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Primary pleural thymoma: A mimic in thoracic pathology

Roberto Monaco ()
Antonietta D'Alterio ()
Raffaella Lucci ()
Oscar Nappi ()


We report a case of ectopic thymoma of the pleura with a growth pattern mimicking diffuse pleural mesothelioma. Diagnostic imaging showed that the pleural tumour encased the entire left lung. The specimen biopsied from the tumour was composed of lymphocytes and epithelial cells, consistent with the B1 type of thymoma. The surgical exploration of the anterosuperior mediastinum found no evidence of a thymic tumour. The thymoma was thought to originate from an ectopic thymic tissue in the pleura, as a lesion independent from the primary mediastinal thymoma, and it spreads along the pleura like a diffuse mesothelioma. Owing to their peculiar location and a variety of manifested histologic patterns, pleural thymomas may be confused with other neoplasms and may cause diagnostic problems clinically, radiologically, and morphologically. A combination of clinical information, histopathological appearance of the tumour, and immunohistochemical studies will often help to distinguish a primary pleural thymoma from other neoplasms. 


thymoma; ectopic thymus; pleura

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