Case Series: Postoperative recurrent secondary hyperparathyroidism caused by ectopic submandibular parathyroid: 3 cases report and literature review.

Postoperative recurrence for secondary hyperparathyroidism (SHPT) remains a clinical challenge. Ectopic parathyroid glands are a major cause of recurrence, and those located in the submandibular region are rare. This report retrospectively analyzes three patients on maintenance dialysis who developed recurrent elevation of parathyroid hormone (PTH) levels 3 to 37 months after parathyroidectomy (PTX) for SHPT. Neck ultrasound revealed no definite lesions; however, 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) single-photon emission computed tomography/computed tomography (SPECT/CT) fusion imaging showed abnormal radioactive tracer uptake in the submandibular region, suggestive of ectopic parathyroid glands. All three patients underwent a second or multiple surgeries, with complete excision of the submandibular masses. Postoperative pathology confirmed parathyroid tissue. After surgery, PTH levels returned to the normal range, and clinical symptoms improved markedly. Combined with a literature review, this article discusses the causes of recurrence after SHPT surgery, the anatomical basis of ectopic lesions in the submandibular region, and the localization diagnosis and treatment strategies for ectopic parathyroid glands, aiming to improve clinical awareness of such rare cases.