Atypical amplification of chromosome region 22q12 in melanoma: A case report.

Morphological, ultrastructural and immunohistochemical characteristics of clear cell sarcoma (CCS) of the soft tissue frequently overlap with those of malignant melanoma. Thus, the differential diagnosis between the two lesions represents an important diagnostic dilemma. However, a number of genetic factors can be used to differentiate the two tumors; in particular, the t(12;22)(q13;q12) chromosomal translocation is typical of CCS, resulting in fusion of the EWSR1 gene on chromosome 22q12 and the ATF1 gene on chromosome 12q13. The detection of this molecular alteration has proved useful in the differential diagnosis of the two lesions. The present study reports the case of a 71-year-old male patient with a suspicious lymph node mass. Immunohistochemical analysis of the lesion indicated a diagnosis of metastatic melanoma, however, cytogenetic analysis using fluorescence in situ hybridization was additionally performed to investigate the chromosomal rearrangements of the 22q12 region and completely exclude the possibility of CCS. The current case did not demonstrate the presence of the translocation, supporting the diagnosis of melanoma. However, a clear orange amplification signal was observed relative to an ~500-kb region adjacent to the EWSR1 gene in the centromeric direction of chromosome 22q12. To the best of our knowledge, this is the first description of a 22q12 chromosomal alteration in melanoma. Furthermore, despite the presence of numerous genes in this region, their amplification has not previously been associated with the pathogenesis of melanoma.