Colorectal large-
cell neuroendocrine carcinomas (NECs) are extremely rare and have very poor
prognosis compared to
adenocarcinomas. A 74-year-old man presented with
abdominal pain,
diarrhea and
hematochezia. The histopathologic
report of colonoscopic
biopsy performed at a local clinic was a poorly differentiated
carcinoma. An abdominopelvic computed scan revealed irregularly enhanced wall thickening at the
sigmoid colon with regional fat stranding and lymphnode enlargement. He underwent a laparoscopic high anterior resection with selective peritonectomy for
peritoneal carcinomatosis, intraoperative
peritoneal irrigation chemotherapy, and early postoperative intraperitoneal
chemotherapy for 5 days. The
tumor had a high proliferation rate (mitotic count > 50/10 HPFs and 90% of the Ki-67 index) and
lymph-node
metastases had occurred. On
immunohistochemistry, the
tumor cells expressed CD56 and
synaptophysin. Large-
cell NEC was confirmed. Systemic
chemotherapy with
cisplatin/
etoposide was done. The
patient is still alive after 3 years with no evidence of
recurrence.