Smith et al. (1989) have reported a variant of Spitz's
nevus with histological atypical features. Despite local
lymph node metastases, further
metastases were not observed. They proposed the name "malignant
Spitz nevus" for this variant. A 2-year-old Japanese girl had a large nodule (27 x 17 mm) surrounded by an indurated
erythema over the Achilles tendon. Histologically, it proved to be a melanocytic lesion resembling spindle cell and epithelioid cell
nevus (Spitz's
nevus) with unusual features; the
tumor extended deep into the subcutis, and the mitotic figures deep into the
tumor, together with prominent lymphatic vessel invasion by melanocytes. Thus the
tumor was aptly termed "malignant
Spitz nevus". Flow cytometric analysis of the
DNA content revealed a diploid pattern. The child is well 5 years after a wide resection of the
tumor. The diploid pattern of the
DNA content as well as the good prognosis could support the idea that "malignant
Spitz nevus" fits within the spectrum of Spitz's
nevus.