in over a week and did not have any flatulence. She had a colonoscopy four years prior that was normal. Physical examination was significant for abdominal distention and a large right-sided palpable mass in her abdomen with generalized tenderness. A CT scan showed a large irregular mass at least 9.8 x 10.5 cm at the mid to distal ascending colon resulting in significant colonic narrowing significant for a large bowel obstruction. The CT also demonstrated suspicious nodules in the lung, lesions in the liver, and lymphadenopathy. She had an exploratory laparotomy with an extended hemicolectomy to remove the mass. Pathology revealed the mass was neuroendocrine carcinoma, a large cell subtype, that was poorly differentiated with involvement of at least 32 of 34 lymph nodes. This tumor was positive for AE1/AE3, CEA, CK20, and synaptophysin. Ki-67 showed 70% positivity. TTF1 was negative and ruled out a primary lung tumor. Microsatellite immunostains were positive for MLH-1, MSH-2, MSH-6, and PMS2. The patient was started on Carboplatin AUC6 and Etoposide 100mg/m² in three-week intervals. Pegfilgrastim was also added to her treatment plan every 21 days. This is a review of a female who presented with colonic obstruction that was found to be poorly differentiated large cell neuroendocrine carcinoma after a previous negative colonoscopy.