Neural Crest-Derived Co-localization: A Case of Granular Cell Tumor Arising Beneath a Nevus Spilus.

Granular cell tumors (GCTs) are rare neoplasms believed to originate from Schwann cells, exhibiting immunohistochemical and ultrastructural features consistent with neural crest derivation. Similarly, a nevus spilus (NS) is a pigmented skin lesion composed of lentiginous background macules with superimposed darker macules or papules, also thought to arise from neural crest-derived melanocytes. We report a unique case of a 27-year-old female who presented with a painful subcutaneous nodule on the left medial midback, overlaid by an NS. Surgical excision revealed a lesion consistent with a GCT based on histopathologic evaluation. To our knowledge, this is one of the few reported cases demonstrating spatial co-localization of a GCT and NS. This case raises the possibility of a shared embryologic origin contributing to the concurrent development of both lesions in the same anatomic location. Further research is needed to explore whether this reflects a coincidental overlap or an underlying developmental association between neural crest-derived cutaneous proliferations.