Incidental thymic cyst in middle mediastinum during emergency coronary artery bypass grafting: case report

Abstract

Congenital thymic cyst is a rare mass and usually located in the anterior mediastinum and neck. Congenital thymic cyst in the middle mediastinum are extremely rare, with only three previously reported case. We herein describe the fourth case of a thymic cyst in the middle mediastinum.

Introduction

Thymic cysts are rare benign lesion of the mediastinum, comprising only 1% of all mediastinal cysts [1]. Occasionally, some have been found in the cervical portion. Thymic cysts are usually diagnosed incidentally during imaging of the chest or during operation for some other reason. Thymic cysts are more prevalent in young and middle-aged adults, and their origin could be congenital or acquired [2].

Case report

A 68-year-old woman, admitted with a history of severe chest pain and with diagnosis of acute myocardial infarction, was prepared for primary angioplasty. Due to perforation of left anterior descending artery and signs of tamponade, insertion of percutaneous pericardial drainage was done, and the patient was transferred to operation room for emergency coronary artery bypass grafting. During mediastinal exploration and pericardiotomy, a congenital thymic cyst (CTC) was incidentally found in the retro innominate vein area and extending to middle mediastinum. The cyst was well defined and encapsulated with a thin wall, without any sign of invasion to the surrounding tissue. The cyst was removed and sent for pathological examination. The surgical specimen was a unilocular cyst measuring 4 ×2.5 ×1.5 cm with a smooth yellow surface (Fig. 1). The cyst had a serous-like content. Histopathology showed a cyst measuring 2.5 cm in diameter, filled with gelatinous white material with a maximum wall thickness of 0.4 cm, compatible with unilocular thymic cyst (Fig. 2). No inflammatory cells, calcification, or hemorrhage was found in the cyst wall. The patient was discharged 1 week later.

Fig. 1.

Gross pathology of the thymic cyst

Fig. 2.

The cystic wall containing islands of thymic tissue

Discussion

Thymic cysts of the mediastinum are a rare finding, accounting for 1% of all the mediastinal masses. Thymic cysts are classified as unilocular and multilocular. Unilocular cysts are congenital and derived from remnants of the third branchial pouch derived thymopharyngeal duct and have thin-wall, filled with clear serous fluid. Multilocular cysts are acquired as the result of an inflammatory or neoplastic source. Thymic cysts involve males three times more often than females and are often found in children [3]. Most thymic cysts are asymptomatic, although symptoms could appear according to the size and location of the cyst. The most symptoms are chest pain, dyspnea, dysphagia, cough, and hoarseness. It must be noted that benign thymic cysts can also co-exist with malignant tumors [4]. Computed tomography is generally useful for preoperative diagnosis. The differential diagnosis includes thymomas, lymphomas, hemangiomas, and pericardial or bronchogenic cysts. The treatment of choice is complete excision of the cyst. In conclusion, thymic cysts in the retro brachiocephalic vein are extremely rare. Surgical resection results in definitive diagnosis.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Informed consent

Informed consent was obtained from all individual participants included in the study. Additional informed consent was obtained from all individual participants for whom identifying information is included in this study.

Ethical approval

All procedures performed in the studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standard.