874 Solitary Fibrous Tumours of the Pleura: Immunohistochemistry

Abstract

Abstract Aim To evaluate immunohistopathology markers of solitary fibrous tumours of the pleura (SFTP), including markers of benign and malignant variants. Method Retrospective review of immunohistopathology reports on 4 patients diagnosed with SFTP between January-October 2020 at the Golden Jubilee National Hospital. Data was collated on markers tested or detected. Benign and malignant cases were compared. A literature review was conducted to summarise the current evidence. Results Ki-67, Anti-bcl-2, CD99, STAT6, Desmin, AE1/3, Calretinin and S100 were tested in 100% (4/4) cases. CD34, EMA and CD117 were tested in 75% (3/4). Betacatenin and Vimentin were tested in 25% (1/4). Of those tested, Ki-67 was present in 100% (4/4), Anti-bcl-2 and CD99 in 75% (3/4), STAT6 in 50% (2/4), Desmin in 25% (1/4), AE1/3 in 25% (1/4), Calretinin in 25% (1/4), S100 in 0% (0/4), CD34 in 67% (2/3), EMA in 0% (0/3), CD117 in 0% (0/3), Betacatenin in 100% (1/1) and Vimentin in 100% (1/1). One out of 4 cases were malignant based on clinical presentation. Of the markers tested in all cases, Desmin was only detected in the malignant case, AE1/3 and Calretinin only in the benign cases, and the other markers in both benign and malignant cases. Anti-bcl-2 and Ki-67 intensity did not correlate with tumour diameter or malignant potential. Immunohistopathology could not confirm SFTP diagnosis in 50% (2/4) cases; it could not determine malignant potential or SFTP-subtype in 100% (4/4) cases. Conclusions A better understanding of SFTP immunohistopathology is needed for investigating SFTP, including benign and malignant tumour variants.