A neuroendocrine tumor within an anterior mediastinal mature teratoma: a case report

Mature teratomas are benign germ cell tumors. On rare occasions, they have been associated with somatic malignancies and are termed rare germ cell tumors with a somatic-type malignancy (GCTSM). Mature teratomas commonly comprise adenocarcinomas; only seven previous cases of mature teratomas with neuroendocrine tumors have been reported to date. Here, we report a patient with a neuroendocrine tumor whithin a mature teratoma.

A 26-year-old man visited our department complaining of chest tightness. Contrast-enhanced computed tomography (CT) scans showed a strongly enhanced lesion within a 10-cm encapsulated cystic lesion in the anterior mediastinum. Positron emission tomography (PET) scans showed no areas of significant ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) accumulation. He underwent complete tumor resection via the transsternal approach. Histopathological examination of the specimen indicated a neuroendocrine tumor contained within a mature teratoma.

In this case, a neuroendocrine tumor was contained within a mature teratoma. Our patient had no specific symptoms and his serum markers were within the normal range. Although PET is beneficial for diagnosing other GCTSM, it is not useful in detecting a neuroendocrine tumor. Therefore, the preoperative diagnosis of neuroendocrine tumors contained within mature teratomas remains challenging. However, GCTSM should be suspected in patients exhibiting CT findings of a mediastinal tumor, measuring ≥ 6 cm, in addition to characteristic GCTSM findings. Moreover, surgery should be performed carefully in such cases.