Pediatric Non-Neural Granular Cell Tumor With Unexpected Molecular Identity: A Case That Challenges Classification.

Abstract

A 7-year-old boy presented with a 3-year history of a slow-growing superficial cutaneous nodule adjacent to the right acromion, with subsequent development of a second subcutaneous mass near the right scapula. Biopsy of the primary lesion revealed a rare non-neural granular cell tumor (NNGCT) lacking S100 expression, distinguishing it from classic granular cell tumors (GCT), and molecular profiling identified a DCTN1::ALK fusion alongside an ATP6AP2 frameshift mutation, the latter reported predominantly in GCT. To our knowledge, this is the first documented NNGCT harboring both alterations, suggesting potential biologic overlap between NNGCT and GCT while expanding the current framework of granular cell tumor classification. This case also highlights the reported potential for recurrence and multifocal disease or regional spread in NNGCT, supporting complete surgical excision with long-term follow-up.