OBJECTIVEAnalyze the immunophenotype of the different cells in the various subtypes of giant cell tumor of tendon sheath (GCTS) and investigate the value of clusterin in pathological diagnosis and histogenesis of giant cell tumor of tendon sheath.

METHODSA total of 104 cases of GCTS from the surgical pathology files of Shanghai Jiaotong university affiliated the sixth people's hospital were identified. Immunohistochemistry (IHC) for clusterin, desmin, CD163, CD68, p63, p53, Ki-67 and CD35 was performed on all cases, using EnVision technique.

RESULTSAll cases of GCTS were researched, including 44 cases of localized type (L-GCTS), 32 cases of diffused type (D-GCTS), 26 cases of pigmented villonodular synovitis (PVNS) and 2 cases of malignant type. There was a slight female predominance in all these subtypes, and the male to female ratio was about 38:66. L-GCTS usually occured within the small joints (90.9%, 40/44), while D-GCTS, PVNS and M-GCTS commonly occured within the large weight-bearing joints [68.8% (22/32), 100% (26/26) and 2/2 respectively]. Of 74 cases with follow-up, the recurrence rates of L-GCTS, D-GCTS, PVNS and M-GCTS respectively were 30.3% (10/33), 30.4% (7/23), 18.8% (3/16) and 2/2. The different subtypes of GCTS had the same cell components, including the large synovial-like mononuclear cells, the small histiocytoid cells, foamy histiocytes cells, inflammatory cells, fibroblasts and the osteoclast-like multinucleated giant cells. There were obvious differences among immunophenotype of the various cell components in GCTS: the large synovial-like mononuclear cells were strong positive for clusterin, partly positive for desmin and Ki-67, and negative for CD163. The small histiocytoid cells were strong positive for CD163 but negative for clusterin and desmin. The osteoclast-like multinucleated giant cells were strong positive for CD68 but negative for clusterin, CD163 and desmin. Normal synoviocytes were strong positive for clusterin, partly positive for desmin. The number of the large synovial-like mononuclear cells that were positive for clusterin in D-GCTS were more than that in L-GCTS (P < 0.01) and PVNS (P < 0.05).

CONCLUSIONSGCTS was synovial tumors, not belonged to the category of fibrohistiocytic lesions. The true tumor cells may be the large synovial-like mononuclear cells, and the number of the cells in the D-GCTS was obviously more than that in L-GCTS and PVNS. This may be the reason that the biological behavior of D-GCTS was more aggressive, destructive and recurrent. Clusterin was an useful marker in pathological differential diagnosis of GCTS.