A survey of clusterin and fascin expression in sarcomas and spindle cell neoplasms: strong clusterin immunostaining is highly specific for follicular dendritic cell tumor

Clusterin, a glycoprotein implicated in many cellular functions including apoptosis, has recently been shown to be strongly expressed in follicular dendritic cell tumors, and to be absent or only weakly expressed in other dendritic cell tumors. Fascin has also been investigated as a potential marker of dendritic cell neoplasms. We evaluated staining for antibodies directed against these two antigens in 202 spindle cell tumors, including cases of follicular dendritic cell tumor (n=14), interdigitating dendritic cell tumor (n=7), leiomyosarcoma (n=17), inflammatory myofibroblastic tumor (n=13), inflammatory pseudotumor (n=2), spindle cell thymoma (n=17), synovial sarcoma (n=11), fibrosarcoma (n=14), liposarcoma (n=27), gastrointestinal stromal tumor (n=13), malignant fibrous histiocytoma (n=18), angiomatoid fibrous histiocytoma (n=4), angiosarcoma (n=10), malignant peripheral nerve sheath tumor (n=8), malignant melanoma (n=16), and spindle cell carcinoma (n=11). Among these spindle cell neoplasms, strong diffuse clusterin staining had an overall specificity of 93% and a sensitivity of 100% for follicular dendritic cell tumor. Clusterin staining was least reliable in distinguishing follicular dendritic cell tumor from spindle cell thymoma or malignant fibrous histiocytoma, but these are entities that usually can be distinguished by clinical and morphologic data. Rare cases of leiomyosarcoma, fibrosarcoma and angiosarcoma may show strong clusterin staining. Fascin staining was very nonspecific among spindle cell tumors and thus does not imply a dendritic cell lineage.