Segmental basaloid follicular hamartomas derive from a post‐zygotic SMO p.L412F pathogenic variant and express hair follicle development‐related proteins in a pattern that distinguish them from basal cell carcinomas

Abstract

Basaloid follicular hamartomas (BFH) are benign small basaloid skin tumors that can present as solitary or multiple lesions. Congenital BFH lesions arranged in a segmental distribution have been described, suggesting they derive from a somatic postzygotic mutational event. Previously, BFH were described in Happle-Tinschert syndrome, which results from a post-zygotic SMO variant and is characterized by seg-