2002 Volume 112 Issue 8 Pages 1115-1119
We report a 39-year-old female patient with a nodule on the right lower leg measuring 8mm in diameter. The nodule was asymptomatic, elastic hard in consistency, smoothly-surfaced, dome-like in shape, and brownish in color with a partial blackish hue and unclear border. Based on those features, we clinically suspected that it was malignant melamona. However, histologically, it was proved to be a variant of desmoplastic Spitz nevus, namely angiomatoid Spitz nevus, on the basis of the characteristic features of a predominance of solitary units or small nests of nevus cells which showed large plump-oval nuclei with prominent nucleoli and abundant cytoplasm. They were embedded in a fibrous stroma with many densely arranged, small blood vessels. The whole lesion was symmetrical in its architecture. Immunohistochemical studies showed the nevus cells were positive for S-100 protein and negative for HMB45. The tumor cells were positively stained in part for vascular endothelial growth factor and basic-fibroblast growth factor. It is thus considered that the nevus cells possibly release these growth factors, which may be related with the formation of prominent fibrous stroma and proliferation of small blood vessels.
