1653 Large Cell Neuroendocrine Carcinoma of the Colon

INTRODUCTION: Neuroendocrine carcinomas heterogeneous group of tumors with variable clinical presentation and prognosis. Gastrointestinal neuroendocrine carcinomas are further divided into two types; small cell or large cell based on mitotic rate and or Ki-67 labeling by WHO or European Neuroendocrine Tumor Society guidelines. Large cell neuroendocrine carcinomas (LNEC) of primary colorectal origin are extremely rare and represent 0.25% of all colorectal cancers. LNEC are malignant and aggressive tumors which present in an advanced stage and median overall survival time is 4–16 months. LNEC can occur within the entire gastrointestinal tract and or biliary tract but are typically found within the colon, stomach and or rectum. Here, we report LNEC to highlight its clinical course and to expand clinician knowledge regarding this rare cancer. CASE DESCRIPTION/METHODS: 82-year-old male who initially presented to his primary care doctors office with 4-month history of 20-pound unintentional weight loss with associated vague left lower quadrant abdominal pain. Computed Tomography of the abdomen/pelvis revealed mass-like mucosal thickening measuring approximately 5.9 cm × 6.5 cm involving the distal transverse/proximal descending colon and with innumerable hypodense lesions throughout the liver consistent with diffuse metastatic disease. Colonoscopy revealed circumferential fungating partially obstructing large mass in the within the mid-transverse colon. Histopathologic report from the endoscopic biopsy showed positive staining for pancytokeratin and synaptophysin, which was consistent with a large cell neuroendocrine carcinoma. Patient was evaluated by oncology and has started receiving carboplatin and etoposide chemotherapy for palliative purposes. DISCUSSION: LNEC rare subtype of neuroendocrine carcinomas, which are aggressive and often present in an advanced stage. Early detection and identification is essential as this malignancy has different treatment implications when compared to adenocarcinoma. Interestingly, extrapulmonary neuroendocrine tumors resemble small cell lung cancer where carboplatin and etoposide have established utility due to high mitotic rate. This is the treatment option chosen for our patient. Further studies will need to be done to determine optimal treatment regimens for this rare disease.