Cushing Syndrome Secondary to A Thymic Carcinoid Tumor Due to Multiple Endocrine Neoplasia Type 1

Objective To present an Iranian patient with a nonclassic form of multiple endocrine neoplasia type 1 (MEN 1) who presented with ectopic Cushing syndrome (CS) secondary to a corticotropin (ACTH)-producing thymic neuroendocrine tumor (NET), recurrent renal stones, and a giant cell granuloma of the jaw due to primary hyperparathyroidism (PHPT) without involvement of the pituitary or pancreas. Methods Relevant imaging and hormonal evaluations were performed. The patient was operated on 2 occasions for a thymic NET and on 3 occasions for PHPT. DNA from a peripheral blood sample was extracted for sequencing of the MEN1 gene. Result Histopathologic evaluation of the thymic tumor removed during the first surgery showed an atypical carcinoid tumor with a Ki-67 labeling index of 5%. Evaluation after the second surgery revealed an invasive carcinoid tumor with a Ki-67 labeling index of 30%. Parathyroid pathology was suggestive of glandular hyperplasia. Menin gene sequencing revealed a novel frameshift mutation c.1642_1648dup in exon 10. Conclusion This case of MEN 1 is unusual because most thymic NETs in MEN 1 are nonfunctional, and secretion of ACTH or other ectopic hormones rarely occurs. In patients presenting with thymic NETs, the possibility of MEN 1 should be considered, especially in the presence of hyperparathyroidism. This case also demonstrates that the behavior of thymic NETs can change over time from slow-growing tumors to highly invasive neoplasia, and that ectopic ACTH can be produced by these tumors in the context of MEN 1. (Endocr Pract. 2011;17:e92-e96)