Desmoplastic melanoma: expression of epithelial-mesenchymal transition-related proteins.

Desmoplastic melanoma (DM) is a rare variant of melanoma. Most frequently, it seems as clinically ambiguous and histologically characterized by a poorly demarcated neoplasm composed of a proliferation of spindle melanocytes dispersed in a prominent collagenous stroma. It often represents a diagnostic challenge, delaying its detection. We analyzed the expression profile of 29 (28 "pure" and 1 "combined") DM. These data were compared with a series of 62 primary vertical growth phase nondesmoplastic melanomas (NDMs) using a set of proteins including melanocytic markers (S-100 protein and melan-A) and epithelial-mesenchymal transition (EMT)-related proteins (E-cadherin, N-cadherin, SPARC, WT1, and PKCα). The S-100 protein confirmed the melanocytic origin of the DM (positive in 96%). The significant positive expression of N-cadherin, SPARC, and WT1 in DM (61%, 82%, and 71%) compared with NDM (28%, 43%, and 47%; P < 0.05) and a lower expression of E-cadherin in DM (14%) compared with NDM (61%) support specific adhesive and migratory properties of DM tumor cells. The study was carried out with tissue microarrays that partly limited the study of the tumor sections. This study demonstrates, for the first time, a prominent expression of epithelial-mesenchymal transition-related proteins in DMs and tries to be one more step in refining its knowledge and leading to a better understanding of its biological and clinical behaviors.