Blue Nevi and Variants: An Update

CONTEXT: Blue nevi are a subset of melanocytic proliferations containing cells reminiscent of the embryonal neural crest-derived dendritic melanocytic precursors. They are common specimens in a general pathology practice, but some of their rare variants may pose diagnostic difficulty. Recent molecular studies provide new insights into genetics of blue nevi. OBJECTIVE: To critically review clinical and histologic features of blue nevi with emphasis on diagnostic problems and rare variants, as well as to provide an update on the pathogenesis of blue nevi. DATA SOURCES: Published peer-reviewed literature and personal experience of the authors. CONCLUSIONS: Challenging areas in diagnosis of blue nevi include recognition of amelanotic, desmoplastic, atypical, and malignant variants of blue nevus. Recent data show that mutations in genes responsible for common nevi or melanomas such as BRAF , NRAS , or c- kit are rare in blue nevi. Benign and malignant blue nevi harbor frequent mutations in the Gαq class of G-protein α subunits, Gnaq and Gna11 proteins.