Desmoplastic melanoma involving head and fingers: diagnostic challenges and clinical characteristics

Desmoplastic melanoma (DM) is considered a variant of melanoma, characterized by a paucicellular proliferation of malignant spindled melanocytes with an abundant collagenous or "desmoplastic" stroma and an intense inflammatory response. As DMs lack pigmentation, their appearances vary and can mimic many benign and malignant conditions, thus presenting a diagnostic challenge. Here, we are presenting one case involving the head and two cases involving fingers. One of our cases distinctively invade nerves and bones. We reviewed the literature for many similar cases. Most cases presented positive staining of S-100 and negative or focal positive staining of Melan-A and Melanoma. So far, the mechanisms of the rare entity have not been clearly recognized. Early accurate diagnosis and complete excision of this tumor is necessary. Some researchers considered BRAF-targeted therapy may be limited to a small number of patients with DM. Advanced DM may respond well to anti-PD-1 monotherapy.