Ectopic right parietal pleural thymic carcinoma: a rare case and review of the literature

Abstract

Ectopic thymic carcinoma is extremely rare. We present a case of a 73-year-old male patient with ectopic right parietal pleural thymic carcinoma and performed a literature review. J Thorac Dis 2017;9(7):E609-E613 jtd.amegroups.com enhancement and a clear boundary adjacent to the ribs and intercostal tissue (Figure 1). An intrathoracic malignant tumor, most likely local malignant pleural mesothelioma or lung carcinoma with invasion into the parietal pleura, was suspected. CT images of the abdomen and skull showed no signs of lymph node enlargement or metastatic disease. An emission CT showed no signs of bone metastasis. Blood tests for tumor biomarkers were negative.The patient was scheduled for surgery. He underwent a video-assisted thoracoscopic surgery. A 7 cm × 4 cm × 3 cm tumor was found with a pedicle stemming from the anterior parietal pleura. It was tightly adhered to the right upper lung. No pleural effusion or nodules were found. There was no connection between the tumor and the mediastinum or the thymus. There was no obvious thymus tissue around the tumor. A totally extra-pleural tumor resection with partial right lung resection was performed. Fast frozen tissue specimen showed a poor differentiated squamous cell carcinoma. Hilar and mediastinal lymph nodes were dissected. Histological examination demonstrated infiltrative growth typical of carcinoma cells with a nestlike distribution that locally invaded the surface of the lung tissue but did not involve the subpleural tissue of the parietal pleura. The carcinoma cells were large and oval with a prominent nucleolus. A small amount of lymphocytes had also infiltrated among the carcinoma cells. Hyperplasia of collagen fibers existed between the cell nests. Immunohistochemical examination was positive for CD5, P63, and CK5/6, but negative for TIF-1, CD56, synaptophysin (Syn), mesothelial cell (MC), calretinin (CR), Wilm's tumor 1 protein (WT1), S-100, HMB-45, and Epstein-Barr virus RNA (EBER) (Figure 2). No lymph node metastases were found. These findings support a diagnosis of ectopic thymic squamous cell carcinoma. Cells that are CD5+ are specific for the diagnosis of primary thymic carcinoma (6). A final diagnosis of right parietal pleural ectopic thymic carcinoma was made.The patient was discharged on the 5 th postoperative day after an uneventful hospital course. Mediastinal radical radiotherapy (60 Gy) was performed postoperatively. The patient declined combined synchronous chemotherapy and thymectomy. After 17 months follow-up, the patient remained alive without any evidence of disease recurrence or metastasis. DiscussionThymic carcinomas are rare tumors (7) that usually occur in the anterior mediastinum. Rarely, however, ectopic thymic carcinoma can occur where the cancer is located outside of the mediastinum. Only 4 cases have been previously reported in the English literature. One case was a 49-year-old man who presented with cervical ectopic thymic squamous cell carcinoma with a microcarcinoma in his remnant mediastinal thymus (2). A...

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