Familial seborrhoeic keratosis associated with multiple ‘pure reticulated acanthomas’ and infundibulocystic basal cell carcinomas

Abstract

Background: A variety of genodermatoses with multiple cutaneous tumors with germline genetic alterations such as Gorlin syndrome with PTCH1 gene mutations have been described. Other cutaneous syndromes have been associated with somatic gene mutations, such as FGFR3 in familial seborrhoeic keratosis. Objective: We describe the clinical, dermoscopic, and histopathological features of multiple cutaneous lesions, mostly infundibulocystic basal cell carcinomas and reticulated acanthomas, present in a family affected by familial seborrhoeic keratosis. In addition, we tested for possible germline alterations in the FGFR3 and PTCH1 genes. Methods: Ten members of one family were clinically examined. Ninety-two skin biopsy specimens were evaluated. Blood samples of three subjects were analyzed for FGFR3 and PTCH1 germline mutations. We review the literature concerning genetic FGFR3 alterations in seborrhoeic keratosis. Results: Subjects of all generations affected by familial seborrhoeic keratosis also presented other skin tumors which corresponded histologically to reticulated acanthomas without apocrine or sebaceous differentiation as well as infundibulocystic basal cell carcinomas. In addition, two novel germline mutations, p.Pro449Ser in FGFR3 gene and p.Pro725Ser of PTCH1 gene were identified in two sisters. Conclusion: We characterize for the first time the clinical, dermoscopic and histopathological features of multiple reticulated acanthomas without apocrine or sebaceous differentiation, for which we propose the term “pure reticulated acanthoma”, and infundibulocystic basal cell carcinomas, associated with familial seborrhoeic keratosis. We identified FGFR3 and PTCH1 germline polymorphisms whose influence in the development of reticulated acanthomas is unknown.