Abstract
A 17-year-old male consulted a doctor with a chief complaint of chest discomfort. He was diagnosed with left pneumothorax and a chest drain was inserted. As the air leak did not stop, he was transferred to our hospital to undergo an operation. We performed video-assisted thoracic surgery the next day. We found the air leak point at the top of the lung and resected that part with a surgical stapler. We also detected a mass or tumor-like lesion which was covered with mediastinal pleura. We thought that it was abnormal because the mass was clearly swelling from part of the left lobe. We resected part of the left lobe for diagnosis. The mass and left lobe were connected with no clear boundaries. The pathological diagnosis after the operation was thymic hyperplasia as it showed a homogeneous thymic structure with no neoplasm and a tumor-like appearance. Thymic hyperplasia with a localized tumor-like appearance is relatively rare, and so we present it including a literature review.
