Desmoplastic melanoma (DM) is a rare and specific cytomorphologic variant in the cutaneous malignant melanoma spectrum. It is important to review its unique clinical characteristics and morphologic patterns as the experience of it in any one institution is low. Since the lesions are often amelanotic, their clinical appearance is variable mimicking scars, dermatofibromas, basal cell carcinomas, squamous cell carcinomas and other neoplams as well. Consequently, the initial biopsy is often delayed. In addition, histologic misdiagnosis is common. All these problems concur to delay proper surgical therapy of DM. Conventional histology and immuno-histochemistry are of the utmost importance for reaching the diagnosis of DM, and to assess the extension of the neoplasm, particularly its potential neurotropism. The neoplastic melanocytes may exhibit unusual poorly differentiated phenotypic characteristics. Desmoplasia is likely due to other cell lines including numerous Factor XIIIa-positive dermal dendrocytes and rare a-actin-positive myofibroblasts. CD45-positive lymphocytes and Mac 387-positive monocytes/macrophages are also clustered inside DM. The main differential diagnoses include sclerotic blue nevus, sclerosing Spitz melanocytoma, fibrosarcoma, schwannoma and other peripheral nerve sheath neoplasms. The prognosis of DM is comparatively better than that of conventional malignant melanoma of similar thickness. Prompt definitive surgical excision of DM with wide margins is the treatment of choice.
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