A study of tumor progression: The precursor lesions of superficial spreading and nodular melanoma

摘要: Six evident lesional steps of tumor progression form the neoplastic system that affects human epidermal melanocyte: 1) common acquired melanocytic nevus; 2) a nevus with lentiginous hyperplasia, i.e., aberrant differentiation; 3) differentiation and nuclear atypia, dysplasia; 4) radial growth phase primary melanoma; 5) vertical 6) metastatic melanoma. The is viewed as focal proliferation melanocytes, destined in most instances to follow programmed pathway leads disappearance nevus. If not followed, characteristic lesions result, such are regarded formal histogenetic precursors Such developmental flaw termed differentiation, resultant precursor lesion designated dysplasia. vast majority nevi showing dysplasia terminal do progress melanoma develop via lesion, however, precursor. When melanomas develop, they focally within itself does inexorable expansion population cells space time. Rather, melanomas, exception nodular melanoma, also evolve stepwise fashion. first step, phase, characterized by net enlargement at its periphery, along radii an imperfect circle. Tumors this stage development show pattern epidermis distinctive invasion papillary dermis. associated metastasis, it hypothesized tumors have competence for metastasis. For acquire metastasis must next step progression—the phase. This appearance new forming preexisting perpendicular directional As rule, grow expansile fashion, balloon expands: metastases. It postulated those give rise metastasis; last described paper thought be paradigm neoplasia, from model sequence generic applicable general presented. These selective structurally normal (a benign tumor); abnormal hyperplasia (aberrant differentiation); random cytologic atypia atypia); cancer without cancer.