Malignant Giant Cell Tumor of Synovium (Malignant Pigmented Villonodular Synovitis)

Abstract

Abstract Context.—Pigmented villonodular synovitis (PVNS) is a well-recognized entity that has the potential for extensive local destruction, even though it rarely metastasizes. Rare reports of malignant forms are recorded in the literature. We observed 2 patients in whom examples of PVNS followed an aggressive course with multiple recurrences, metastasis, or degeneration to an appearance resembling malignant fibrous histiocytoma. Objective.—We studied the occurrence and persistence of aneuploidy for chromosomes 5 and 7 in 2 patients with clinically aggressive PVNS. Design.—Fluorescence in situ hybridization was performed for the detection of chromosomes 5 and 7 in the primary lesions, recurrences, and metastases in 2 examples of PVNS. Results.—Fluorescence in situ hybridization demonstrated small but significant 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 lesion. 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 persistent trisomies in the recurrent and metastatic lesions supports the concept of malignant PVNS.