malignant giant cell tumor of tendon sheath

Malignant giant cell tumor of the tendon sheaths and joints (malignant pigmented villonodular synovitis - malignant PVNS) is a rare lesion whose existence may be debatable.

Most cases of malignant PVNS are secondary, arising in patients in whom PVNS had been documented previously.

Important histologic features of malignancy are :
 (a) a nodular, solid infiltrative pattern of the lesion;
 (b) large, plump, round or oval cells with deep eosino philic cytoplasm and indistinct borders;
 (c) large nuclei with prominent nucleoli; and (d) necrotic areas.

Atypical mitoses were occasionally seen.

Evolution

 pulmonary metastasis
 metastasis to lymph nodes

The malignant nature of this lesion, the histologic architecture similar to that of PVNS, and the fibrohistiocytic appearance of the cells suggest that malignant PVNS is an entity.

References

 Malignant giant cell tumor of the tendon sheaths and joints (malignant pigmented villonodular synovitis). Bertoni F, Unni KK, Beabout JW, Sim FH. Am J Surg Pathol. 1997 Feb;21(2):153-63. PMID: 9042281