Postoperative radiotherapy for residual tumor of primary mediastinal carcinoid teratoma

Introduction

Teratomas are germ cell tumors commonly containing multiple cell types derived from different germ layers. Cystic teratoma is defined as a benign, well-differentiated cystic lesion, occurring in sequestered midline occasionally. Carcinoid tumor is considered as a neuroendocrine tumor with uncertain malignant potential. The main treatment of these tumors is complete surgical resection. However, it’s difficult if intrathoracic structures are intimately involved with the tumor (1). Thus, more approaches should be performed. Generally, salvage surgery is considered as the main treatment option for residual tumor. Radiotherapy is a good alternative option as well. However, there is little evidence for benefit from adjuvant chemotherapy.

In our case, a mediastinal carcinoid teratoma, which involved the aortic arch, was removed incompletely. To our knowledge, there were only 4 published articles to date reporting this rare tumor (2-5). Of these, residual diseases were not reported. Thus, we herein report a case of mediastinal carcinoid teratoma for this rare residual tumor with an effective radiation treatment at 2-year follow-up.

Case report

A 36-year-old woman had dry cough last for 2 months. Thoracic CT scan found an abnormal mass in the anterior mediastinum (Figure 1A,B). Tumor biomarkers (CEA, CA153, CA125, AFP and beta-hCG) were all within normal ranges. Patient was assessed to be suitable for operation (ECOG score =1). Thoracotomy was undergone with a sharp and blunt dissection. In the operation, a cystic mass, 12 cm × 8 cm ×5 cm, was found in the anterior mediastinum. The mass which involved the aortic arch was removed incompletely. The residual tumor was reported approximate 2 cm × 3 cm × 4 cm. Histological diagnosis was mature mediastinal cystic teratoma containing a carcinoid (Figure 2). Immunohistochemistry showed carcinoid cells were immuno-positive for CgA, Syn and NSE (Figure 3). Subsequently, adjuvant treatment with 6MV conventional intensity-modulated radiation therapy (IMRT) regimen was administrated on it for a total dose of 50 Gy at 2 Gy/d fraction in 25 fractions. At 2-year follow-up, the residual tumor was stable (Figure 1C,D). There is no evidence of disease progression found by routine examinations. Now the patient is kept under observation only with slight dry cough.

Figure 1. Thoracic CT revealed a primary mediastinal tumor before surgery (A, B), and a stable residual tumor (C, D) at 2-year follow-up.

Figure 2. Mature mediastinal cystic teratoma containing a carcinoid (H&E). A carcinoid was disposed by a cystic mass containing mature epithelial, muscular, vascular and nervous tissues (A, ×40). Moreover, carcinoid cells were presented to be monomorphic with uniform nuclei, conspicuous nucleoli and scanty cytoplasm (B, ×400).

Figure 3. Carcinoid cells were immuno-positive for CgA, Syn and NSE (×400). Abbreviations: CgA, chromogranin A; Syn, synaptophysin; NSE, neuron-specific enolase.

Discussion

Teratomas differentiate from various germ lines and could recapitulate any tissue of the body, including hair, teeth, skin, muscle, fat and so on. Mature teratoma is often considered as a benign lesion without metastatic potential. However, malignant transformation of mature teratoma is rarely occurred in 1-3% cases (6), including transformation to sarcoma (7), adenocarcinoma (8), squamous cell carcinoma (9) and carcinoid tumor. Malignant degeneration to carcinoid tumor is usually midline or paraxial, including ovary (10), testis (11), presacrum (12), retroperitoneum (13) and mediastinum (2-5).

Carcinoid tumor is generally considered to be a low-grade malignancy distributed throughout the body, including gastrointestinal tract (54.5%), lung and bronchus (30.1%), pancreas (2.3%), ovarian (1.2%), biliary (1.1%), head and neck (0.4%) and the other tissues (9.7%) (14). Generally, carcinoid tumor could display carcinoid syndrome including flushing, diarrhea and abdominal cramps. However, in this case, our patient didn’t have obvious carcinoid syndrome. It’s reported that an 82-year-old man who had a progressive carcinoid tumor rapidly died after admission (15). Thus, as a neuroendocrine tumor with potentially unfavorable outcome, carcinoid tumor requires more aggressive approach (16).

A carcinoid arised from a mature teratoma in mediastinum is extremely rare. Up to date, there are only 4 such cases described in world literatures (2-5). Of these, carcinoid tumors arised from slowly growing mediastinal teratomas. No residual tumor was reported. To our knowledge, it is the first case about this rare residual tumor at 2-year follow-up. In this case, our patient presented with an anterior mediastinal mass. Due to the anatomic location, we had removed it incompletely. In previous study, it’s usually chemoresistant (5). Second surgical procedure is recommended (17). However, radiotherapy is an effective approach as well (18). Thus, postoperative radiotherapy for residual tumor has been performed in this case subsequently. As experienced from our hospital, radiation treatment with 50 Gy is effective to achieve long-term local control. Now this patient is alive 2 years after surgery. In conclusion, we suggest that adjuvant radiotherapy with 50 Gy is an effective approach for residual tumor of mediastinal carcinoid teratoma.

Acknowledgements

Disclosure: The authors declare no conflict of interest.

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