Clinical behavior of solitary fibrous tumors of the pleura. An immunohistochemical study.

Localized fibrous tumors of the pleura are uncommon, generally asymptomatic and usually have a benign behavior even if in a few cases a malignant variant can be observed. We report 11 cases of localized pleural neoplasms submitted to surgical resection during the period 1987-1996. The differentiation between the localized fibrous as well as the less frequent localized malignant mesothelioma has been researched employing cyto-histopathologic and immunohistochemical assays. For the purpose of identifying solitary fibrous tumors of pleura that will behave in malignant manner, we applied the more recent criteria of specific immunohistochemical stains, microvessel density and proliferation mdex. All solitary fibrous tumors resulted positive for Vimentin and negative for Cytokeratin. Among these forms, high cellularity and microvessel density, high expression of Ki 67 and CD31 and negativity of CD34 prognostic factors for a poor prognosis.