Thymic Cyst with Rare Clinical Presentations: Report of Ten Cases over 13 Years

Thymic cysts are usually found in the anterior mediastinum. They comprise 1 to 4.8% of all the mediastinal cysts [1, 2]. Thymic cysts can also be found in the neck [1, 3]. Cervical thymic cysts often appear as a mass in the lateral part of the neck. Investigations have shown that about fifty percent of the cervical thymic cysts can extend into the mediastinum [4, 5]. Although mediastinal thymic cysts are rarely symptomatic, dyspnea, cough and chest pain have been reported in some cases [1, 5]. Computed tomography (CT) scan of the cervical lesions can be used to identify the cystic nature and determine the extension of lesions to the mediastinum[1, 6, 7]. Fine needle aspiration (FNA) under CT guidance, video-assisted thoracoscopic surgery (VATS) and thoracotomy are common procedures for the management of thymic cysts[1, 7, 8]. The purpose of this study was to report rare clinical features, diagnostic workup and surgical approaches in the management and outcome of patients with thymic cyst.

n this retrospective study, we reviewed the data of ten patients with thymic cyst in Respiratory Inflammatory Diseases Research Center, Razi Hospital of Rasht, Iran, between 2000 and 2013. We collected data on presenting symptoms, signs, imaging features including chest X-ray (CXR), CT scan and magnetic resonance imaging (MRI), surgical approaches and outcome. Patients underwent various surgical approaches, dependent on the location of the cyst and final diagnosis was established for each patient by pathological examination.

Eight patients were symptomatic; three had dyspnea, chest pain and pleural effusion, simultaneously. Symptoms of other patients are shown in table 1. The most common tool for diagnosis was CT. CT was used in all patients for the diagnosis of unilocular or multilocular, unilateral or bilateral, extension or invasion of cyst and also pleural effusion or pneumothorax (Table 2). One patient had a huge bilateral thymic cyst (Figure 1). One patient had hydropneumothorax and three patients had hydrothorax (Figure 2, 3, 6, 7). Surgical approaches for cyst excision were postero-lateral thoracotomy, sternotomy and antero-lateral thoracotomy (Table 3). Complications occurred in one patient as left phrenic nerve damage. Mortality was zero. Recurrence of the thymic cyst was not detected in any of patients during 4 years follow up by evaluation of CXR, CT-scan and MRI. Moreover, outcome of patients including previous symptoms and signs, working and social activities was good.

Thymic migration, during fetal development, may cause deposition of thymic remnants in the anterior mediastinum and neck [5]. Nowadays, it is believed that thymic cysts are either congenital or acquired [1, 5]. Investigations have shown that about fifty percent of the cervical thymic cysts extend into the mediastinum and most are found in the anterior mediastinum [1, 4]; however, the incidence rate of the mediastinal thymic cysts is low and comprises up to 4.8% of all mediastinal masses [1].