Incidental finding of an ectopic retrosternal parathyroid adenoma in a patient operated on for controlled toxic multinodular goiter: a rare case report.

Background: Ectopic parathyroid adenomas are extremely rare in clinical practice and, therefore, represent a diagnostic challenge. Incidentally detected retrosternal adenomas are even rarer. Case presentation: We present the case of a 51-year-old female patient who presented with anterior neck swelling of 15 years' duration, associated with heat intolerance, fatigue, and palpitations over the preceding 2 years. She had no remarkable medical, surgical, or family history. On examination during her initial visit, her pulse rate was 96 beats/minute, and there was bilateral multinodular anterior neck swelling that moved with swallowing. Thyroid function tests showed a low thyroid-stimulating hormone level, for which she received antithyroid medications for 1 year and subsequently became euthyroid. During subtotal thyroidectomy, an approximately 5 × 3 × 3 cm oval, retrosternal, well-encapsulated mass with no continuity with the thyroid tissue was identified. The mass was removed without significant difficulty, and histopathological examination revealed colloid goiter in the thyroidectomy specimen and parathyroid adenoma in the ectopic tissue. Clinical discussion: Ectopic parathyroid adenomas represent a diagnostic challenge because of their rarity in clinical practice. Most reported cases of incidentally detected parathyroid adenomas involve glands located in their usual anatomical positions. However, our case is unique because the patient was normocalcemic, the adenoma was retrosternal and located in the superior mediastinum, and it was unusually large in size (5 × 3 × 3 cm). Conclusion: Preoperative normocalcemia does not preclude parathyroid disease. Any abnormally enlarged soft tissue identified in the vicinity of the thyroid gland during surgery should be thoroughly evaluated and, when appropriate, excised.