Expression status of Neurotrophic Tropomyosin Receptor Kinase (NTRK) in pheochromocytoma and its association with clinicopathological factors.

, mediates neurotrophin signaling and contributes to cellular differentiation. Although TrkA expression has been observed in pheochromocytoma, its pathological significance remains unclear. In this study, we examined 31 surgically resected pheochromocytomas using immunohistochemistry for NTRK, S100, tyrosine hydroxylase (TH), dopamine β-hydroxylase (DBH), phenylethanolamine N-methyltransferase (PNMT), Ki-67, and succinate dehydrogenase complex iron sulfur subunit B (SDHB). The immunoreactive score was used to semiquantitatively evaluate the expression of NTRK and catecholamine-synthesizing enzymes, and their correlations with clinicopathological factors, including PASS and GAPP scores, were analyzed. NTRK immunoreactivity was detected in approximately 80% of tumors. High NTRK expression was significantly positively correlated with S100-positive sustentacular cells, TH, and DBH, but not with PNMT. In contrast, NTRK expression was inversely correlated with the Ki-67 labeling index. NTRK expression did not correlate with clinicopathological variables, PASS or GAPP scores, or SDHB status. These findings suggest that NTRK expression reflects structural and functional differentiation in pheochromocytoma, characterized by preserved sustentacular cell networks and catecholamine synthetic capacity rather than indicating malignant potential. Therefore, NTRK may serve as a differentiation-associated marker in pheochromocytoma, and further molecular investigations are warranted to elucidate its mechanistic role in chromaffin cell biology.