p16INK4A(CDKN2A) Gene Deletion Is a Frequent Genetic Event in Synovial Sarcomas

We assessed the frequency of genomic deletion of p16INK4A (CDKN2A) in synovial sarcomas (SSs) and its possible association with immunoexpression of p16 and cyclin D1 and the Ki-67 proliferation index using dual-color fluorescence in situ hybridization (FISH) on tissue microarray sections of 41 histologically and molecularly confirmed SSs. A heterozygous p16INK4A gene deletion was identified in 28 (74%) of 38 cases, with 25 (89%) of them showing abnormal p16 protein expression (20 negative and 5 heterogeneous). Of 25 cases, 19 (76%) exhibiting increased cyclin D1expression also demonstrated heterozygous p16INK4A deletion. No significant association was observed between p16INK4A deletion and Ki-67 proliferation index, tumor grade, or histologic subtype. Our results demonstrate that p16INK4A (CDKN2A) gene deletion is a frequent genetic event in SS.