ESTIMATION OF THE VOLUME-WEIGHTED MEAN NUCLEAR VOLUME DISCRIMINATES SPITZS NEVI FROM NODULAR MALIGNANT MELANOMAS

BACKGROUND: Spitz's nevi are benign melanocytic skin tumors that are u sually differentiated from nodular malignant melanomas by histopatholo gic criteria. Often, however, the architectural pattern and cytologic features of Spitz's nevi and nodular melanomas are similar. Hence, Spi tz's nevi may be confused with nodular malignant melanomas at the hist opathologic level. EXPERIMENTAL DESIGN: The determination of volume-we ighted mean nuclear volume (($) over bar V-v) uses a technique that pe rmits an unbiased and efficient estimation of nuclear volumes in tissu es. In this study, ($) over bar V-v was determined in 13 Spitz's nevi and 14 nodular malignant melanomas to investigate whether this stereol ogic approach may be of use in the differentiation of these two tumors . ($) over bar V-v was determined by computer-assisted image analysis (IBAS 20, Kontron, Germany) on Feulgen-stained sections using stereolo gic estimation of the ($) over bar V-v. RESULTS: The ($) over bar V-v (+/- SD) of Spitz's nevi was 491.6 mu m(3) (SD +/- 175.1), whereas nod ular malignant melanomas exhibit a significantly higher (p < 0.001) ($ ) over bar V-v of 775.2 mu m(3) (SD +/- 205.4). This difference was ev en more pronounced when the deeper portions of the lesions (Spitz's ne vi: 443.1 mu m(3), SD +/- 142.4; nodular malignant melanomas: 864.1, S D +/- 169.6) were investigated. In addition, we found that in relation to the depth of the lesions the mean ($) over bar V-v decreased in Sp itz's nevi, whereas it increased in nodular melanomas. CONCLUSIONS: We found that (i) nodular malignant melanomas reveal a larger ($) over b ar V-v than Spitz's nevi in general, and (ii) in contrast to malignant melanomas, the ($) over bar V-v of nevomelanocytes in Spitz's nevi de creases in the deeper portions of the dermis. Thus, ($) over bar V-v m ay be regarded as a helpful tool for the differential diagnosis of Spi tz's nevi and nodular malignant melanomas.