Multiple hereditary infundibulocystic basal cell carcinomas - A genodermatosis different from nevoid basal cell carcinoma syndrome

Background: Infundibulocystic basal cell carcinoma is a recently described distinctive clinicopathologic variant of basal cell carcinoma. Histopatholo gic differential diagnosis among infundibulocystic basal cell carcinoma, tr ichoepithelioma, and basaloid follicular hamartoma has generated controvers y in the literature. Observations: Members of 2 families with multiple infundibulocystic basal c ell carcinomas are described. Each patient showed multiple papular lesions, mostly located on the face, No patient showed palmar pits or jaw cysts. Fo rty-two cutaneous lesions from 5 patients were studied histopathologically. Thirty-nine lesions were infundibulocystic basal cell carcinomas. This cli nicopathologic variant of basal cell carcinoma consists of a relatively wel l-circumscribed basaloid neoplasm composed of buds and cords of neoplastic cells arranged in anastomosing fashion and with scant stroma. Some of the n eoplastic cords contain tiny infundibular cysts filled by cornified cells w ith abundant melanin. Linkage analysis in family 2 was performed using poly morphic markers (D9S196, D9S280, D9S287, and D9S180), and the affected memb ers shared the same haplotype. Loss of heterozygosity analysis was performe d in 2 affected members of this family from whom tumoral DNA was available, and although these individuals were constitutively heterozygous for D9S196 , they did nor show loss of heterozygosity for this marker in their neoplas ms. Conclusions: Multiple hereditary infundibulocystic basal cell carcinomas re present a distinctive genodermatosis different from multiple hereditary tri choepitheliomas and nevoid basal cell carcinoma syndrome. We propose clinic al and histopathologic criteria to distinguish infundibulocystic basal cell carcinoma from trichoepithelioma, basaloid follicular hamartoma, and folli culocentric basaloid proliferation.