Malignant blue nevus: a case report and molecular analysis.

Malignant blue nevus is a rare melanocytic tumor that is described by some authors as a variant of malignant melanoma, whereas others regard it as a distinct entity. To our knowledge no molecular studies of this tumor have been performed, although the molecular pathogenesis of conventional melanomas has been extensively described. We present a case of malignant blue nevus that developed in a 15-cm congenital blue nevus on the back of a 41-year-old man. Subsequent regional lymph node and lung metastases developed within 1 and 29 months, respectively. We performed a molecular analysis for loss of heterozygosity on microdissected samples from the spectrum of benign to malignant blue nevus, using a panel of eight genes (MTS1, MXI1, CMM1, p53, NF1, L-myc hOGG1, and MCC), many of which are commonly associated with conventional melanomas. No loss of heterozygosity was detected, despite informativeness in seven genes. We suggest that malignant blue nevus may represent a distinct entity with a different molecular pathway to tumorigenesis than that of conventional melanomas.