Spindle cell tumours of the pleura: a clinical, histological and comparative genomic hybridization analysis of 14 cases

We examined 14 spindle cell tumours of the pleura that were sent to a Mesothelioma Panel for re-evaluation after a primary suspicion of mesothelioma. The clinical, histological, immunohistochemical and CGH findings were investigated. Final diagnoses were eight sarcomatoid mesotheliomas (SM) and six non-mesotheliomas: two pulmonary sarcomatoid carcinomas, an epithelioid hemangioendothelioma, a malignant solitary fibrous tumour, a malignant pleural smooth muscle tumour and an extraskeletal osteosarcoma. Seven of the eight SM and two of the other six tumours presented with unilateral pleural effusion, dyspnoea, and chest pain, which are characteristic clinical findings in malignant mesothelioma. No single antibody used in the immunohistochemistry separated SM from other tumour types. The most frequently observed chromosomal losses in SM were 4q, 4p11-p13/p15, 6q and 13. Losses of 4p11-p13/p15 and 4q occurred in combination in four out of five SM with detectable chromosomal changes, but neither was found in any of the other tumours. Gain or high-level amplification of 5p was also common in SM. According to our results and literature, losses at 4p, 4q and 9p and gain at 5p are the chromosomal changes that best differentiate SM from pleural sarcomas and lung carcinomas. CGH analysis may help distinguish a cytokeratin-positive SM from a sarcomatoid carcinoma. Similarly, in the case of a cytokeratin-negative tumour, CGH analysis may disclose chromosomal changes characteristic of sarcomas or mesotheliomas.