Soft Tissue Metastasis as Initial Manifestation of Pleural Malignant Mesothelioma

Abstract

Distant metastases of pleural malignant mesothelioma (MM) are infrequent. We report a case of MM that presented as a skeletal muscle metastasis. This type of presentation has not been previously reported. A 38-year-old male complained about a mass in his right forearm. The tumor showed the histologic pattern, immunohistochemical phenotype, and ultrastructural features of an MM. In the clinical work-up, the x-ray film and computed tomography scan demonstrated pleural effusion and diffuse pleural thickening in the right hemithorax. The pleural biopsy showed an epithelial MM. The patient died from local progression of the disease 6 months after the diagnosis. No other distant metastases were clinically evident. Our case shows the importance of including MM in the differential diagnosis of metastatic neoplasms in skeletal muscle and the usefulness of ancillary techniques in the diagnosis of mesothelial neoplasms.