Endocrine Abstracts

JOINT3821

Introduction: The combination of a parathyroid adenoma and thymoma is rare, with only few cases documented in the literature. This association may be explained by the shared embryological origin of the parathyroid glands and the thymus. We present here the case of a patient with primary hyperparathyroidism who was also found to have a thymoma in the anterior mediastinum.

Case presentation: A 60-year-old female patient was diagnosed with primary hyperparathyroidism based on hypercalcemia of 3.1 mmol/l, hypophosphatemia of 0.6 mmol/l, and inappropriate PTH level of 128 pg/ml. During the initial localization workup, a SPECT-CT scan showed an ectopic, hyperfunctional parathyroid gland located behind the manubrium of sternum. A chest CT scan revealed a calcified anterior mediastinal nodule in contact with the anterior surface of the ascending aorta, measuring 21 mm and a second lesion measuring 15 mm behind the manubrium sterni, corresponding to the hyperfixation area seen on the SPECT-CT. The patient underwent surgery with resection of the two masses. The histopathological report confirmed the diagnosis of thymoma (type AB1) and ectopic parathyroid adenoma.

Discussion: Primary hyperparathyroidism is a common endocrine disorder, with parathyroid adenomas accounting for 85% of cases. In about 10% of cases, the adenoma is ectopic due to abnormal embryological migration of the parathyroid glands. Despite their distinct primary functions, the parathyroid glands and thymus share a close relationship during organogenesis, as both are derived from the third branchial pouch. The association of a parathyroid adenoma with a thymoma is a rare clinical occurrence, with only a few cases documented in the literature. Patients may only present with the clinical signs and symptoms of primary hyperparathyroidism, making it difficult to suspect the presence of a thymoma. This association can be linked to familial syndromes, such as multiple endocrine neoplasia type 1.

Conclusion: Due to the close developmental link between the parathyroid and thymus glands, it is important to investigate the presence of thymic lesions when managing patients with primary hyperparathyroidism.