Cytopathological features of solitary fibrous tumor of the pleura: a study of 5 cases.

Solitary fibrous tumor is a rare lesion of serosal membranes. In a pleural location, it may be confused clinically with a localized mesothelioma or a peripheral lung tumor. A transthoracic needle aspiration can be done to obtain material for a diagnosis in these easily accessible tumors. In the literature, there are only sporadic reports of cytology of solitary fibrous tumor in pleural fluid or in material obtained by percutaneous fine-needle aspiration. We had the opportunity to study five such cases by cytology and biopsy and in four cases we could study the resected specimen as well. We want to emphasize the possibilities of approaching diagnosis by cytologic material. A more precise diagnosis can be made if immunohistochemistry can be applied on a cell block or a concomitant biopsy specimen. We shall discuss the differential diagnosis of these tumors on cytologic material and/or biopsy and the usefulness of the CD34 antibody.