¹⁸F-FDG PET findings of a parathyroid cancer with cortical skeletal demineralization

Parathyroid Carcinoma - A Malignant Cause of Metabolic Skeletal Super Scan on Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography

Excessive abnormal tracer uptake in active tracer avid organ(s) with the suppression of physiological background tracer distribution is termed as super scan. Herein, we present an ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT), where the metabolic pattern of skeletal super scan with coexistent parathyroid tumor was seen giving rise to the suspicion of primary hyperparathyroidism. It was subsequently diagnosed as a case of parathyroid carcinoma. Very high levels of serum parathormone in parathyroid carcinoma lead to accelerated bone turn over resulting in metabolic skeletal superscan in FDG-PET/CT which is seldom observed in parathyroid adenoma.

BROWN TUMORS SECONDARY TO PARATHYROID CARCINOMA MASQUERADING AS SKELETAL METASTASES ON 18F-FDG PET/CT: A CASE REPORT

Objective

Brown tumors develop as skeletal manifestations of hyperparathyroidism. Increased osteoclast activity leads to accumulation of highly active giant cells and to excess cortical bone resorption, producing fibrous cysts. Though most often reported in patients with parathyroid adenomas, brown tumors secondary to parathyroid carcinoma create a clinical dilemma. Increased signal uptake on 2-deoxy-2-(fluorine-18)fluoro-D-glucose positron emission tomography (¹⁸F-FDG PET)/computed tomography (CT) seen within brown tumors may be indistinguishable from bone metastases. We report a case of parathyroid carcinoma in a 38-year-old man presenting with osteolytic bone lesions on ¹⁸F-FDG PET/CT that were diagnosed as brown tumors by biopsy.

Methods

We describe the patient history, presentation, diagnostic studies, and treatment.

Results

We report a case of a 38-year-old man diagnosed with parathyroid carcinoma with associated hypercalcemia and elevated parathyroid hormone levels who had undergone 3 surgical resections for local recurrences and had persistent hypercalcemia. He was found to have multiple osteolytic lesions throughout his skeleton on ¹⁸F-FDG PET/CT imaging 2 months after diagnosis. Biopsy of a right scapula lesion confirmed a brown tumor.

Conclusion

The role of ¹⁸F-FDG PET/CT in management of parathyroid carcinoma has not been systematically evaluated. Skeletal manifestations of parathyroid carcinoma may be present in this imaging modality. Clinicians should consider the possibility of brown tumors in patients with parathyroid carcinoma who undergo ¹⁸F-FDG PET/CT imaging.

Brown Tumors Due to Primary Hyperparathyroidism in a Patient with Parathyroid Carcinoma Mimicking Skeletal Metastases on (18)F-FDG PET/CT

Parathyroid carcinoma only represents <1% of all cases of primary hyperparathyroidism (PHPT). Even rare, chronic PHPT may lead to excessive osteoclast activity, and the increased resorption leads to destruction of cortical bone and formation of fibrous cysts with deposits of hemosiderin-so-called brown tumors. These benign, osteolytic lesions may demonstrate FDG-avidity on (18)F-FDG PET/CT, and as such are misinterpreted as skeletal metastases. Regression of the lesions may occur following successful treatment. We present a case demonstrating the diagnostic work-up and follow-up of a patient with PHPT due to parathyroid carcinoma and with presence of brown tumors on (18)F-FDG PET/CT, visualizing the possible role of this imaging modality in the evaluation of treatment response in these patients.

Recurrent parathyroid carcinoma appearing as FDG negative but MIBI positive

A 44-year-old woman with recurrent parathyroid carcinoma (PTC) presents with moderately elevated parathyroid hormone and ionized calcium levels. Dual-phase Tc-MIBI SPECT study of the neck and chest demonstrated 2 new foci in keeping with neoplastic seeding. A restaging whole-body F-FDG PET/CT showed no evidence of FDG uptake in the region of the MIBI-positive foci or any evidence of distant metastases. The role of F-FDG PET/CT for imaging PTC is still somewhat limited because of the rarity of this disease. We present a case highlighting a potential pitfall for FDG PET in detecting PTC.

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.