Desmoplastic hairless hypopigmented nevus (DHHN). A distinct variant of giant melanocytic nevus

Desmoplastic hairless hypopigmented nevus (DHHN) is the name Ruiz-Maldonado et al. gave to a new variant of giant congenital melanocytic nevus characterized clinically by a hard ligneous consistency, absence of hair and progressive loss of pigment. Histologically, dermal fibrosis consistent with desmoplasia is a predominant feature. We describe a 6-year-old boy with a hard hairless pigmented congenital nevus involving the lumbosacral area, buttocks, perineum and scrotum. During the first years of life, the nevus showed a progressive reduction in colour, size and consistency. These changes continued until the age of four when a well-demarcated tumour appeared, within the nevus, on the right buttock. Resection of this outgrowth was performed. Histologically, nevus cells of normal appearance between thick collagen bundles were present. Immunostaining revealed S 100+, Vim+, HMB45-results. The nevus has continued to involute to date. An immune response against the melanocytes of the nevus may explain this type of evolution.