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

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.