[Lung metastases of epithelioid sarcoma revealed by bilateral spontaneous pneumothorax: a pathological diagnosis].

Spontaneous pneumothorax may be one of the presenting manifestation of metastatic epithelioid sarcoma even if imaging does not show evident metastatic nodules. We report the case of a 24-year-old man presenting a bilateral spontaneous pneumothorax in association with an epithelioid sarcoma developed in the right foot. CT-scan revealed bilateral microcystic lesions with no evidence of metastatic disease. A left thoracoscopy and a pleurodesis were performed. Persistent air leakage led to a thoracotomy during which lung biopsies were carried out. Histopathological examination of the pulmonary biopsies revealed rare millimetric nodules, composed of very atypical epithelioid cells, growing along alveolar walls reminiscent of a bronchiolo-alveolar carcinoma. However, these cells and primary neoplastic cells of the foot tumour were morphologically and immunohistochemically similar and the atypical pulmonary cells were TTF1 negative. All these constatations allowed a diagnosis of pulmonary metastases of the epithelioid sarcoma. This very unusual case underlines that sarcomatous metastases may be a clinical and pathological pitfall.