Inverted type-A nevus is a benign melanocytic nevus variant characterized by deeply situated pigmented epithelioid or spindled melanocytes with type-A nevomelanocytic morphology, often occurring as part of a combined nevus. In contrast to the usual maturation pattern of conventional nevi, in which larger type-A nevus cells are more superficial and smaller type-B/type-C cells are deeper, inverted type-A nevus shows type-A melanocytes in the deeper dermis. Clinically, these lesions may show a blue-gray to blue-black focus of pigmentation and can raise concern for melanoma or blue nevus. Histologically, the deeply situated pigmented type-A melanocytes may mimic melanoma arising in a pre-existing nevus, but the absence of significant cytologic atypia, ulceration, destructive growth, and significant mitotic activity supports a benign diagnosis.
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