Activation of nevi in patients with malignant melanoma.

Activation of melanocytic nevi from patients with malignant melanoma is documented microscopically. Features of activation include marked junctional activity, lack of lateral margination of junctional melanocytic activity, and--to a lesser degree--increased pigment production, inflammation, mitotic activity, and cytologic atypia. The changes are most pronounced in nevi from the same lymph drainage region as the malignant melanoma, suggesting a local activating factor. The presence of marked junctional activity in these lesions and the occurrence of these changes in nevi of patients with clinical Stage I malignant melanomas provide evidence that these lesions do not represent metastases.