Malignant pleural mesothelioma in a patient with pneumothorax: A cumbersome subtype both clinically and pathologically

Here, we report a case of malignant pleural mesothelioma (MPM) that was very difficult to diagnose. A 62‐year‐old woman with a surgical history of recurrent bilateral pneumothorax was admitted to our hospital with severe dysphagia. Computed tomography (CT) detected stenosis in the lower esophagus. Immunohistochemical examination of a biopsy sample from the stenotic region was suggestive of MPM. Chemotherapy was initiated, but the patient soon weakened and died. Autopsy revealed atypical cells, identical to those seen in the biopsy sample which had spread into the stenotic esophagus and entire thoracic cavity. Although neither pleural thickening/nodules nor asbestos bodies were observed, we finally diagnosed the tumor as a biphasic‐type MPM. We re‐examined previous surgical specimens of pneumothorax and acknowledged foci of bland mesothelial cell proliferation which had the same pathological findings as tumor cells at autopsy. The lack of asbestos exposure and pleural thickening, an initial manifestation of pneumothorax, and faint cytological atypia prevented an early diagnosis. In cases of recurrent pneumothorax in elderly patients, MPM should be included in the differential diagnosis.