Coincidence of Mature Cystic Teratoma and Serotonin-producing Neuroendocrine Tumor of the Ileum

Mature cystic teratomas are often found in gonadal sites, but are very rarely located extragonadally, for example, in retroperitoneum, mediastinum, central nervous system, lung, or liver. In the literature, only 10 cases of cystic teratoma originating from the diaphragm have been reported. Here, we report for the first time a metachronous occurrence of a benign mature cystic teratoma in the left diaphragm together with a serotonin-producing neuroendocrine tumor of the ileum. The 51-year-old, female patient received a partial resection of the ileum due to a neuroendocrine tumor (pT3N1M0) 4 years ago. Furthermore, she was operated for a benign cystadenoma of the right ovary 3 years ago. In her past medical history, she had an appendectomy in her childhood and a subtotal thyroidectomy 10 years ago. To our knowledge, this is the first report describing the metachronous occurrence of benign mature cystic teratoma in the diaphragm and a highly differentiated neuroendocrine tumor of the ileum. The possible coincidence of both diseases is discussed.