AB034. PS01.16: A case of thymic cyst with papillary proliferation of ciliated epithelium

Background: Thymic cysts account for about 5% of all mediastinal masses. The lumen wall is generally lined with single layer of ciliated epithelium. The papillary proliferation of ciliated epithelium in the lumen of thymic cyst is extremely rare. This is the first case report of thymic cyst with papillary proliferation of ciliated epithelium.

Methods: An 80-year-old female patient has been followed up by her family doctor for the cystic mass in the anterior mediastinum that was pointed out six years ago. She came to present a feeling of chest tightness, and referred to our department. The serial chest computed to mography showed gradual enlargement of the mass shadow. Magnetic resonance imaging showed septation in the cystic lesion. The border of the tumor was clear, and showed no invasion to the surrounding tissue.

Results: We performed thoracoscopic surgery as a diagnostic therapy. The tumor was well defined, and a tense cyst with serous contents and white floating substances. Macroscopic intraoperative findings suggested a diagnosis of a thymic cyst based on the finding the continuity between the tumor and thymus. Pathological diagnosis was a thymic cyst with involuted thymic tissue. The papillary proliferation of ciliated epithelium in the lumen of thymic cyst was identified, and any malignant finding was not recognized. The patient's postoperative course was uneventful and was discharged home on the 11th postoperative day.

Conclusions: Ciliated epithelium in the lumen of the thymic cyst were recognized as papillary proliferation. This is of unexplained origin, and need to be investigated further pathologically.

Keywords: Thymic cyst; papillary proliferation