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

Approach to the Patient With Parathyroid Carcinoma

Parathyroid carcinoma (PC) is usually associated with severe symptomatic primary hyperparathyroidism (PHPT) and accounts for less than 1% of all cases of PHPT and approximately 0.005% of all cancers. PC most commonly occurs as a sporadic disease and somatic CDC73 mutations can be detected in up to 80% of cases. Approximately 30% of patients harbor a germline mutation of the CDC73 gene. Preoperative diagnosis of PC is difficult because no disease-specific markers are available, and PC should be suspected in patients with severe hypercalcemia and end-organ complications. The diagnosis is based on the evidence of invasive tumor growth at histology and/or metastases. En bloc resection of the tumor, together with the ipsilateral thyroid lobe and adjacent structures, should be performed by an experienced surgeon when PC is suspected. This surgical approach reduces the risk of recurrence and metastasis and offers the highest chance of cure. Nonetheless, PC has a recurrence rate of 40% to 60% and, if feasible, multiple surgical procedures should be performed. When surgery is no longer an option, medical treatment is aimed to reduce hypercalcemia and target organ complications. Targeted agents have been effectively used in a few cases. We describe herein a patient with severe PHPT due to PC and provide a systematic diagnostic and treatment approach. A thorough review of the medical history, a typical clinical and biochemical phenotype and, in some cases, the revision of the histological examination provide the clues for the diagnosis of PC.

Brown Tumour in Chronic Kidney Disease: Revisiting an Old Disease with a New Perspective

Osteitis fibrosa cystica (OFC) and Brown Tumours are two related but distinct types of bone lesions that result from the overactivity of osteoclasts and are most often associated with chronic kidney disease (CKD). Despite their potential consequences, these conditions are poorly understood because of their rare prevalence and variability in their clinical manifestation. Canonically, OFC and Brown Tumours are caused by secondary hyperparathyroidism in CKD. Recent literature showed that multiple factors, such as hyperactivation of the renin-angiotensin-aldosterone system and chronic inflammation, may also contribute to the occurrence of these diseases through osteoclast activation. Moreover, hotspot KRAS mutations were identified in these lesions, placing them in the spectrum of RAS-MAPK-driven neoplasms, which were until recently thought to be reactive lesions. Some risk factors contributed to the occurrence of OFC and Brown Tumours, such as age, gender, comorbidities, and certain medications. The diagnosis of OFC and Brown Tumours includes clinical symptoms involving chronic bone pain and laboratory findings of hyperparathyroidism. In radiological imaging, the X-ray and Computed tomography (CT) scan could show lytic or multi-lobular cystic alterations. Histologically, both lesions are characterized by clustered osteoclasts in a fibrotic hemorrhagic background. Based on the latest understanding of the mechanism of OFC, this review elaborates on the manifestation, diagnosis, and available therapies that can be leveraged to prevent the occurrence of OFC and Brown Tumours.

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.

Brown Tumors Secondary to Tertiary Hyperparathyroidism Masquerading as Lytic or Sclerotic Skeletal Metastases on Preoperative/Postoperative 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography: A Case Report

Tertiary hyperparathyroidism (TH) is a rare condition that develops from secondary hyperparathyroidism in cases when the secretion becomes autonomous. Brown tumors (BTs) are rare skeletal lesions of hyperparathyroidism that may mimic cancer metastasis. We report a case of a patient who was diagnosed with TH with multiple BTs which mimics osteolytic/osteoblastic metastases that were evaluated with two fluorodeoxyglucose positron emission tomography scans with an interval of 23 months in the preoperative and postoperative period.

A Case of Brown Tumor on 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT

ABSTRACT

A 50-year-old man presented with right chest pain and persistent increased parathyroid hormone after parathyroidectomy for parathyroid carcinoma. 68Ga-DOTATATE PET/CT and 18F-FDG PET/CT were performed consecutively for restaging to determine subsequent treatment strategy. An osteolytic lesion on the right sixth rib showed increased uptake on both 68Ga-DOTATATE and 18F-FDG PET/CT. Subsequent biopsy confirmed it to be a brown tumor.

A patient with multiple brown tumors due to secondary hyperparathyroidism: A case report

Brown tumor is an uncommon non-neoplastic radiolucent bone lesion due to a rapid bone loss replaced by haemorrhage and reparative granulation tissue. It is a manifestation of hyperparathyroidism related to the high level of parathyroid hormone and represents a problem linked to the adherence to therapy. We present a case of a 44 years-old Caucasian female with hemodialysis-dependent chronic kidney disease in poor sanitary condition with CT evidence of innumerable and widespread bone tumors. At first, we considered these bone lesions strongly suspicious for metastasis, so we recommended an oncological consultation and laboratory studies, that showed a secondary hyperparathyroidism with elevated serum parathormone level of 923 pg/mL (normal range: 10-70 pg/mL). According to our experience, in case of radiological evidence of multiple bone lesions, a correct medical history is mandatory. When the patient has a history of chronic kidney disease and dialysis and high blood levels of parathyroid hormone are present, secondary hyperparathyroidism should always be considered in the differential diagnosis.