Brown tumors in nuclear medicine: a systematic review

Use of bone-SPECT/CT and Na[18F]F-PET/CT in hyperparathyroidism

Hyperparathyroidism disrupts the balance of physiological bone formation and resorption by upregulating osteoclast activity. This leads to hypercalcemia, resulting in osteoporosis and eventually the formation of "brown tumors." Currently used radiological and nuclear medicine imaging for primary hyperparathyroidism face challenges in accurately diagnosing bone-related complications. Molecular bone imaging techniques routinely consist of bone scintigraphy, with possible addition of bone-SPECT/CT. Recently, renewed interest has emerged in the use of Na[18F]F-PET/CT. Both applications are highly sensitive to in vivo osteoblast activity. However, the latter technique offers improved spatial resolution and sensitivity, as well as shorter incubation and faster scanning. This article summarizes current limitations and potential improvements in bone-SPECT/CT and Na[18F]F-PET/CT imaging in selected patients with hyperparathyroidism, compared to other relevant techniques and clinical parameters.

18F-Fluorocholine-Positron Emission Tomography/Computerized Tomography (FCH PET/CT) Imaging for Detecting Abnormal Parathyroid Glands: Indication, Practice, Interpretation and Diagnostic Performance

In patients with confirmed hyperparathyroidism (HPT) scheduled for surgical treatment, the preoperatory imaging permits to optimize the operatory protocol of parathyroidectomy (PTX), in particular by selecting those patients who can benefit from minimally invasive PTX (MIPTX). The MIPTX has the merit to shorten the operative time, incision length, and to reduce the operatory risks. With preoperative localization studies, the rate of PTX failure, in particular due to nonsuspected multiglandular or ectopic disease, has been profoundly decreased. The first cases of incidental localization of abnormal parathyroid glands (PTs) on FCH PET/CTs performed for another indication were reported more than one decade ago. Since then, significant amount of data from heterogeneous series of patients consistently confirmed better diagnostic performances of FCH PET/CT (sensitivity for detection of abnormal PT 97%, range 96%-98%) in comparison with other radiopharmaceuticals, ultrasonography or 4D-CeCT in localizing hyperfunctioning parathyroid glands (HFPTGs) in case of primary HPT. Utility of FCH PET/CT in case of renal HPT has been reported in fewer series. The article discusses and summarizes the bibliographic evidence on documented indications of FCH PET/CT in patients with HPT, its safety profile, the practice of FCH PET/CT and interpretation of FCH PET/CT findings, including potential interpretation pitfalls and tips to avoid them. Our real-world experience over 12 years reinforces published evidence supporting the use of FCH PET/CT as the first-line radionuclide imaging technique in patients with all types of HPT in whom surgery is an option.

Endocrinology application of molecular imaging: current role of PET/CT

BACKGROUND

In recent years, nuclear medicine imaging methods have proven to be of paramount importance in a wide variety of diseases, particularly in oncology, where they are crucial for assessing the extent of disease when conventional methods fall short. Moreover, nuclear imaging modalities are able to better characterize lesions using target agents related to specific pathways (e.g. glucose metabolism, cellular proliferation, amino acid transport, lipid metabolism, specific receptor ligands). The clinical presentation of endocrine diseases encompasses a broad spectrum of sign and symptoms. Moreover, endocrine tumors show varying degrees of aggressiveness from well differentiated and indolent to highly aggressive cancers, respectively.

RATIONALE

With the application of new medicinal radio-compounds and increasingly advanced tomographic imaging technology, the utility of Positron Emission Tomography/Computed Tomography (PET/CT) in the field of endocrine diseases is expanding.

AIM

This review aims to analyze and summarize the primary indications of PET/CT, providing a practical approach for clinicians. A comprehensive literature search on PubMed was conducted to provide an updated overview of the available evidence regarding the use of PET/CT in endocrinology. Within this review, we will discuss the applications of PET/CT, compare different radiopharmaceuticals and highlight the uptake mechanism, excluding neuroendocrine carcinomas from discussion.

