Primary cutaneous ganglioneuroma: anatomico-clinical study of 4 cases with focus on Merkel cells.

Cutaneous ganglioneuromas (CGNs) are exceptional. We aim to describe the anatomico-clinical profile of primary CGN and report 4 cases. Patients were 2 men and 2 women aged 53 to 76 years, who had flesh-colored nodules on the back, associated with adjacent keratotic changes, that is, epidermal nevus (1 case) or seborrheic keratosis (3 cases). Histopathology showed ganglion cells within a proliferation of Schwann cells. The epidermis was acanthotic, associated with sebaceous induction in 2 cases, with follicular hyperplasia as in fibroepithelial tumors (1 case) or with tricholemmoma (2 cases). Cytokeratin-20 immunostaining showed Merkel cells in the epidermis. A higher density of Merkel cells was observed in BerEP4+ follicular structures. Along with 16 published cases, our study indicates that a nodule associated with seborrheic keratosis on the back may represent a CGN, a complex mesenchymal and epidermal/follicular lesion of neuroectodermal lineage, associating neuronal proliferation and Merkel cell hyperplasia with follicular induction.