Abstract

Basaloid follicular hamartomas (BFHs) are benign neoplasms of the hair follicle that present as small skin-colored papules on the face, scalp, and occasionally, trunk. BFHs can have significant histologic overlap with infundibulocystic basal cell carcinomas (BCCs). Notably, some authors have suggested that the terms “infundibulocystic BCC” and “BFH” are synonymous for the same tumor with indolent behavior.4 Both BFHs and infundibulocystic BCCs have been reported to be associated with both PTCH1 and SUFU gene mutations.1–3 We present two sisters with multiple dome-shaped, skin-colored, small papules on the central face, reportedly present for years. Multiple biopsies from one of the sisters demonstrated endophytic basaloid neoplasms with areas of keratinization and follicular differentiation. On select specimens, immunohistochemical staining for Ber-EP4 was negative with a very low Ki67 proliferative index and CK20 demonstrating rare Merkel cells. These findings were diagnosed as basaloid follicular hamartomas. Notably, the other sister had several lesions diagnosed as infundibulocystic BCC at an outside institution. Genetic testing identified a SUFU c.124dup (p.Arg42Profs*6) pathogenic variant in both sisters. The association between infundibulocystic BCCs, BFHs and SUFU mutation in these presented cases prompts further consideration that SUFU mutation may result in an incomplete presentation of Gorlin’s syndrome or perhaps a distinct syndrome. Awareness of this clinicopathologic spectrum is important for dermatopathologists and dermatologists as it may elucidate a particular phenotype of indolent basaloid neoplasms. and help patients avoid unnecessary surgical procedures. Additionally, as SUFU lies downstream of smoothened (SMO), vismodegib is unlikely to be effective in this subset of patients.

Financial Disclosure: No current or relevant financial relationships exist.