A rare case of multiple endocrine neoplasia type 1 initially presenting as an asymptomatic, huge mediastinal mass: case report

Background Multiple endocrine neoplasia type 1 (MEN1) is a rare inherited syndrome that concurrently involves various endocrine glands. We report a rare case of MEN1 in a 43-year-old man whose first manifestation was an asymptomatic mediastinal mass. Case presentation A 13-cm-sized mediastinal mass was diagnosed as an atypical thymic carcinoid by computed tomography and percutaneous needle biopsy. In addition, hypercalcemia from a left inferior parathyroid hyperplasia, and a non-functioning gastric neuroendocrine tumor seen on esophagogastroduodenoscopy were found. Therefore, the patient was clinically diagnosed with MEN1 syndrome, and underwent surgical resection of thymic carcinoid tumor after pre-operative concurrent chemoradiation therapy to decrease tumor size and volume. Parathyroid lesion and gastric neuroendocrine tumor were also removed. Finally, a MEN1 gene mutation was observed in the patient and his 7-year-old son. Conclusion Despite its rare occurrence, thymic carcinoid tumor should be considered as a MEN1-associated tumor and necessitates screening of other endocrine glands. Thymic carcinoid tumor carries a poor prognosis in patients with MEN1, and thus it needs to be carefully monitored even after radical excision.