CONCLUSIONS

PET/CT is a valuable tool in diagnosing and managing endocrine disorders due to its capacity to furnish both functional and anatomical information, facilitate early lesion detection, guide treatment decisions, and monitor treatment response. Its non-invasive nature and precision make it an integral component of modern endocrine healthcare. This review aims to provide physicians with a clear perspective on the role of PET/CT imaging, discussing its emerging opportunities and appropriateness of use in endocrinological diseases.

Complimentary Role of [18F]FDG and [18F]NaF-PET/CT in Evaluating Synchronous Thyroid Carcinoma and Parathyroid Adenoma with Brown Tumors

We herein present a patient initially suspected of multiple lytic skeletal metastasis of unknown primary on anatomical imaging. Metabolic imaging by [18F]-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) detected focal [18F]FDG uptake in the right thyroid nodule, mild [18F]FDG uptake in soft tissue lesion in the left inferior parathyroid region, and multiple nonavid osteolytic skeletal lesions. Fine-needle aspiration cytology of the right thyroid nodule showed papillary thyroid carcinoma (PTC). The patient had raised serum parathyroid hormone and serum calcium levels, suggesting parathyroid disease. [18F]-sodium fluoride (NaF)-PET/CT showed a metabolic superscan pattern of hyperparathyroidism with brown tumors rather than metastatic lytic skeletal lesions. Patient underwent total thyroidectomy and bilateral central compartment clearance, along with soft tissue lesion resection in the left inferior parathyroid region. Finally, histopathology confirmed PTC classical variant with no aggressive histology features (pT1N0) for thyroid nodule and parathyroid adenoma for soft tissue lesion in the left inferior parathyroid region. The findings of the [18F]FDG and [18F]NaF-PET/CT imaging were helpful for making a final diagnosis of synchronous thyroid cancer and parathyroid adenoma, which in turn guided the appropriate treatment strategy.

Brown Tumors: The Hidden Face of Primary and Renal Hyperparathyroidism Amid Real-Life Settings

Brown tumors, an exceptional bone complication of severe primary (PHP) or renal (secondary) hyperparathyroidism (RHP), are caused by long-standing, elevated parathormone (PTH)-induced osteoclast activation causing multinucleated giant cell conglomerates with hemosiderin deposits in addition to the local production of cytokines and growth factors. We aim to present an adult case series including two females displaying this complication as part of a multidisciplinary complex panel in high PTH-related ailments. The approach was different since they had distinct medical backgrounds and posed a wide area of challenges amid real-life settings, namely, a 38-year-old lady with PHP and long-term uncontrolled hypercalcemia (with a history of pregnancy-associated PHP, the removal of a cystic jaw tumor, as well as a family and personal positive diagnosis of polycystic kidney disease, probably a PHP-jaw tumor syndrome), as well as, a 26-year-old woman with congenital single kidney and chronic renal disease-associated RHP who was poorly controlled under dialysis and developed severe anemia and episodes of metabolic acidosis (including one presentation that required emergency hemodialysis and was complicated with convulsive seizures, followed by resuscitated respiratory arrest). Both subjects displayed a severe picture of PHP/RHP with PTH levels of >1000 pg/mL and >2000 pg/mL and elevated serum bone turnover markers. Additionally, they had multiple brown tumors at the level of the ribs and pelvis (asymptomatically) and the spine, skull, and pelvis (complicated with a spontaneous cervical fracture). As an endocrine approach, the control of the underlying parathyroid disease was provided via surgery in PHP (for the postparathyroidectomy hungry bone syndrome) via medical intervention (with vitamin D analogs) in RHP. Additionally, in this case, since the diagnosis was not clear, a multidisciplinary decision to perform a biopsy was taken (which proved inconclusive), and the resection of the skull tumor to confirm the histological traits. This series highlights the importance of addressing the entire multidisciplinary panel of co-morbidities for a better outcome in patients with PHP/RHP-related brown tumors. However, in the instance of real-life medicine, poor compliance and reduced adherence to recommendations might impair the overall health status. Thus, sometimes, a direct approach at the level of cystic lesion is taken into consideration; this stands for a narrow frame of decision, and it is a matter of personalized decision. As seen here, brown tumors represent the hidden face of PHP/RHP, primarily the complex and severe forms, and awareness is essential even in the modern era.

