An Unusual Case of Desmoplastic Melanoma With Monster Cells Imitating an Atypical Fibroxanthoma

Numerous cells with very large and irregular nuclei ("monster" cells) have not hitherto been reported in desmoplastic melanoma (DM). Their prognostic significance in melanomas is a matter of debate, although some authors have associated them with more aggressive tumor behavior. We report a mixed DM on the scalp of an 88-year-old woman imitating an atypical fibroxanthoma. Tumor cells stained positive for SOX10, S100, and cyclin D1; BRAF mutation status was negative, and fluorescence in situ hybridization analysis showed copy number gains in 11q13 (cyclin D1) and 6p25 (RREB1), and loss in 6q23 (MYB). Cyclin D1 amplification is associated with poor prognosis in melanoma.