Neuroendocrine tumors may occur in the setting of MEN1 syndrome. Among these a, probably underestimated, prevalence of well-differentiated neuroendocrine thymic carcinoma (carcinoid), a neoplasm characterized by a very aggressive behavior, has been described. We report the characterization of the seven Italian cases in which this association occurred among a series of 221 MEN1 patients (41 sporadic and 180 familial cases) (prevalence 3.1%). All the patients were male and 6 out of 7 (85%) were heavy smokers. No associated hormonal hyper-secretion was detected. First diagnosis was between the second and the fifth decade. Familial clusters were present in 3/7 (42.8%). No genotype-phenotype correlation was found. All the seven cases were associated with hyperparathyroidism. In one patient prophylactic thymectomy revealed a small nodular lesion suggestive of a thymic carcinoid providing evidence that preventive thymectomy might prevent further growth of an occult thymic carcinoid.

These findings confirm that thymic carcinoids are associated with a very high lethality, with a near-total prevalence in smoker males. Therefore prophylactic thymectomy should be considered at neck surgery for primary hyperparathyroidism in MEN1 male patients, especially for smokers, and, due to the frequent familial clusters distribution of this pathology, in subjects with affected relatives presenting this feature. Thus we recommend screening every patient affected with a neuroendocrine thymic neoplasm for MEN1 syndrome.