MDM2 dual-color in situ hybridization (DISH) aids the diagnosis of intimal sarcomas.

Intimal sarcoma is a rare malignant mesenchymal tumor arising from the intima of the great vessels and the heart, and is associated with poor outcomes. As clinico-radiological findings and pathological features are often non-specific, the diagnosis of intimal sarcoma is challenging. Recently, MDM2 amplification was reported to be a characteristic genetic event in this tumor. In the present study, we examined MDM2 status by immunohistochemistry, and by fluorescence and dual-color in situ hybridization (FISH and DISH) using intimal sarcoma (10 tumors), angiosarcoma (5), pulmonary sarcomatoid carcinoma (p-SC) (14) and chronic pulmonary thrombosis (CPT) (3) to investigate MDM2 amplification for the diagnosis of intimal sarcoma. MDM2 and CDK4 were immunopositive in all 10 intimal sarcoma tumors, and high-level amplification of MDM2 was detected in eight tumors by both FISH and DISH. The other two tumors had polysomy of chromosome 12 and overexpression of p53 protein. Although MDM2 aberrations were observed in three p-SCs (two with amplification and one with polysomy), angiosarcomas and CPTs lacked MDM2 amplification. Furthermore, there was high concordance between FISH and DISH. In conclusion, we found that MDM2 amplification strongly supports the diagnosis of intimal sarcoma, and MDM2 DISH was a concordant method and an acceptable alternative to FISH. As MDM2 amplification and p53 overexpression were mutually exclusive, disruption of the MDM2-p53 pathway may be an essential genetic event for this malignant tumor.