CD-34 and keratin expression distinguishes solitary fibrous tumor (fibrous mesothelioma) of pleura from desmoplastic mesothelioma.

Solitary fibrous tumors (SFTs) often involve the pleura and also may encompass the peritoneum and nonserosal sites. On occasion SFTs mimics other neoplasms, including desmoplastic mesothelioma. CD-34, initially characterized as a hematopoietic progenitor cell antigen, recently has been identified in a small number of SFTs. Based on this observation, we compared the keratin, vimentin, and CD-34 expression of 19 SFTs and eight desmoplastic mesotheliomas. Fifteen of 19 SFTs (78.9%) expressed CD-34, whereas keratin expression was absent in all SFTs. In contrast, none of the desmoplastic mesotheliomas expressed CD-34 and keratin expression was found in seven of eight (87.5%). Vimentin expression was noted in 18 of 19 SFTs and in seven of eight desmoplastic mesotheliomas. We conclude that CD-34 expression distinguishes SFT from desmoplastic mesothelioma. Additionally, the results of our study support the idea that SFT is not derived from or related to conventional mesothelium.