What are the future directions for research, including primary prevention?
Fully developed melanoma has cohesive clusters and single atypical melanocytes at the dermal-epidermal junction. Single melanocytes and clusters of melanocytes are dispersed through the full thickness of the epidermis. The invasive component forms an asymmetric lesion in the dermis, composed of atypical epithelioid and/or spindled melanocytes with an increased nuclear/cytoplasmic ratio; pleomorphic nuclei showing prominent nucleoli and mitoses, sometimes atypical; and abundant eosinophilic cytoplasm. There is no evidence of maturation from the superficial to deep component of the lesion. An associated inflammatory response, including tumor-infiltrating lymphocytes, is often present. Occasionally, angiolymphatic invasion and/or satellite nodules can be identified. Features of regression, including the presence of melanophages, lymphocytes, fibrosis, and vascular ectasia, with absence or degeneration of melanocytes in the papillary dermis, sometimes with no overlying intraepidermal compo
