Melanoma Pathology

Excerpt

Melanoma is a type of skin cancer involving melanocytes—the pigment cells responsible for the skin's tan color that resurface to the topmost skin layer (see Image. Malignant Melanoma of the Skin). These cells provide an evolutionary benefit by protecting skin DNA from ultraviolet (UV) radiation and exposure. The accumulation of DNA mutations, most often secondary to UV light radiation from excessive sun exposure, contributes to the melanocyte's loss of division inhibition. A thorough understanding of the histopathological features of melanoma is crucial for comprehending the biology of the tumor, thereby leading to a more precise treatment decision.

Histologically, melanoma lesions are characterized by their architectural and cytological features. Architectural features include asymmetry, irregular borders, and variable coloration. Cytological features include cellular pleomorphism, nuclear atypia, presence or absence of ulceration, and mitotic activity. Immunohistochemical stains, such as S100, Melan-A, and human melanoma black-45 (HMB-45), aid in confirming melanocytic differentiation and distinguishing melanoma from other tumors. Breslow depth and Clark level are crucial histological prognostic indicators for melanoma.

Melanoma exhibits molecular heterogeneity, resulting in various subtypes with distinct clinical behaviors and therapeutic responses. The main subtypes include superficial spreading melanoma, nodular melanoma, lentigo maligna melanoma, and acral lentiginous melanoma, each characterized by unique clinical and histopathological features. See Image. Malignant Melanoma. Understanding these subtypes is essential for accurate diagnosis, prognostication, and treatment.