HETEROGENICITY OF NEUROENDOCRINE TUMOURS AND ITS SIGNIFICANCE – A CASE SERIES

Abstract

Neuroendocrine neoplasms are a heterogeneous group of tumours that share characteristic neuroendocrine morphology and immunophenotype but differ considerably by anatomical site, grading, and biological behaviour. This case series was conducted in the Department of Pathology in a tertiary care health centre, Chengalpattu, Tamil Nadu, to illustrate the morphologic and immunohistochemical spectrum of neuroendocrine tumours across different organs. Five cases were studied, comprising an ileal neuroendocrine tumour, a duodenal neuroendocrine tumour, a pancreatic neuroendocrine tumour, a pituitary neuroendocrine tumour, and an adrenal pheochromocytoma. Histopathological examination in all cases showed typical neuroendocrine features, including nesting, trabecular, cord-like, lobular, rosette-like architecture. Individual tumour cells showed round to oval nuclei and finely stippled salt-and-pepper chromatin. Immunohistochemistry demonstrated synaptophysin and chromogranin positivity in all cases, confirming neuroendocrine differentiation. The ileal, duodenal, and pancreatic tumours showed low mitotic activity and low Ki-67 indices (1–2% or 2%), supporting a diagnosis of well-differentiated Grade 1 neuroendocrine tumour. The pituitary lesion also showed low proliferative activity and was classified as pituitary neuroendocrine tumour with low-grade features. In contrast, the adrenal pheochromocytoma showed larger tumour cells arranged in nests (Zell-ballen pattern), higher mitotic activity (5–10/10 HPF), and a Ki-67 index of 5–10%, correlating with its more aggressive clinical behaviour. The series highlighted both the shared diagnostic hallmarks and the site-specific heterogeneity of neuroendocrine neoplasms, underscoring the importance of integrating morphology, immunohistochemistry, and proliferation indices for accurate diagnosis and classification.