A case of atypical parathyroid adenoma

Abstract

Atypical parathyroid adenoma (APA) is a rare condition that is considered to be a borderline condition between adenoma and cancer. We herein report a case of APA. A 61-year-old man was referred to our department for a preoperative evaluation of lung cancer. Positron emission tomography-computed tomography showed an abnormal accumulation in the dorsal right lobe of the thyroid gland. Based on various examinations, the patient was suspected to have primary hyperparathyroidism due to the presence of adenoma and therefore underwent adenoma resection. The mass was resected, although it adhered to the surrounding tissues, such as the thyroid gland and the right recurrent nerve. The postoperative pathological diagnosis was APA, and the tumor cells were exposed on the resected surface, thus resulting in a positive surgical margin. The postoperative serum calcium levels thereafter normalized. The intact PTH level initially normalized one month after surgery, however, it later rose again, and remained above the upper limit of normal. A careful follow-up is needed, although no recurrence has been reported to date. When a parathyroid tumor adheres to the surrounding tissues during resection, the possibility of APA is suspected, and the surrounding tissue should therefore be removed a far as possible.