Nevus associated malignant melanomas--diagnostic validation and prognosis

The diagnosis and prognosis of naevus-associated malignant melanomas are examined in the present study. For this purpose, 581 cases of primary malignant melanoma seen in the University Department of Dermatology, Berlin Steglitz, were histologically investigated for naevus association. A naevocytic association was proven in 135 (23%) of the malignant melanoma biopsies. Naevocytic malignant melanomas were found at a significantly higher rate (P less than 0.01) in patients under 50 years of age. The 5-year survival rate for naevocytic melanomas was not significantly different from that for other malignant melanoma types: around 80% in both groups. An immunohistological evaluation of the diagnosis of naevus-associated melanoma was also performed on the basis of specimens from 89 melanocytic lesions. The use of HMB-45 for diagnosis of melanocytic tumours made it possible to differentiate resting dermal naevus cells from malignant melanoma infiltrates in paraffin sections in the present study, thus simplifying the diagnosis of naevus-associated malignant melanomas. However, dysplastic naevi, junctional naevi and juvenile melanomas are also stained by HMB-45, which means that malignant melanomas associated with junctional melanocytic naevi still cannot be reliably identified even today.