Multiple brown tumors: a bone complication due to long-term untreated pseudohypoparathyroidism

Bone lytic lesions are a possible complication of pseudohypoparathyroidism type 1B, in undertreated adult patients. Whole body [18F] F-fluorocholine PET/CT is a useful imaging tool to assess brown tumor progression in this context. We describe the case of a 33-year-old woman, referred for the diagnostic evaluation of lytic bone lesions of the lower limbs, in the context of asymptomatic pseudohypoparathyroidism. She had been treated with alfacalcidol and calcium during her childhood. Treatment was discontinued at the age of 18 years old because of the lack of symptoms. A femur biopsy revealed a lesion rich in giant cells, without malignancy, consistent with a brown tumor. Laboratory tests showed a parathyroid level at 1387 pg/ml (14-50). Whole-body Fluorocholine PET/CT revealed hypermetabolism of bone lesions. The final diagnosis was brown tumors related to hyperparathyroidism complicating an untreated pseudohypoparathyroidism. Genetic testing confirmed PHP type 1B. Pseudohypoparathyroidism with radiographic evidence of hyperparathyroid bone disease, is a very rare condition due to parathyroid hormone resistance in target organs, i.e., kidney resistance, but with conserved bone cell sensitivity. It has been reported in only a few cases of pseudohypoparathyroidism type Ib. Long-term vitamin D treatment was required to correct bone hyperparathyroidism. With this rationale, the patient was treated with calcium, alfacalcidol, and cholecalciferol. One-year follow-up showed complete resolution of pain, improvement in serum calcium, and regression of bone lesions on [18F]F-fluorocholine PET/CT. This case illustrates the usefulness of [18F]F-fluorocholine PET/CT for the imaging of brown tumors in pseudohypoparathyroidism type 1B, and emphasizes the importance of calcium and vitamin D treatment in adult patients, to avoid the deleterious effects of high parathyroid hormone on skeletal integrity.

Hypopituitarism due to a Large Osteoclastoma Arising from the Sphenoid Bone Invading the Pituitary Fossa in a Patient with Parathyroid Carcinoma

Background

Parathyroid carcinoma accounts for <1% of cases of primary hyperparathyroidism (PHPT). This rare condition may present with severe hypercalcemia and bone complications such as osteoclastomas and pathologic fractures. Here, we present a rare condition of panhypopituitarism resulting from an osteoclastoma in the sphenoid bone that invaded the pituitary fossa due to parathyroid carcinoma. Case Report. A 47-year-old woman previously diagnosed with PHPT underwent a parathyroidectomy 6 years earlier, with histological examination indicating a parathyroid adenoma. After surgery, she continued to exhibit high serum parathyroid hormone (PTH) and calcium levels, with the development of bone pain and spontaneous fractures. Imaging exams showed a large osteoclastoma of the sphenoid bone, invading the pituitary fossa, causing hypopituitarism. A new parathyroidectomy was performed, with histological confirmation of parathyroid carcinoma and regression of the osteoclastoma.

Conclusion

This case illustrates an unusual presentation of parathyroid carcinoma, in which an osteoclastoma of the sphenoid bone caused hypopituitarism.

Increased Uptake of Brown Tumor in 99m Tc-HYNIC-TOC Scintigraphy Mimicking Postoperative Recurrence of Tumor-Induced Osteomalacia

ABSTRACT

A 61-year-old man underwent a resection of tumor in the left tibia that caused osteomalacia 11 years ago. Postoperative bone pain and fatigue symptoms were briefly relieved but then recurred. To identify potential recurrent tumors, 99m Tc-HYNIC-TOC scintigraphy was performed. Images revealed an osteolytic lesion in the right tibia with increased uptake. The lesion was subsequently resected, which pathologically proved a brown tumor. Symptoms of bone pain and weakness caused by osteomalacia did not relieve 4 months after the operation. Here, we present a rare case of brown tumor with high activity on 99m Tc-HYNIC-TOC SPECT/CT, mimicking a culprit tumor of osteomalacia.