Innovative Approach of Endosonographic Radioactive Labeling of an Ectopic Parathyroid Adenoma by Technetium-99m Human Serum Albumin: A Case Report

Abstract

Primary hyperparathyroidism caused by parathyroid adenoma requires surgical resection. To confine the extent of surgery to the very minimum and to exclude an atypical adenoma location, preoperative imaging aims at identifying the suspicious gland. For this purpose, Technetium-99m (99mTc)-sestamibi scintigraphy and SPECT have become the international imaging standard, in inconclusive cases also with C-11 methionine and F-18 choline PET/CT. We present a case of surgery for an ectopic retroesophageal adenoma resected under gamma probe guidance after preoperative radioactive targeting. A 73-year-old patient, who was diagnosed with primary hyperparathyroidism, presented to our outpatient clinic. The patient was symptom-free, but during a routine check-up, parathormone levels of 127 pg/ml (normal range 15-65) were detected. Parathyroid MIBI scintigraphy, including SPECT/CT, failed to locate an adenoma. Therefore, a PET/MRI scan with 164 MBq F-18 choline was applied and a single parathyroid adenoma was detected in a very untypical retroesophageal and prevertebral position, respectively. Due to its esophageal proximity and to enable a very confined surgery, endosonography was performed and the adenoma was transesophageally injected with 75 MBq 99mTc-human serum albumin (HSA). The next day gamma probe-guided minimally invasive resection was performed without any intra- or postoperative complications. Minimally invasive resection of parathyroid adenomas should be the standard but may be difficult in deep collar and atypical locations. Marking the adenoma with a radioactive nanocolloid tracer for gamma probe-guided surgery can be considered an innovative approach to maintain minimal invasive therapy for ectopic adenomas.