Desmoplastic melanoma: an updated immunohistochemical analysis of 40 cases with a proposal for an additional panel of stains for diagnosis

Desmoplastic melanoma ( DM ) is histologically characterized by a proliferation of spindle melanocytes dispersed in a collagenous stroma that can be mistaken for a variety of neoplasms. The purpose of this study was to analyze 40 cases of DM with a comprehensive panel of immunohistochemical markers ( KBA .62, p16, Ezrin, WT ‐1, MITF ‐1, SOX ‐10, CD117 , SOX ‐2, nestin, PNL2 , p75, MART ‐1, gp100 and S100p) to obtain a more complete understanding of the potential use of these antibodies in the diagnosis of DM . We found that all cases of DM expressed p16, WT ‐1, SOX ‐10, nestin and S100p and 95% of cases expressed p75. There was variable expression with Ezrin, SOX ‐2, KBA .62, MART ‐1 and HMB ‐45. Most DMs did not express MITF ‐1, PNL2 and CD117 . Conditions that may enter in the histologic differential diagnosis of DM , including dermal scars, fibromatosis and dermatofibromas were also studied. Nearly all control cases also stained positive for p16 but were negative for WT1 , SOX10 , nestin, p75 and S‐100p, as well as for most of the other markers tested. We conclude that a panel of S‐100p, WT1 , SOX10 , p75 and nestin may constitute the optimal panel with the most sensitive and specific combination of immunostain available for the diagnosis of DM .