Pleural biopsy: a reliable method for determining the diagnosis but not subtype in mesothelioma

Survival after tri-modality therapy with extrapleural pneumonectomy (EPP) and postoperative chemoradiotherapy is longer for patients with epithelial MPM versus mixed or sarcomatoid subtypes, leading some to decline aggressive therapy for patients with nonepithelial histology. However, pathologic diagnosis of malignant pleural mesothelioma (MPM) and subclassification into one of the three histologic subtypes (epithelial, mixed, sarcomatoid) can be challenging. Pleural biopsy has been proposed as the diagnostic gold standard. We investigated the accuracy of open pleural biopsy for diagnosis and subtype identification in MPM.

Patients with suspected MPM routinely undergo open pleural biopsy to establish diagnosis. Those diagnosed definitively by pleural biopsy or cytology are offered pleurectomy or EPP dependent on stage and cardiorespiratory status. We reviewed medical records for all patients undergoing EPP at our institution, comparing tissue and subtype diagnosis at initial diagnostic biopsy versus definitive resection.

Between 1988 and 2000, 305 of 332 consecutive patients undergoing EPP had MPM. One patient diagnosed with MPM at pleural biopsy was misclassified. Subtype analysis at pleural biopsy proved correct in 80% (226/282). Most patients (174/192) with epithelial subtype at final diagnosis were diagnosed correctly at pleural biopsy. However, 44% (45/103) with pathologic diagnosis of nonepithelial subtype at resection were initially misdiagnosed with the epithelial subtype. The sensitivity of pleural biopsy for epithelial MPM was 97% with a specificity of 56%.

Open pleural biopsy is accurate and should be considered the gold standard diagnostic method for MPM. It is less sensitive for determining histologic subclass, particularly with nonepithelial subtypes.