A recent study among a panel of 13 expert dermatopathologists evaluating atypical Spitz tumors found low interobserver agreement in categorizing lesions as malignant versus nonmalignant.4 Of the 75 atypical Spitz tumor cases, there were 11 cases of malignant melanoma, as evidenced by histomorphologic appearance and disease progression. Although the majority of experts favored a melanoma diagnosis in 7 of 11 cases (67%), there were 4 cases (36%) in which the majority of experts did not favor a melanoma diagnosis. Of note, of the 2 cases with distant metastases, only 1 or 2 of the 13 experts favored a melanoma diagnosis. This highlights the ambiguity that still exists in the classification of atypical Spitz tumors. Misdiagnosis of a potentially malignant metastatic lesion as a phone number lookup indonesia benign atypical Spitz nevus by experienced dermatopathologists is concerning, and further investigation into ancillary tests that may help elucidate the clinical prognosis and classification of these lesions is warranted.
Ancillary studies including immunohistochemistry, CGH, and fluorescence in situ hybridization have shown promise in helping to distinguish melanocytic from nonmelanocytic lesions, but the sensitivity and specificity of the studies are not ideal. Immunohistochemical staining may be useful for the detection of mitoses to determine the proliferative activity of a lesion. The rate of staining with proliferation markers is generally lower in atypical Spitz nevi than in malignant melanomas. Increased expression of Ki-67, HMB-45, cyclin D1, and fatty acid synthase is most indicative of melanoma.5 Both fluorescence in situ hybridization and CGH are methods that can determine DNA copy number changes associated with certain types of melanocytic lesions. Most atypical Spitz nevi do not reveal genomic aberrations, in contrast to melanomas, in which more than 95% have shown multiple chromosomal aberrations. However, borderline lesions often show borderline features at the cytogenetic level, and the prognostic indication of these tests has not yet been clearly defined. For example, array-based CGH results from this case showed gains in chromosomes 17q and 1q, suggesting a partially transformed tumor without additional molecular testing supporting melanoma. As there are few reported cases of atypical Spitz nevi with chromosomal aberrations, the biological and prognostic significance of these findings is undetermined at this time. Although objective guidelines for optimal management of patients with atypical Spitz nevi cannot yet be recommended,6 complete excision with clear margins and careful follow-up are strongly recommended.