Acral Lentiginous Melanoma
During the radial growth phase of acral lentiginous melanoma, the epidermis is hyperplastic and shows atypical melanocytes along dermo-epidermal junction. In established lesions, there is marked acanthosis with elongation of rete ridges. The atypical melanocytes have pleomorphic hyperchromatic nuclei, prominent nucleoli, and show frequent mitoses. Both in-situ and invasive component usually show spindle morphology. Some acral melanomas have superficial spreading in-situ component or show nodular features in invasive tumor. This tumor was present on the heel of an elderly male. The tumor invaded subcutaneous fat (Clark Level 5) and had spindle morphology (see next 6 images).