A Hidden Parathyroid Adenoma Behind a Thyroid Autonomous Nodule Causing Multiple Brown Tumors: Advantages of Tomography Imaging Over Planar Imaging

Brown tumors in nuclear medicine: a systematic review

Brown tumors (BT) are abnormal bone-repair processes and a consequence of hyperparathyroidism. The diagnosis of these lytic lesions in nuclear medicine, while a challenge, is not so rare, because functional imaging is used both in the management of cancer and hyperparathyroidism. The main objective of this review is to summarize the knowledge and the evidence concerning BT and the different imaging modalities in nuclear medicine. A systematic review was performed in Embase, PubMed and Google Scholar from 2005 to 2022. We included articles describing BT in the following imaging modalities: [¹⁸F]-fluorodeoxyglucose PET/CT, [¹⁸F]-fluorocholine or [¹¹C]-fluorocholine PET/CT, [^99mTc]-Sestamibi scintigraphy, bone scan, [¹⁸F]-sodium fluoride PET/CT, [⁶⁸Ga]-FAPI PET/CT; [⁶⁸Ga]-DOTATATE PET/CT; [¹¹C]-methionine PET/CT. For each modality, appearance, avidity for radiotracer, available quantitative parameters and imaging evolution after parathyroidectomy were collected and analyzed. Fifty-two articles were included for a total of 392 BT lesions. If the diagnosis of BT is evoked on a known lesion, performing a [¹⁸F]-fluorocholine PET/CT imaging seems the most appropriate. In [¹⁸F]-fluorodeoxyglucose, [¹⁸F]-fluorocholine, [¹⁸F]-sodium fluoride PET/CT and bone scan, BT can mimic metastatic disease. BT uptakes appear reversible after parathyroidectomy, with a more or less rapid decrease depending on the imaging modality used.

FDG-anorectic parathyroid carcinoma with FDG-avid bone metastasis on PET/CT images

A 53-year-old man complained of aggravated left hip pain of more than 2 months. Whole-body (18)F-FDG PET/CT revealed only 1 hypermetabolic lesion in the left ilium. Histopathologic examination of the lesion suggested metastatic disease. Blood tests documented mildly elevated blood calcium and parathyroid hormone. Subsequent neck ultrasonography, contrast-enhanced CT, and dual-phase scintigraphy with (99m)Tc-MIBI showed a right parathyroid tumor, which was confirmed to be a parathyroid carcinoma postoperatively. We report a case of parathyroid carcinoma rarely encountered with a FDG-negative primary but a FDG-positive metastasis on PET/CT images.