Partial histological tumor regression in primary melanoma is a rather frequent event and has been reported in 10% to 35% of primary melanomas. Partial histological tumor regression is defined as an area within the tumor where melanoma cells have disappeared and are substituted by scarring and melanophages.1 Clinically, a skin-colored or depigmented area develops within the tumor. Regression is a clinical and dermoscopic criterion for the melanoma diagnosis. Partial tumor regression with scarring does not occur in benign melanocytic nevi.
Garbe C. Partial Histological Tumor Regression in Primary Melanoma as Protective Factor for Lymph Node Micrometastasis. JAMA Dermatol. 2015;151(12):1291-1292. doi:10.1001/jamadermatol.2015.2236