QUANTIFICATION OF VASCULARITY IN NODULAR MELANOMA AND SPITZS NEVUS

Spitz's nevi are acquired benign melanocytic skin tumors. Usually they are differentiated from nodular melanoma by clinical and histopatholo gical criteria. Since Spitz's nevi are one of the most common simulato rs of nodular melanomas their bizarre histopathology ma) cause diagnos tic confusion and make it difficult to differentiate these two melanoc ytic tumors, One of the histologic features shared by Spitz's nevus an d nodular melanoma is prominent vascularity. The ability of malignant melanoma to induce angiogenesis is well established whereas benign mel anocytic tumors do not have a prominent overall vascularity. The purpo se of this study was to find out whether the degree of vascularity of nodular melanomas differs significantly from that of benign Spitz's ne vi. In this study, the number of microvessels and the vessel area were determined in 23 Spitz's nevi and 16 nodular melanomas. The number of microvessels and the vessel area were determined on Ulex Europaeus ag glutinin I-stained sections by computer-assisted image analysis, Two m ethods of measurement were used, namely systematic and selective sampl ing, Measurement of the whole tumor specimen (systematic sampling) rev ealed a vessel count of 10.83/field (SD +/- 5.97) for Spitz's nevi whe reas nodular melanomas exhibited a significantly lower (p=0.04) vessel count of 6.44/field (SD +/- 3.85). This difference was even more pron ounced when the vessel area (Spitz's nevi: 17.85x10-4mm(2), SD +/- 10. 32; nodular melanomas: 7.88x10-4mm(2), SD +/- 5.23) was investigated ( p < 0.001). The difference in vessel area and vessel count was insigni ficant for areas exhibiting the greatest vascularity (selective sampli ng), Measurement of vessel count and vessel area lead us to conclude t hat Spitz's nevi have a significantly higher vascularity than do nodul ar melanomas. Our results thus indicate that angiogenesis in these pig mented lesions is not correlated with malignancy.