SUN-062 - Thymoma as an Atypical Tumor in Multiple Endocrine Neoplasia Type 1: A Case Report

Introduction:
Multiple Endocrine Neoplasia Type 1 (MEN1) is a rare autosomal dominant hereditary disorder characterized by the predisposition to the development of neoplasia in multiple endocrine glands, primarily the parathyroids, enteropancreatic islets, and anterior pituitary, as well as non-endocrine neoplasms (1). While thymic neuroendocrine tumors are uncommon in MEN 1, thymomas, epithelial tumors of the thymus gland, are exceedingly rare, and relatively few cases have been reported in the literature.

Case:
A 22-year-old male with MEN1 presented to the clinic for surveillance follow-up. The patient initially presented with syncope at the age of 12 and was found to have a prolactin-secreting pituitary tumor. Germline genetic testing revealed a pathogenic mutation in the MEN1 gene
MEN1:p.Q261* (c.781C>T). To date, his manifestations of MEN1 include prolactinoma treated with cabergoline, hyperparathyroidism requiring 2 ½ gland parathyroidectomy, and a recent finding of a pancreatic neuroendocrine glucagonoma. Surveillance imaging revealed a new 3.2 x 1.8 x 2.3 cm anterior mediastinal mass. He underwent robotic assisted right mediastinal mass resection and en bloc thymectomy. The pathology revealed WHO Type B2 thymoma, pT1a, Masaoka stage II. At postoperative follow-up, the patient was doing well and will undergo serial surveillance imaging with chest CT.

Discussion:
Thymic tumors, including thymomas and thymic neuroendocrine tumors (NETs), are less common but significant components of MEN1. In association with MEN1, there are less than 10 reported cases of thymoma (2). The mechanism for the development of both NETs and thymomas is the somatic loss of heterozygosity at the MEN1 locus (3), suggesting they arise through a similar genetic mechanism as other MEN1-associated tumors. Thymic NETs in MEN1 have a well-documented poor prognosis, whereas thymoma generally has an excellent prognosis. This case aims to inform endocrinologists about a very rare non-endocrine manifestation of MEN1.


References:

1. Kamilaris CDC, Stratakis CA. Multiple Endocrine Neoplasia Type 1 (MEN1): An Update and the Significance of Early Genetic and Clinical Diagnosis. Front Endocrinol (Lausanne). 2019 Jun 11;10:339. doi: 10.3389/fendo.2019.00339. PMID: 31263451; PMCID: PMC6584804.
2. Gao Y, Li R, Wu L, Yang H, Mao J, Zhao W. Thymoma in multiple endocrine neoplasia type 1: a case report and systematic review. Endocrine. 2023 Nov;82(2):442-449. doi: 10.1007/s12020-023-03440-5. Epub 2023 Sep 5. PMID: 37668926.
3. Mandl A, Welch JM, Kapoor G, Parekh VI, Schrump DS, Ripley RT, Walter MF, Del Rivero J, Jha S, Simonds WF, Jensen RT, Weinstein LS, Blau JE, Agarwal SK. Two distinct classes of thymic tumors in patients with MEN1 show LOH at the MEN1 locus. Endocr Relat Cancer. 2021 Oct 4;28(11):L15-L19. doi: 10.1530/ERC-21-0226. PMID: 34515662; PMCID: PMC8558845.

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