Solitary fibrous tumor: A pathological enigma and clinical dilemma

Solitary fibrous tumors are ubiquitous rare spindle cell neoplasms, most commonly arising from the pleura. Whilst now considered to be derived from mesenchymal cells, the histiogenesis has been the subject of debate. In 1931 Klemperer and Rabin first documented the occurrence of a distinctive localized pleural based tumour and proposed a submesothelial cell origin (1). Later, based on tissue culture experiments, Stout and Murray claimed derivation from mesothelial cells (2). This controversy is reflected in the variety of synonyms used for solitary fibrous tumors in the past including localized fibrous tumor, localized fibrous mesothelioma, solitary fibrous mesothelioma, fibrous mesothelioma, subserosal fibroma and submesothelial fibroma. With the advent of immunohistochemistry a fibroblastic origin, occasionally with myofibroblastic differentiation, is firmly established. This is further reinforced by the description of solitary fibrous tumors in extrathoracic sites devoid of mesothelial cells.