Although thymic carcinoid tumor is recognized as a part of MEN1 syndrome but functioning thymic carcinoid tumor as the first presentation of the MEN1 seems to be very rare.
Our cases illustrate the importance of a high index of suspicion for early diagnosis and lifelong surveillance in MEN1, and the utility of genetic analysis in defining surveillance for MEN1-related thymic carcinoid.
In a series of 27 thymic epithelial tumors, including thymic carcinomas (n = 8), atypical thymomas (n = 5), thymomas (n = 13), and thymic carcinoid (n = 1), 7 (88%) thymic carcinomas and 1 (20%) atypical thymoma showed positive immunoreactivity for CD70, whereas CD70 was not detected in other tumors.
We, therefore, studied the presence of GHS receptor (GHS-R) messenger ribonucleic acid (RNA) in 38 human pituitary tumors of different cell types, 3 ectopic ACTH-secreting tumors, a pancreatic gastrinoma, 3 insulinomas, and a non-secreting thymic carcinoid as well as in 7 normal pituitary glands.
The pancreatic gastrinoma sample showed expression similar to that of normal pituitary tissue, whereas 3 insulinomas showed low level expression of the GHS-R gene; a nonsecreting thymic carcinoid tumor showed no detectable expression.