Ectopic thymoma presenting as a giant intrathoracic tumor: A case report
© Kitada et al; licensee BioMed Central Ltd. 2011
Received: 27 February 2011
Accepted: 28 June 2011
Published: 28 June 2011
Ectopic thymoma rarely presents as an intrathoracic tumor. We report a case of ectopic thymoma presenting as a giant right intrathoracic tumor that was treated with resection. The patient was a 50-year-old Japanese woman who presented with the chief complaint of chest pain. Detailed examination revealed a solid tumor measuring 15 × 10 × 8 cm in diameter, with a clear border. The Imaging findings suggested a solitary fibrous tumor, and surgery was performed. At surgery, the tumor was found to beadherent to the diaphragm, mediastinal pleura, and lower lobe of the lung, although it could be dissected with relative ease and was removed. Pathological diagnosis indicated a type B1 tumor with no capsular invasion according to the World Health Organization classification, and a diagnosis of Masaoka stage I thymoma was made. No continuity with the normal thymus tissue was seen, and the thymoma was considered to be derived from ectopic thymic tissue in the pleura.
Thymomas usually manifest in the anterior-superior mediastinum, and ectopic thymomas account for only 4% of all thymomas. Among ectopic thymoma, intrathoracic tumors of pleural origin are rather rare. We report, herein, a patient with a giant intrathoracic tumor that was discovered during a clinical workup to determine the cause of chest pain in the patient. The tumor was diagnosed as a thymoma that was difficult to differentiate from solitary fibrous tumor (SFT) by diagnostic imaging.
Thymomas are tumors developing mainly in the thymus, are located in the anterior mediastinum, with 96% of the tumors occurring in the anterior or anterosuperior mediastinum, and only 4% being ectopic tumors [1, 2]. Ectopic thymomas have been described in the neck , middle mediastinum [4, 5] posterior mediastinum, lung , and pleura [7, 8], few reports have described giant intrathoracic tumors. Thymomas are generally asymptomatic, but symptoms such as chest pain and respiratory discomfort can be caused by compression of the surrounding organs due to growth of the tumor. Symptoms such as superior vena cava syndrome can also be coused by tumor invasion of the surrounding tissues, myasthenia gravis, pure red cell apalasia, hypogammaglobulinemia. These symptoms/complications can lead to the discovery of the tumor. In addition, some patients show multiple lung metastases or pleural dissemination arising from recurrence or metastasis. The intrathoracic tumor in the present patient was discovered during the course of a clinical workup for chest pain, caused by compression of the surrounding organs. The patient also showed restricted impairment of pulmonary function due to the pressure on normal lung tissue, and surgical removal of the thymoma as quickly as possible was therefore considered necessary.
Definitive diagnosis is needed before surgical removal of a thymoma is planned. The differential diagnosed for giant intrathoracic tumors include SFTs, tumors of pleural origin, such as malignant pleural mesothelioma or sarcoma, chest wall tumors, and metastatic tumors. In our patient, SFT was initially suspected on the basis of the MRI findings, including the shape, signal status under various weightings, and the presence of numerous linear non-signals that were considered to indicate flow voids within the lesion. It was considered that percutaneous needle biopsy would yield a definitive diagnosis, but this procedure was not performed considering the risk of tumor cell dissemination and bleeding from the tumor. Hemorrhagic shock induced by spontaneous rupture of a giant thymoma has been reported , and caution is warranted when considering biopsy.
Informed consent was obtained from the patient for publication of this case report and of the accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
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