well-differentiated neuroendocrine tumor
Low to intermediate-grade neuroendocrine tumor maintaining organized cellular architecture and expressing neuroendocrine markers.
Full Definition
Well-differentiated neuroendocrine tumor represents a category of neuroendocrine neoplasms characterized by organized histological architecture that resembles normal neuroendocrine tissue, with cells arranged in nests, ribbons, or trabecular patterns. These tumors maintain expression of neuroendocrine markers such as chromogranin A and synaptophysin, and have relatively low proliferative activity (Ki-67 typically ≤20% and mitotic count ≤20 per 2 mm²). Well-differentiated neuroendocrine tumors correspond to WHO Grades 1 and 2, generally have better prognosis than poorly differentiated neuroendocrine carcinomas, and may be amenable to somatostatin analog therapy. The term reflects both morphological characteristics and biological behavior, distinguishing these tumors from high-grade neuroendocrine carcinomas.
Usage
Usage note: Hyphenate 'well-differentiated' when used as compound modifier; contrast with poorly differentiated types.
In Context
- "Histology revealed a well-differentiated neuroendocrine tumor with Ki-67 index of 5% and low mitotic count." — Pathology report
- "The patient's well-differentiated neuroendocrine tumor showed excellent response to octreotide therapy." — Clinical follow-up