A Rare Variant of High-Grade Neuroendocrine Tumor in a Healthy African American Male

Abstract

Neuroendocrine tumors (NET) are a set of rare tumors composed of glandular endocrine cells typically found in the pancreas, intestine, or lungs. However, the incidence of NET is growing, from 2.48 to 2.586 per 100,000 per year. This growing prevalence stresses the importance in making NET a part of the differential for gastrointestinal (GI) symptoms. Neuroendocrine cells comprise of glandular endocrine cells that reside in the epithelial lining of the GI tract. Classified as either high grade or low grade, NETs are a disruption of these cells. In this case, we present a male with a rare variant of high grade NET. A 51 year old African American male with a past medical history of hypertension and benign prostatic hyperplasia presents to Larkin Community Hospital with abdominal pain for 6 weeks. He complained of constipation for one month with melena, hematochezia, nausea, and abdominal pressure with eating. Abdominal imaging showed multiple heterogeneous retroperitoneal and mesenteric lymph nodes with central hypodensities and rim enhancements, moderate thickening of the gastric antrum, and pylorus. Pathology of left retroperitoneal lymph nodes showed moderately differentiated carcinoma embedded in fibrous tissue. Tumor cells stained positive for CDX2 and negative for CK20, PSA, TTF1. Colonoscopy revealed a friable, ulcerated lesion in the proximal transverse colon. Biopsy showed an infiltrating high grade/large cell NET similar in morphology to the retroperitoneal lymph node biopsy and fragments of tubulovillous adenoma. Transverse colon resection showed extensive lymphovascular invasion, metastatic carcinoma involving 14/14 lymph nodes with extranodal extension and multiple tumor deposits in pericolonic tissue. NETs are defined based on their anatomic location, such as the pancreas, intestine, or lungs. A positive CDX2 suggests a GI origin and TTF1 suggests a pulmonary origin. NETs are comprised of Kulchitsky cells, which help intestinal motility and secretion. Due to the slow growth rate of NET and nonspecific symptoms, diagnosis is delayed until acute bowel obstruction or liver metastases leading to carcinoid syndrome occurs. Two thirds of NETs are carcinoid tumors and one third are of unknown primary origin including high grade/large cell NET as seen in this case. As a result of increasing NET prevalence, it is now imperative to remember to incorporate NETs in the differential diagnosis of atypical masses to prevent delayed diagnosis and treatment.Figure: A friable ulcerated lesion visualized in the proximal transverse colon.Figure: Another view of the friable ulcerated lesion visualized via colonoscopy.