Malignant melanoma with desmoplasia and neurotropism

Desmoplastic (DMM) and neurotropic (NMM) malignant melanoma are two variants of the vertical growth phase of malignant melanoma. Both lesions commonly present clinically as firm nodules that are often mistaken for fibromas. Histologically, they are associated with a pleomorphic spindle cell population of cells that widely infiltrate the dermis. An accompanying fibrosis is present. DMM usually lies beneath a lentiginous proliferation of a typical melanocytes, whereas NMM may arise without obvious epidermal involvement. Because the lesions infiltrate widely, adequate therapy results only when complete extirpation is performed. Otherwise, there may be recurrence. Recurrent lesions act more aggressively.