Malignant giant cell tumor of synovium (malignant pigmented villonodular synovitis) - A histopathologic and fluorescence in situ hybridization analysis of 2 cases with review of the literature

Context.-Pigmented villonodular synovitis (PVNS) is a well-recognized entit y that has the potential for extensive local destruction, even though it ra rely metastasizes. Rare reports of malignant forms are recorded in the lite rature. We observed 2 patients in whom examples of PVNS followed an aggress ive course with multiple recurrences, metastasis, or degeneration to an app earance resembling malignant fibrous histiocytoma. Objective.-We studied the occurrence and persistence of aneuploidy for chro mosomes 5 and 7 in 2 patients with clinically aggressive PVNS. Design-Fluorescence in situ hybridization was performed for the detection o f chromosomes 5 and 7 in the primary lesions, recurrences, and metastases i n 2 examples of PVNS. Results.-Fluorescence in situ hybridization demonstrated small but signific ant numbers of cells with trisomies for chromosomes 7 and/or 5 in both the primary and recurrent lesions of both patients. Conclusions.-The presence of consistent chromosomal trisomies (5 and 7) in both patients' examples of PVNS suggests a neoplastic nature for this lesio n. The persistence of these trisomies in the primary lesions, recurrences, and metastases supports a molecular link between the primaries, recurrences , and metastases despite changes in morphologic features. The presence of p ersistent trisomies in the recurrent and metastatic lesions supports the co ncept of malignant PVNS.