Brown tumors in nuclear medicine: a systematic review

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.

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.