Ancient melanocytic nevus (AN) is an unusual but distinctive melanocytic neoplasm within the spectrum of simulators of malignant melanoma. This report describes 13 patients with AN where a long follow-up information was available. Histopathology is characterized by 2 populations of melanocytes, namely, one with large pleomorphic cells and the other with small melanocytes. A few mitotic figures may be present exceptionally. MIB-1 (Ki67) proliferation marker reveals an overall low nuclear labeling index. Additional important findings are stromal degenerative changes. AN must be especially differentiated from dermal melanoma arising in a nevus.