Analysis of chromosome 22q as an aid to the diagnosis of rhabdoid tumor - A case report

Malignant rhabdoid tumor is a highly aggressive tumor of childhood that may present as a soft-tissue primary tumor. We report a soft-tissue neoplasm t hat was polyphenotypic by immunohistochemical expression of epithelial, mes enchymal, and neural markers and did not meet the criteria for any of the u sual pediatric small round-cell tumors. The findings raised the diagnosis o f rhabdoid tumor, leading to testing for WT1 mRNA and protein expression, w hich were positive, as has been reported for renal rhabdoid tumor. This tum or had the typical clinical behavior of rhabdoid tumor with therapy resista nce and early tumor-related death. Multicolor spectral karyotyping of this neoplasm showed a balanced translocation between chromosomes 1 and 22 with breakpoints at 1p36 and 22q11-12. The latter region is commonly involved in rhabdoid tumor. This change was also identified by fluorescence in situ hy bridization. This case suggests that studies of chromosome 22 may be requir ed to distinguish rhabdoid tumor from other soft-tissue tumors.