Diffuse-type tenosynovial giant cell tumor with t(1;17)(p13;p13) and trisomy 5.

Diffuse-type tenosynovial giant cell tumor (TSGCT) is a locally aggressive neoplasm that primarily affects the synovium and tendon sheath in young adults. Rearrangement of chromosome band 1p13 is now considered a characteristic genetic feature of TSGCT, with the most frequent chromosomal alteration t(1;2)(p13;q37). Here, we describe a unique cytogenetic finding of diffuse-type TSGCT arising in the ankle of an 18-year-old woman. Magnetic resonance imaging demonstrated an ill-defined juxta-articular mass with decreased signal intensity on both T1- and T2-weighted images. Contrast-enhanced T1-weighted images showed intense enhancement of the mass. Open complete resection was performed. Histologically, the tumor was composed of mononuclear cells admixed with multi-nucleated osteoclast-like giant cells, foam cells, siderophages and inflammatory cells. Cytogenetic analysis revealed a reciprocal translocation involving chromosomes 1 and 17, concomitant with a few other numerical and structural alterations. In addition, trisomy 5 as the sole anomaly was identified in two metaphase cells. To the best of our knowledge, this is the first report of this neoplasm with t(1;17)(p13;p13).