Sensitivity and specificity of histological criteria in the diagnosis of conventional cutaneous melanoma

The efficacy of the histological criteria currently used in the diagnosis of melanoma is still to be defined. We performed a quantitative analysis of 72 conventional (non-Spitzoid, nondesmoplastic) melanomas and 73 conventional melanocytic naevi, used as controls, for 13 histological diagnostic parameters (dimension >6 mm, asymmetry, poor circumscription, irregular and confluent nests, single melanocytes predominating, absence of maturation, suprabasal melanocytes, asymmetrical melanin, melanin in deep cells, cytological atypia, mitoses, necrosis and dermal lymphocytic infiltrate). Differences in the distribution of selected parameters between the two groups were investigated by Fisher's exact test; for each parameter sensitivity and specificity were calculated. Results showed that all parameters, except poor circumscription, seemed to be significantly associated with melanoma (P<0.05). Cytological atypia, dermal lymphocytic infiltrate, asymmetry, dimension >6 mm and absence of maturation showed a high sensitivity (>90%); absence of maturation, mitoses, necrosis, asymmetrical melanin, suprabasal melanocytes and melanin in deep cells showed a high specificity (>90%); irregular-confluent nests and single melanocytes predominating were poorly sensitive and poorly specific. In melanomas <2 mm, two additional parameters were sensitive (>= 90%): suprabasal melanocytes and single melanocytes predominating. We conclude that not all parameters showed to have the same diagnostic value. Absence of maturation and, limited to melanomas <= 2 mm, suprabasal melanocytes were the most discriminating (sensitive and specific) histological features. Cytological atypia, dimension >6 mm, suprabasal melanocytes and mitoses were additional reliable diagnostic features, showing a relatively high sensitivity and a relatively high specificity. Other useful features were dermal lymphocytic infiltrate and asymmetry (sensitive) and necrosis, asymmetrical melanin and melanin in deep cells (specific).