[Perihilar interstitial bleeding due to thoracic endometriosis].

A 47-year-old woman was admitted to our hospital for evaluation of an abnormal shadow in the left hilar region. A CT scan showed a non-enhancing mass between the lingula and left basal bronchus. On the twelfth hospital day, when her menstruation began, she suddenly expectorated a large amount of blood, and her chest X-ray film showed enlargement of the mass in the left hilum and an infiltrative shadow in the left lung field. We suspected pulmonary endometriosis because the hemoptysis was synchronized with the menstruation and because of her history of operations for polyps in the uterine cervix. Six days after the episode of hemoptysis, magnetic resonance (MR) imaging demonstrated a fluid-fluid level in the mass on T 2-weighted images. The abnormal signals spread along the interstitium into the lung parenchyma, therefore we made a diagnosis of hemorrhage in the perihilar interstitium due to endometriosis. MR images obtained 20 days and 48 days after the episode of hemoptysis showed changes of intensity in the mass similar to those of intracranial bleeding. This was a rare case of endometriosis in the perihilar interstitium and it shows the usefulness of MR imaging in making the diagnosis.