A thymic cyst in the middle mediastinum: report of a case.
BACKGROUND
Thymic cysts are usually located in the neck or anterior mediastinal compartment. Thymic cysts arising in the middle mediastinum are extremely rare, with only 2 previously reported cases. We herein describe the third case of a thymic cyst in the middle mediastinum.


METHODS
A 41-year-old female was referred to our department because of an incidental mediastinal mass detected on chest X-ray. Computed tomography showed a well-defined 7 cm mass located in the retroinnominate vein area. Magnetic resonance imaging showed a cystic lesion without any soft tissue density in the circumference. The border of the tumor was clear, without any invasion and continuity with the surrounding tissue. We performed thoracoscopic surgery. After aspiration of the serous contents in an end-pouch, the tumor was removed from the thoracic cavity. A pathological examination showed a fibrotic cyst wall containing the thymic cyst, which diagnosed it as thymic cyst.


CONCLUSIONS
Thymic cysts in the middle mediastinum are extremely rare. A surgical resection provided the histological diagnosis of a thymic cyst in the present case.
Department of Thoracic Surgery, Tokyo Teishin Hospital, Tokyo, Japan.
Eiki
E
Mizutani
Kazuki
K
Nakahara
Shigeki
S
Miyanaga
Tomoharu
T
Yoshiya
Yukiko
Y
Kishida
Koichi
K
Tamura
D000328:Adult; D005260:Female; D006801:Humans; D033162:Incidental Findings; D008279:Magnetic Resonance Imaging; D008476:Mediastinal Cyst / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D011237:Predictive Value of Tests; D013396:Suction; D013906:Thoracoscopy; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome