Molecular genetics of syndromic and non-syndromic forms of parathyroid carcinoma

Familial states of primary hyperparathyroidism: an update

BACKGROUND

Familial primary hyperparathyroidism (PHPT) includes syndromic and non-syndromic disorders. The former are characterized by the occurrence of PHPT in association with extra-parathyroid manifestations and includes multiple endocrine neoplasia (MEN) types 1, 2, and 4 syndromes, and hyperparathyroidism-jaw tumor (HPT-JT). The latter consists of familial hypocalciuric hypercalcemia (FHH) types 1, 2 and 3, neonatal severe primary hyperparathyroidism (NSHPT), and familial isolated primary hyperparathyroidism (FIHP). The familial forms of PHPT show different levels of PHPT penetrance, developing earlier and with multiglandular involvement compared to sporadic counterpart. All these diseases exhibit Mendelian inheritance patterns, and for most of them, the genes responsible have been identified. DNA testing for predisposing mutations is helpful in index cases or in individuals with a high suspicion of the disease. Early recognition of hereditary disorders of PHPT is of great importance for the best clinical and surgical approach. Genetic testing is useful in routine clinical practice because it will also involve appropriate screening for extra-parathyroidal manifestations related to the syndrome as well as the identification of asymptomatic carriers of the mutation.

PURPOSE

The aim of the review is to discuss the current knowledge on the clinical and genetic profile of these disorders along with the importance of genetic testing in clinical practice.

Insights into Hyperparathyroidism-Jaw Tumour Syndrome: From Endocrine Acumen to the Spectrum of CDC73 Gene and Parafibromin-Deficient Tumours

A total of 1 out of 10 patients with primary hyperparathyroidism (PHP) presents an underlying genetic form, such as multiple endocrine neoplasia types 1, 2A, etc., as well as hyperparathyroidism-jaw tumour syndrome (HJT). We aimed to summarise the recent data, thus raising more awareness regarding HJT, from the clinical perspective of PHP in association with the challenges and pitfalls of CDC73 genetic testing and parafibromin staining. This narrative review included a sample-focused analysis from the past decade according to a PubMed search. We identified 17 original human studies (≥4 patients per article). The mean age at disease onset was between 20.8 and 39.5 years, while the largest study found that 71% of patients had HJT recognised before the age of 30. Males and females seemed to be equally affected, in contrast with sporadic PHP. PHP represented the central manifestation of HJT, occurring as the first manifestation in up to 85% of HJT cases. A biochemistry panel found a mean serum calcium level above the level of 12 mg/dL in PHP. PTH was elevated in HJT as well, with average values of at least 236.6 pg/mL. The most frequent pathological type in PHP was a parathyroid adenoma, but the incidence of a parathyroid carcinoma was much higher than in non-HJT cases (15% of all parathyroid tumours), with the diagnosis being established between the age of 15 and 37.5. In some families up to 85% of carriers suffered from a parathyroid carcinoma thus indicating that certain CDC73 pathogenic variants may harbour a higher risk. An important issue in HJT was represented by the parafibromin profile in the parathyroid tumours since in HJT both parathyroid adenomas and carcinomas might display a deficient immunoreactivity. Another frequent manifestation in HJT was ossifying fibromas of the jaw (affecting 5.4% to 50% of patients; the largest study found a prevalence of 15.4%). HJT was associated with a wide variety of kidney lesion (mostly: kidney cysts, with a prevalence of up to 75%, and renal tumours involved in 19% of patients). The risk of uterine lesions seemed increased in HJT, especially with concern to leiomyomas, adenofibromas, and adenomyosis. The underlying pathogenic mechanisms and the involvement of CDC73 pathogenic variants and parafibromin expression are yet to be explored. Currently, the heterogeneous expression of parafibromin status and, the wide spectrum of CDC73 mutations including the variety of clinical presentations in HJT, make it difficult to predict the phenotype based on the genotype. The central role of HJT-PHP is, however, the main clinical element, while the elevated risk of parathyroid carcinoma requires a special awareness.

Is there a role for liquid biopsy in the surveillance of parathyroid carcinoma?

BACKGROUND

Parathyroid carcinoma is a rare malignancy with high recurrence rates. Liquid biopsy is a stratifying tool in disease recurrence/progression in other malignant processes. This study sought to assess the feasibility and application of liquid biopsy in parathyroid carcinoma and its impact on surveillance.

METHODS

Retrospective review of a prospectively maintained database of adults treated for parathyroid carcinoma at a tertiary care center (2017-2023). Demographics, clinical characteristics, and laboratory variables were collected. Circulating cell-free deoxyribonucleic acid enrichment and circulating tumor cell enumeration were obtained from serial blood samples.

RESULTS

A total of 25 patients were identified-64% were male patients, with a median age of 56 years (interquartile range 45-63). Fifty blood samples were collected postoperatively. At first, circulating tumor cell enumeration, 56% (14/25) of patients had no evidence of disease, and 32% (8/25) had distant metastasis. Median follow-up was 53 months (interquartile range 23-107). At the last follow-up, 40% (10/25) of patients were found to have distant metastasis. Serial circulating tumor cell enumeration was performed in 52% of patients, median highest circulating tumor cell was (interquartile range 1-22). Circulating cell-free deoxyribonucleic acid was assessed in 64% of patients (16/25). There was no difference in circulating tumor cells or circulating cell-free deoxyribonucleic acid between those with distant metastasis and those without distant metastasis. The most common mutation identified was TP53, present in 88% of circulating cell-free deoxyribonucleic acid samples with a mutation. Circulating cell-free deoxyribonucleic acid and parathyroid hormone levels were not found to have any association (r = -0.27, P = .39), but parathyroid hormone and circulating tumor cell had a linear relationship (r = 0.76, P < .001).

CONCLUSION

Liquid biopsy appears to be a feasible tool in parathyroid carcinoma surveillance. The relationship between circulating cell-free deoxyribonucleic acid and parathyroid hormone levels remains unclear, and the association between circulating tumor cell enumeration and parathyroid hormone levels may be impactful. The finding that TP53 mutation is more prevalent in patients with distant metastasis may impact further management.

A Case of Parathyroid Carcinoma in Renal Hyperparathyroidism

Introduction

Parathyroid carcinoma is a rare malignant endocrine tumor that is usually associated with primary hyperparathyroidism. The coexistence of parathyroid carcinoma and renal hyperparathyroidism is a rare phenomenon. Hence, we present a case of parathyroid carcinoma in a patient with tertiary hyperparathyroidism.

Case Presentation

Our patient is a 31-year-old woman with a past medical history of end-stage renal failure (ESRF), on hemodialysis for the past 18 years. She was referred by her nephrologist to the endocrine surgery department for consideration of parathyroidectomy in view of long-standing tertiary hyperparathyroidism complicated by hypercalcemia. Bedside ultrasonography scan (US) of the thyroid revealed three parathyroid glands and a hypoechoic right lower pole thyroid nodule with central calcification. Fine-needle aspiration cytology was performed for the suspected thyroid nodule on the same day, which eventually yielded a follicular lesion of undetermined significance. A right hemithyroidectomy and total parathyroidectomy with deltoid implantation was performed. Intraoperative exploration revealed that the thyroid nodule noted at initial US was found to be the right superior parathyroid gland invading into the right thyroid itself. The right superior parathyroid gland was excised en bloc with the right hemithyroidectomy. Post-operatively, the patient was hypocalcemic but was discharged well on post-operative day 5. Histopathological diagnosis of the right hemithyroidectomy specimen containing the right superior parathyroid gland was consistent with that of parathyroid carcinoma.

Conclusion

Parathyroid carcinoma is a rare entity that is difficult to diagnose. In patients with ESRF, the presence of concurrent tertiary hyperparathyroidism makes this even more challenging.

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.

Functional and nonfunctional parathyroid carcinoma: two case reports and literature review

Parathyroid carcinoma (PC) is a rare malignant endocrine tumor. It can be divided into functional and non-functional types according to the tumor's ability to secrete parathyroid hormone. Herein, we present a case each of functional and nonfunctional PC. Case 1: Functional PC. The main clinical symptoms were high parathyroid hormone and hypercalcemia with bone injury and other complications. The mass was large, capsulated, and showed vascular invasion. The tumor was surgically removed, along with a part of the tracheal wall and recurrent laryngeal nerve that were invaded by the tumor. The ipsilateral and isthmus thyroid lobe and central lymph nodes were also removed. Medicines were given to lower blood calcium. The patient died 18 months after surgery because of severe pulmonary infection and tracheal stenosis. Case 2: Non-functional PC. The patient showed no obvious clinical symptoms, but physical examination revealed a thyroid nodule. Despite the small diameter, the mass still invaded the surrounding thyroid lobe, fat, and muscle tissue. Surgery was performed to remove the tumor and ipsilateral thyroid lobe and central lymph nodes. The patient survived without recurrence or metastasis. Thus, we believe that the prognosis of PC negatively correlates with the scope of surgery. Early surgery can improve patient prognosis, and physical examination is conducive to early detection of PC. Herein, we provide a description of the diagnostic workup and the treatment approach and review relevant studies. We summarize the clinicopathological characteristics of PC cases to provide evidence for early diagnosis and therapy, to improve patient prognosis.

Molecular and Clinical Spectrum of Primary Hyperparathyroidism

Recent data suggest an increase in the overall incidence of parathyroid disorders, with primary hyperparathyroidism (PHPT) being the most prevalent parathyroid disorder. PHPT is associated with morbidities (fractures, kidney stones, chronic kidney disease) and increased risk of death. The symptoms of PHPT can be nonspecific, potentially delaying the diagnosis. Approximately 15% of patients with PHPT have an underlying heritable form of PHPT that may be associated with extraparathyroidal manifestations, requiring active surveillance for these manifestations as seen in multiple endocrine neoplasia type 1 and 2A. Genetic testing for heritable forms should be offered to patients with multiglandular disease, recurrent PHPT, young onset PHPT (age ≤40 years), and those with a family history of parathyroid tumors. However, the underlying genetic cause for the majority of patients with heritable forms of PHPT remains unknown. Distinction between sporadic and heritable forms of PHPT is useful in surgical planning for parathyroidectomy and has implications for the family. The genes currently known to be associated with heritable forms of PHPT account for approximately half of sporadic parathyroid tumors. But the genetic cause in approximately half of the sporadic parathyroid tumors remains unknown. Furthermore, there is no systemic therapy for parathyroid carcinoma, a rare but potentially fatal cause of PHPT. Improved understanding of the molecular characteristics of parathyroid tumors will allow us to identify biomarkers for diagnosis and novel targets for therapy.

Clinical and molecular characterization of parathyroid carcinoma in multiple endocrine neoplasia type 1

Nineteen cases of parathyroid carcinoma in patients with multiple endocrine neoplasia type 1 have been reported in the literature, of which 11 carry an inactivating germline mutation in the MEN1 gene. Somatic genetic abnormalities in these parathyroid carcinomas have never been detected. In this paper, we aimed to describe the clinical and molecular characterization of a parathyroid carcinoma identified in a patient with MEN1. A 60-year-old man was diagnosed with primary hyperparathyroidism during the postoperative period of lung carcinoid surgery. Serum calcium and parathyroid hormone levels were 15.0 mg/dL (8.4-10.2) and 472 pg/mL (12-65), respectively. The patient underwent parathyroid surgery, and histological findings were consistent with parathyroid carcinoma. Analysis of the MEN1 gene by next-generation sequencing (NGS) identified a novel germline heterozygous nonsense pathogenic variant (c.978C>A; p.(Tyr326*)), predicted to encode a truncated protein. Genetic analysis of the parathyroid carcinoma revealed a c.307del, p.(Leu103Cysfs*16) frameshift truncating somatic MEN1 variant in the MEN1 gene, which is consistent with MEN1 tumor-suppressor role, confirming its involvement in parathyroid carcinoma etiology. Genetic analysis of CDC73, GCM2, TP53, RB1, AKT1, MTOR, PIK3CA and CCND1 genes in the parathyroid carcinoma DNA did not detect any somatic mutations. To our knowledge, this is the first report of a PC case presenting both germline (first-hit) and somatic (second-hit) inactivation of the MEN1 gene.

[Special features of the diagnostics and treatment of hereditary primary hyperparathyroidism]

Between 2% and 10% of patients with primary hyperparathyroidism (pHPT) are diagnosed with hereditary forms of primary hyperparathyroidism (hpHPT). They are more prevalent in younger patients before the age of 40 years, in patients with persistence or recurrence of pHPT and pHPT patients with multi-glandular disease (MGD). The various forms of hpHPT diseases can be classified into four syndromes, i.e., hpHPT associated with diseases of other organ systems, and four diseases that are confined to the parathyroid glands. Approximately 40% of patients with hpHPT suffer from multiple endocrine neoplasia type 1 (MEN-1) or show germline mutations of the MEN‑1 gene. Currently, germline mutations that lead to a specific diagnosis in patients with hpHPT have currently been described in 13 different genes, which enables a clear diagnosis of the disease; however, a clear genotype-phenotype correlation does not exist, even though the complete loss of a coded protein (e.g. due to frame-shift mutations in the calcium sensing receptor, CASR) often leads to more severe clinical consequences than merely a reduced function of the protein (e.g. due to point mutation). As the various hpHPT diseases require different treatment approaches, which do not correspond to that of sporadic pHPT, a clear definition of the specific form of hpHPT must always be strived for. Therefore, before surgery of a pHPT with clinical, imaging or biochemical suspicion of hpHPT, genetic proof or exclusion of hpHPT is necessary. The differentiated treatment approach for hpHTP can only be defined by taking the clinical and diagnostic results of all the abovenamed findings into account.

Para This, Fibromin That: The Role of CDC73 in Parathyroid Tumors and Familial Tumor Syndromes

CDC73 alterations are associated with three main parathyroid lesions according to the World Health Organization (WHO) classification of tumors of the endocrine system. These include hyperparathyroidism-jaw tumor (HPT-JT) syndrome-associated adenomas, atypical parathyroid tumors (APTs), and parathyroid carcinomas (PCs). The loss of nuclear parafibromin expression, which serves as a surrogate marker for the underlying CDC73 alteration, encompasses these tumors under the term parafibromin-deficient parathyroid tumors. They have distinct morphologic features of more abundant eosinophilic cytoplasm with perinuclear clearing surrounding a large nucleus as well as prominent dilated branching "hemangiopericytoma-like" vasculature and a thick capsule as well as variably sized cystic spaces. These tumors include cases that show unequivocal histologic features fulfilling the criteria for PCs with growing data indicating a higher rate of recurrence or metastasis compared with parafibromin intact PCs. More importantly, the loss of parafibromin expression can be used in clinical practice to recognize APTs that fall short of a conclusive diagnosis of PCs, but clinically behave akin to them. Moreover, recognizing these tumors can lead to an underlying germline mutation and a diagnosis of HPT-JT, which impacts long-term treatment and surveillance for patients and close family.

Novel PRUNE2 Germline Mutations in Aggressive and Benign Parathyroid Neoplasms

Parathyroid tumors are mostly sporadic but can also occur in familial forms, including different kinds of genetic syndromes with varying phenotypes and penetrance. Recently, somatic mutations of the tumor suppressor gene PRUNE2 were found to be frequent in parathyroid cancer (PC). The germline mutation status of PRUNE2 was investigated in a large cohort of patients with parathyroid tumors from the genetically homogenous Finnish population, 15 of which had PC, 16 atypical parathyroid tumors (APT), and 6 benign parathyroid adenomas (PA). Mutations in previously established hyperparathyroidism-related genes were screened with a targeted gene panel analysis. Nine PRUNE2 germline mutations with a minor allele frequency (MAF) of <0.05 were found in our cohort. Five of these were predicted to be potentially damaging and were identified in two patients with PC, two with APT, and three with PA. The mutational status was not associated with the tumor group nor related to the clinical picture or severity of the disease. Still, the frequent finding of rare germline mutations of PRUNE2 may point to the gene playing a role in the pathogenesis of parathyroid neoplasms.

Clinical and genetic analysis of atypical parathyroid adenoma compared with parathyroid carcinoma and benign lesions in a Chinese cohort

CONTEXT

The malignant potential and molecular signature of atypical parathyroid adenoma (APA) remain elusive. Data from Asia are still lacking.

DESIGN AND SETTING

This was a retrospective study on a large APA cohort in a single center from mainland China.

METHODS

A total of 320 patients with primary hyperparathyroidism (PHPT), containing 79 APA, 79 Parathyroid cancer (PC) and 162 benign lesions cases, were enrolled after surgery for collection of clinical data and genetic analysis.

RESULTS

APA patients showed earlier mean onset age than benign group (46.9 ± 17.1 vs. 52.0 ± 14.3 yrs). Less bone involvement and gastrointestinal symptoms were presented in APA compared to PC (35.4% vs. 62.0%, and 17.7% vs. 41.8%), while more urolithiasis was seen in APA than in benign lesions (57.0% vs. 29.6%). The APA group had moderate hypercalcemia (mean 3.02 ± 0.44mmol/L) with elevated serum PTH (median 593.0pg/ml) and proportion of hypercalcemic crisis as 22.8%, all higher than those of benign lesions but lower than those of PC group. The recurrence/no remission rate of the APA group was significantly lower than that of the PC and similar to the benign group (5.1% vs. 31.6% vs. 3.1%). Germline CDC73 mutation was the most common molecular abnormality in both PC and APA subjects. APA patients with nonsynonymous germline variants showed earlier onset age (28.5 ± 16.9 vs. 48.1 ± 17.7 yrs) and more cases developing no remission/recurrence (25.0% vs. 0.0%).

CONCLUSIONS

Patients with APA presented clinical and biochemical characteristics much less severe than PC and resembling the benign neoplasms, with a relatively good prognosis. Germline gene variations were associated with earlier onset and probably more recurrence of PHPT in APA.

Advances and Updates in Parathyroid Pathology

Hyperparathyroidism is a common endocrine disorder characterized by elevated levels of parathyroid hormone and hypercalcemia and is divided into 3 types: primary, secondary, and tertiary. Distinction between these types is accomplished by correlation of clinical, radiologic, and laboratory findings with pathologic features. Primary hyperparathyroidism occurs sporadically in 85% of cases with the remaining cases associated with multiple familial syndromes. The pathologic manifestations of primary hyperparathyroidism include parathyroid adenoma, parathyroid hyperplasia, and parathyroid carcinoma. Recent advances in the understanding of the pathogenesis of parathyroid disease has helped to refine the diagnosis and classification of parathyroid lesions. The identification of multiple clonal proliferations in traditional multiglandular parathyroid hyperplasia has led to the adoption by the World Health Organization (WHO) of the alternate term of primary hyperparathyroidism-related multiglandular parathyroid disease. Additional nomenclature changes include the adoption of the term atypical parathyroid tumor in lieu of atypical parathyroid adenoma to reflect the uncertain malignant potential of these neoplasms. Clinical and morphologic features characteristic of familial disease have been described that can help the practicing pathologist identify underlying familial disease and provide appropriate management. Use of ancillary immunohistochemistry and molecular studies can be helpful in classifying parathyroid neoplasms. Parafibromin has proven useful as a diagnostic and prognostic marker in atypical parathyroid tumors and parathyroid carcinomas. This review provides an update on the diagnosis and classification of parathyroid lesions considering the recent advances in the understanding of the molecular and clinical features of parathyroid disease and highlights the use of ancillary studies (immunohistochemical, and molecular) to refine the diagnosis of parathyroid lesions.

Updates of Genomics and Proteomics of Parathyroid Carcinoma

Parathyroid carcinoma is a rare disease that needs an additional diagnostic tool and wide therapeutic options. The genomics and proteomics approach may help to find the tools to improve the prognosis of the disease by early detection and metastatic control. The findings from genomics were mainly CDC73, PRUNE2, CCND1, and genes related to PI3K/AKT/mTOR and Wnt pathways. CDC73, PRUNE2, and CCND1 were closely related to each other, and PRUNE2 and CCND1 genes are related to expression levels of parafibromin protein, which may aid in supporting the definite diagnosis of the disease. PI3K/AKT/mTOR and Wnt pathways could be a potential therapeutic target for the disease, which needs further basket trials to prove the concept. In this review, current findings from genomics and proteomics studies in parathyroid carcinoma were reviewed.

Epidemiology, Pathophysiology, and Genetics of Primary Hyperparathyroidism

In this narrative review, we present data gathered over four decades (1980-2020) on the epidemiology, pathophysiology and genetics of primary hyperparathyroidism (PHPT). PHPT is typically a disease of postmenopausal women, but its prevalence and incidence vary globally and depend on a number of factors, the most important being the availability to measure serum calcium and parathyroid hormone levels for screening. In the Western world, the change in presentation to asymptomatic PHPT is likely to occur, over time also, in Eastern regions. The selection of the population to be screened will, of course, affect the epidemiological data (ie, general practice as opposed to tertiary center). Parathyroid hormone has a pivotal role in regulating calcium homeostasis; small changes in extracellular Ca++ concentrations are detected by parathyroid cells, which express calcium-sensing receptors (CaSRs). Clonally dysregulated overgrowth of one or more parathyroid glands together with reduced expression of CaSRs is the most important pathophysiologic basis of PHPT. The spectrum of skeletal disease reflects different degrees of dysregulated bone remodeling. Intestinal calcium hyperabsorption together with increased bone resorption lead to increased filtered load of calcium that, in addition to other metabolic factors, predispose to the appearance of calcium-containing kidney stones. A genetic basis of PHPT can be identified in about 10% of all cases. These may occur as a part of multiple endocrine neoplasia syndromes (MEN1-MEN4), or the hyperparathyroidism jaw-tumor syndrome, or it may be caused by nonsyndromic isolated endocrinopathy, such as familial isolated PHPT and neonatal severe hyperparathyroidism. DNA testing may have value in: confirming the clinical diagnosis in a proband; eg, by distinguishing PHPT from familial hypocalciuric hypercalcemia (FHH). Mutation-specific carrier testing can be performed on a proband's relatives and identify where the proband is a mutation carrier, ruling out phenocopies that may confound the diagnosis; and potentially prevention via prenatal/preimplantation diagnosis. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Genetics of monogenic disorders of calcium and bone metabolism

Disorders of calcium homeostasis are the most frequent metabolic bone and mineral disease encountered by endocrinologists. These disorders usually manifest as primary hyperparathyroidism (PHPT) or hypoparathyroidism (HP), which have a monogenic aetiology in 5%-10% of cases, and may occur as an isolated endocrinopathy, or as part of a complex syndrome. The recognition and diagnosis of these disorders is important to facilitate the most appropriate management of the patient, with regard to both the calcium-related phenotype and any associated clinical features, and also to allow the identification of other family members who may be at risk of disease. Genetic testing forms an important tool in the investigation of PHPT and HP patients and is usually reserved for those deemed to be an increased risk of a monogenic disorder. However, identifying those suitable for testing requires a thorough clinical evaluation of the patient, as well as an understanding of the diversity of relevant phenotypes and their genetic basis. This review aims to provide an overview of the genetic basis of monogenic metabolic bone and mineral disorders, primarily focusing on those associated with abnormal calcium homeostasis, and aims to provide a practical guide to the implementation of genetic testing in the clinic.

Atypical parathyroid adenoma: Series of two consecutive cases from a tertiary care hospital in Qatar

INTRODUCTION

Atypical parathyroid adenomas (APA) are an uncommon cause of hypercalcemia and comprise a minority of parathyroid adenomas.

PRESENTATION OF CASES

Case 1 - Egyptian male, 48 years old with history of type 2 diabetes mellitus, incidentally discovered increased serum of calcium level on routine investigation, was diagnosed as PHPT, US and MIBI scan showed large left inferior parathyroid adenoma, focused exploration and excision of the APA was undertaken, histopathology confirmed APA. Case 2 - Egyptian male, 60 years old, cardiac patient with history of diabetes, hypertension and multiple cardiac interventions, had nausea, vomiting, constipation abdominal pain, polyuria, polydipsia, and history of passing renal stones, hypercalcemia workup showed primary hyperparathyroidism (PHPT), MIBI was negative and SPECT scan suggested right inferior parathyroid adenoma, focused exploration and excision of the APA was undertaken, histopathology confirmed APA.

DISCUSSION

APA are an uncommon cause of hypercalcemia and are responsible for a minority of parathyroid adenomas. Combined US and MIBI and SPECT scans can detect APA. Focused exploration and excision of the APA under general anaesthesia can completely remove the APA.

CONCLUSION

Awareness of the physician and a high index of suspicion to symptoms or signs that could reflect an underlying PHPT is essential. Yearly biochemical and neck US follow up are required to detect any risk of recurrence or malignancy in the long term.

USP37 Deubiquitinates CDC73 in HPT-JT Syndrome

The CDC73/HRPT2 gene, a defect which causes hyperparathyroidism–jaw tumor (HPT-JT) syndrome, encodes CDC73/parafibromin. We aimed to investigate whether CDC73 would be a target for ubiquitin–proteasome degradation. We cloned full-length cDNAs encoding a family of 58 ubiquitin-specific deubiquitinating enzymes (DUBs), also known as ubiquitin-specific proteases (USPs). Use of the yeast two-hybrid system then enabled us to identify USP37 as interacting with CDC73. The biochemical interaction between the USP37 and CDC73 and their reciprocal binding domains were studied. Co-localization of CDC73 and USP37 was observed in cells. CDC73 was found to be polyubiquitinated, and polyubiquitination of CDC73 was prominent in mutants. CDC73 was deubiquitinated via K48-specific ubiquitin chains by USP37, but not by the catalytically inactive USP37^C350S mutant. Observation of the binding between deletion mutants of CDC73 and USP37 revealed that the β-catenin binding site of CDC73 and the ubiquitin-interacting motifs 2 and 3 (UIM2 and 3) of USP37 were responsible for the interaction between the two proteins. Moreover, these two enzymes co-existed within the nucleus of COS7 cells. We conclude that USP37 is a DUB for CDC73 and that the two proteins interact through specific domains, suggesting that USP37 is responsible for the stability of CDC73 in HPT-JT syndrome.

Mortality factors in recurrent parathyroid cancer: a pooled analysis

INTRODUCTION

Parathyroid cancer is a rare disease with high recurrence rate. The prognostic factors for recurrent parathyroid cancer are yet to be ascertained. We aimed to establish the association between recurrent parathyroid cancer and previously reported prognostic factors.

MATERIALS AND METHODS

We conducted a PubMed search using the keywords 'parathyroid cancer', 'parathyroid neoplasm', and 'hypercalcemia' during 1966-2019 and included 3272 articles. We focused on 73 patients with recurrent parathyroid cancer from 55 studies. We conducted a survival analysis using the Cox proportional hazards model with 95% confidence interval.

RESULTS

For the 73 patients included in the analysis, the mean age (± standard deviation) was 44 ± 13.2 years, wherein 36 patients were women (49.3%). During the 5236 person-months at risk (mean follow-up 71.7 months, range 3-264), 38 patients died. The incidence of local recurrence, lymph-node metastasis, lung metastasis, and bone metastasis were 60.3, 12.3, 56.2, and 24.7, respectively. Bone metastasis, disease-free interval < 1 year, and total surgeries < 3 were significant prognostic factors in univariate analysis (log-rank test P = 0.0063, P = 0.0006, and P = 0.0056, respectively). In the multivariate-adjusted analysis, the mortality risk was significantly increased in patients with bone metastasis with a hazard ratio (HR) of 4.83 (95% CI 1.16-20.2; P = 0.03), disease-free interval <=1 year of 5.92 (95% CI 1.85-18.99; P = 0.003), and total surgeries <3 of 11.29 (95% CI 2.82-45.22; P = 0.001), considering these as possible predictive prognostic factors.

CONCLUSION

Bone metastasis, duration of disease-free interval, and total number of surgeries predict survival in recurrent parathyroid cancer.

Parathyroid Carcinoma: a Review

Parathyroid cancer is a rare endocrine malignancy with only a few thousand cases reported worldwide. As a result, there exists considerable controversy regarding the various aspects of this disease, viz., etiology, diagnosis, and management. We hereby attempt to review the literature on parathyroid carcinoma (PC) and summarize the practices based on the current evidence available. The majority of the PC are sporadic although an association with hyperparathyroidism-jaw tumor syndrome, multiple endocrine neoplasia (MEN) 1 and 2, and isolated familial hyperparathyroidism has been shown. As preoperative diagnosis is challenging, PC should be suspected in patients presenting with a neck mass with signs and symptoms of invasion to surrounding structures. Skeletal and renal symptoms are often associated with PC as presenting complaints. The biochemical parameters are more pronounced in the case of PC compared with benign countpart. Due to its rarity, the American Joint Committee of cancer control (AJCC) acknowledges that as yet a clear distinct staging system to prognosticate the disease would be premature. Complete excision with negative margins at first surgery offers the best chance of cure. The role of radiotherapy (RT) is still unclear; however few series have suggested a better locoregional control with adjuvant RT. Recurrences are common and are most significantly associated with an incomplete clearance at initial surgery. Surgical salvage of recurrent/metastatic disease with medical management of hypercalcemia is the treatment of choice. Large prospective studies and trials need to be conducted to understand the pathology better and improve management protocols; however this is a challenge due to rarity of cases.

MicroRNA Profile Alterations in Parathyroid Carcinoma: Latest Updates and Perspectives

Simple Summary

Despite the considerable development of diagnostic tools, distinguishing between benign and malignant parathyroid tumors poses a significant diagnostic challenge. Epigenetic regulations, including noncoding microRNAs (miRNAs), have recently emerged as a new and promising source of biomarkers. MiRNAs are post-transcriptional regulators of gene expression. These tissue-specific molecules are known to be deregulated between cancer and normal cells. This review delineates changes in miRNA expression in parathyroid carcinoma (PC), advancing our understanding of PC tumorigenesis and emphasizing, at the same time, that miRNAs can be further exploited for diagnostic and therapeutic purposes.

Abstract

Parathyroid tumors are a genetically heterogenous group with a significant variability in clinical features. Due to a lack of specific signs and symptoms and uncertain histopathological criteria, parathyroid carcinomas (PCs) are challenging to diagnose, both before and after surgery. There is a great interest in searching for accurate molecular biomarkers for early detection, disease monitoring, and clinical management. Due to improvements in molecular pathology, the latest studies have reported that PC tumorigenesis is strongly linked to the epigenetic regulation of gene expression. MicroRNA (miRNA) profiling may serve as a helpful adjunct in distinguishing parathyroid adenoma (PAd) from PC and provide further insight into regulatory pathways involved in PTH release and parathyroid tumorigenesis. So far, only a few studies have attempted to show the miRNA signature for PC, and very few overlaps could be found between these relatively similar studies. A global miRNA downregulation was detected in PC compared with normal glands among differentially expressed miRNAs. This review summarizes changes in miRNA expression in PC and discusses the future research directions in this area.

Parathyroid Carcinoma All-In-One, a Rare Life-Threatening Case With Multiple Systemic Manifestations: Case Report and Review of the Literature

Parathyroid carcinoma (PC) is an extremely rare disease. Although it may occasionally occur in genetic syndromes, it is more often sporadic. It is usually associated with a consistent secretion of PTH, causing severe hypercalcemia and potentially all clinical conditions due to primary hyperparathyroidism. Management of PC can be challenging: some clinical, biochemical, and radiological features may be useful, but the final diagnosis of malignancy strictly relies on histological criteria. To date, radical surgery is the first-choice treatment and is the only effective therapy to control hypercalcemia and other clinical manifestations. On the other hand, chemo- or radiotherapy, local treatments, or novel drugs should be reserved for selected cases. We report an exceptionally unusual case of life-threatening PC, associated with several systemic manifestations: moderate pancreatitis, portal thrombosis, kidney stones, brown tumors, osteoporosis, hungry bone syndrome (HBS), chondrocalcinosis, neuropathy, and depression. The clinical case also represents an opportunity to provide a review of the recent literature, associated with a complete evaluation of the main diagnostic and therapeutic approaches.

Genetics and Epigenetics of Parathyroid Carcinoma

Parathyroid carcinoma (PC) is an extremely rare malignancy, accounting less than 1% of all parathyroid neoplasms, and an uncommon cause of primary hyperparathyroidism (PHPT), characterized by an excessive secretion of parathyroid hormone (PTH) and severe hypercalcemia. As opposed to parathyroid hyperplasia and adenomas, PC is associated with a poor prognosis, due to a commonly unmanageable hypercalcemia, which accounts for death in the majority of cases, and an overall survival rate of 78-85% and 49-70% at 5 and 10 years after diagnosis, respectively. No definitively effective therapies for PC are currently available. The mainly employed treatment for PC is the surgical removal of tumoral gland(s). Post-surgical persistent or recurrent disease manifest in about 50% of patients. The comprehension of genetic and epigenetic bases and molecular pathways that characterize parathyroid carcinogenesis is important to distinguish malignant PCs from benign adenomas, and to identify specific targets for novel therapies. Germline heterozygote inactivating mutations of the CDC73 tumor suppressor gene, with somatic loss of heterozygosity at 1q31.2 locus, account for about 50-75% of familial cases; over 75% of sporadic PCs harbor biallelic somatic inactivation/loss of CDC73. Recurrent mutations of the PRUNE2 gene, a recurrent mutation in the ADCK1 gene, genetic amplification of the CCND1 gene, alterations of the PI3K/AKT/mTOR signaling pathway, and modifications of microRNA expression profile and gene promoter methylation pattern have all been detected in PC. Here, we review the current knowledge on gene mutations and epigenetic changes that have been associated with the development of PC, in both familial and sporadic forms of this malignancy.

Hereditary Primary Hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a commonly encountered clinical problem and occurs as part of an inherited disorder in ∼10% of patients. Several features may alert the clinician to the possibility of a hereditary PHPT disorder (eg, young age of disease onset) whilst establishing any relevant family history is essential to the clinical evaluation and will help inform the diagnosis. Genetic testing should be offered to patients at risk of a hereditary PHPT disorder, as this may improve management and allow the identification and investigation of other family members who may also be at risk of disease.

Parathyroid Carcinoma and Ectopic Secretion of Parathyroid hormone

The most common causes of hypercalcemia are primary hyperparathyroidism (PHPT) and malignancy. Parathyroid carcinoma (PC), causing a severe PHPT, is the rarest parathyroid tumor. A diagnosis of PC is challenging because the clinical profile overlaps with that of benign counterpart. Surgery is the mainstay treatment. CDC73 mutations have been detected in up to 80% of sporadic PCs. Ectopic production of parathyroid hormone (PTH) by malignant nonparathyroid tumors is a rare condition accounting for less than 1% of hypercalcemia of malignancy. PTH secretion can be considered an aberration in the tissue specificity of gene expression and may involve heterogeneous molecular mechanisms.

[Sporadic primary hyperparathyroidism with multiple parathyroid adenomas]

Multiple lesions of the parathyroid glands (PTG) in primary hyperparathyroidism (PHPT) can be sporadic or develop as part of hereditary syndromes, manifesting at young age. There the description of a severe sporadic PHPT with big parathyroid neoplasms in the young patient is presented. Clinical data made it possible to suspect MEN-1 syndrome or parathyroid carcinomas; however, mutations CDKN, CDC73, MEN1 were excluded. The patient underwent removal of three identified tumors: benign adenomas of the left PTG and hyperplasia of the right one. Postoperative hypocalcemia and severe hungry bone syndrome required the administration of vitamin D and calcium carbonate preparations. However, a year after the operation, a «mild» recurrent disease was confirmed. Taking into account the patient's refusal to reoperation and a significant improvement of the target organs state, active observation was continued. The patient needs further careful dynamic monitoring by specialists in order to timely identify indications for repeated surgical treatment to improve the life quality and span.

Parathyroid Carcinoma and Adenoma Co-existing in One Patient: Case Report and Comparative Proteomic Analysis

BACKGROUND/AIM

The lack of specific parathyroid carcinoma (PC) biomarkers in clinical practice points out the importance of analyzing the proteomic signature of this cancer. We performed a comparative proteomic analysis of PC and parathyroid adenoma (PA) co-existing in the same patient.

PATIENTS AND METHODS

PC and PA were taken from a 63-year-old patient. Using two-dimensional differential gel electrophoresis (2D-DIGE) coupled to mass spectrometry we examined the differences between PC and PA proteins. For validation, additional PC and PA samples were obtained from 10 patients. Western blot analysis was used to validate the difference of expression observed with 2D-DIGE analysis. Bioinfomatic analysis was performed using QIAGEN's Ingenuity Pathways Analysis (IPA) to determine the predominant canonical pathways and interaction networks involved.

RESULTS

Thirty-three differentially expressed proteins were identified in PC compared to PA. Among these, ubiquitin C-terminal hydrolase-L1 (UCH-L1) was highly overexpressed in PC. The result was confirmed by Western Blot analysis in additional PC samples.

CONCLUSION

Our comparative proteomic analysis of co-existing neoplasms allowed detecting specific and peculiar differences between PC and PA overcoming population biological variability.

Do Patients With Atypical Parathyroid Adenoma Need Close Follow-up?

CONTEXT

Atypical parathyroid adenomas (APAs) are neoplasms with uncertain malignant potential but lack unequivocal histological signs of malignancy.

OBJECTIVE

This work aims to retrospectively evaluate the clinical and biochemical profiles of patients with APA, the outcome after parathyroidectomy (PTX), and the presence of CDC73 germline and somatic mutations.

METHODS

This monocentric study was conducted on consecutive patients undergoing PTX for primary hyperparathyroidism (PHPT) between June 2000 and December 2020. Fifty-eight patients with a confirmed histopathological diagnosis of APA, and age- and sex-matched controls with parathyroid adenoma (PA) were also included.

RESULTS

Fifty-four patients had sporadic PHPT and 4 had familial isolated hyperparathyroidism (FIHP). Thirty-four patients (59%) had symptomatic disease. Serum calcium and parathyroid hormone (PTH) levels were significantly higher in symptomatic compared to asymptomatic patients (P = .048 and .008, respectively). FIHP patients were younger than their sporadic counterparts (30 ± 17 years vs 55 ± 13 years). APA patients had significantly higher serum calcium and PTH levels and lower 25-hydroxyvitamin D concentration, bone mineral density, and T score at one-third distal radius compared to those with PA. Four of 56 APA patients displayed a CDC73 germline mutation. No somatic CDC73 mutation was identified in 24 tumor specimens. The mean follow-up after surgery was 60 ± 56.4 months. All but 6 patients (90%), 5 with apparently sporadic PHPT and 1 with FIHP, were cured after surgery.

CONCLUSION

The large majority of patients with APA, despite a moderate/severe phenotype, have a good prognosis. Germline CDC73 mutation-positive patients had a higher rate of persistent/recurrent disease. CDC73 gene alterations do not seem to have a relevant role in the tumorigenesis of sporadic APA.

Parathyroid Tumors: Molecular Signatures

Parathyroid tumors are rare endocrine neoplasms affecting 0.1–0.3% of the general population, including benign parathyroid adenomas (PAs; about 98% of cases), intermediate atypical parathyroid adenomas (aPAs; 1.2–1.3% of cases) and malignant metastatic parathyroid carcinomas (PCs; less than 1% of cases). These tumors are characterized by a variable spectrum of clinical phenotypes and an elevated cellular, histological and molecular heterogeneity that make it difficult to pre-operatively distinguish PAs, aPAs and PCs. Thorough knowledge of genetic, epigenetic, and molecular signatures, which characterize different parathyroid tumor subtypes and drive different tumorigeneses, is a key step to identify potential diagnostic biomarkers able to distinguish among different parathyroid neoplastic types, as well as provide novel therapeutic targets and strategies for these rare neoplasms, which are still a clinical and therapeutic challenge. Here, we review the current knowledge on gene mutations and epigenetic changes that have been associated with the development of different clinical types of parathyroid tumors, both in familial and sporadic forms of these endocrine neoplasms.

Distinguishing Parathyromatosis, Atypical Parathyroid Adenomas, and Parathyroid Carcinomas Utilizing Histologic and Clinical Features

Parathyromatosis is displaced parathyroid tissue in the neck and mediastinum related to prior surgery. Parathyromatosis can be difficult to distinguish from atypical adenoma and parathyroid carcinoma. The aim of this study is to evaluate clinical and morphologic features that may differentiate parathyromatosis, atypical adenoma, and parathyroid carcinoma. Cases of parathyromatosis, atypical adenoma, and parathyroid carcinoma were identified. Index cases were reviewed by consensus for histologic features, including stromal, cytologic/architectural, and invasive features. Ki67 was performed on index cases and scored using the Adsay method. Clinical information was gathered from the electronic medical record. 4 parathyromatosis, 17 atypical adenoma, and 6 parathyroid carcinoma were included. Parathyroid carcinomas were more likely to display coarse chromatin with nucleoli (P = 0.04), infiltrative invasion (P < 0.01), and metastasis (P < 0.01). Only parathyromatosis showed circumscribed invasion. Infiltrative invasion was more common in cases with progression (P = 0.046) and metastasis (P < 0.001). Necrosis and perineural invasion were only present in cases with progression and were more frequent in cases with metastasis (P = 0.079 and P = 0.19, respectively). There were no differences in presence of a fibrous capsule, capsular invasion, intralesional fibrous bands, random endocrine atypia, solid growth, Ki67 index, gland size/weight, serum PTH/calcium levels, and locoregional recurrence rates. There is overlap in the histologic features in parathyromatosis, atypical adenoma, and parathyroid carcinoma. While perineural, vascular, and infiltrative soft tissue invasion should remain diagnostic of malignancy, other atypical features such as solid growth, coarse chromatin with nucleoli, and necrosis should raise concern for recurrence and/or metastasis, and can be present in parathyroid lesions with and without recurrence.

Parafibromin Abnormalities in Ossifying Fibroma

Ossifying fibromas are very rare tumors that are sometimes seen as part of the hyperparathyroidism-jaw tumor syndrome (HPT-JT), which is caused by inactivating mutations of the HRPT2/CDC73 tumor suppressor gene. CDC73 mutations have been identified in a subset of sporadic cases but aberrant expression of the encoded protein, parafibromin, has not been demonstrated in ossifying fibroma. We sought to determine if loss of parafibromin regularly contributes to the development of sporadic, nonsyndromic ossifying fibroma. We examined a series of 9 ossifying fibromas, including ossifying, cemento-ossifying, and juvenile active variants, for parafibromin protein expression by immunohistochemistry and for CDC73 sequence abnormalities by Sanger sequencing and/or targeted AmpliSeq panel sequencing. Four ossifying fibromas showed a complete absence of nuclear parafibromin expression; loss of parafibromin expression was coupled with aberrant cytoplasmic parafibromin expression in 1 case. CDC73 mutations were detected in 2 cases with aberrant parafibromin expression. These results provide novel evidence, at the level of protein expression, that loss of the parathyroid CDC73/parafibromin tumor suppressor may play a role in the pathogenesis of a subset of ossifying fibromas.

Genetic Alteration Profiles and Clinicopathological Associations in Atypical Parathyroid Adenoma

Genomic aberrations associated with atypical parathyroid adenoma (AA) are poorly understood. Thus, herein, we sought to expand our current understanding of the molecular basis of atypical parathyroid adenomas. We analyzed 134 samples that had been surgically obtained from parathyroid tumors, including parathyroid carcinomas, atypical parathyroid adenomas, and parathyroid adenomas. The tumors were harvested from formalin-fixed, paraffin-embedded tissues. Fifteen tumor-related genes from recently published genome sequencing data were subjected to targeted sequencing analysis, and an average sequencing depth of 500x was achieved. Sixteen (16/50, 32%) AA tumors harbored at least one of the following genomic alterations: CDC73 (12, 24%), EZH2 (4, 8%), HIC1 (1, 2%), and CDKN2A (1, 2%). Our study identified, for the first time, a relatively high frequency of genomic alterations in patients with AA in a Chinese population. This suggests that AA arises de novo, rather than developing from a parathyroid adenoma. Altogether, these findings will improve our understanding of the malignant potential of parathyroid tumors at the molecular level.

Parathyroid cancer: A systematic review of diagnostic biomarkers

INTRODUCTION

Parathyroid cancers are rare and difficult to distinguish from benign parathyroid tumours. Prediction of malignancy often relies on intraoperative assessment of invasion. Standard histology is also inadequate; especially in the absence of local invasion, lymph nodal disease and metastasis. The aim of this project was to systematically review published literature on potential bio-markers used for the diagnosis of parathyroid cancer.

METHODS

Pubmed, Web of Science and Medline databases were searched. Inclusion criteria included English language papers published after 1985 and reporting on biomarkers in human studies of parathyroid cancer and benign disease.

RESULTS

118 relevant papers were appraised; all were observational studies. At least 2 papers studied 8 serum, 4 urine and 27 tissue biomarkers on the diagnosis of parathyroid cancer. Of these, 5 serum and 13 tissue markers have been demonstrated in at least one study to be statistically different in benign and malignant disease. We present a synthesis of data for each biomarker and measures of diagnostic accuracy where possible.

CONCLUSIONS

Consideration should be given to the use of a panel of biomarkers to review patients with suspected parathyroid cancer. A profile including serum calcium and PTH levels and tissue expression of APC, Parafibromin, PGP9.5, Galectin 3 and Ki67 is proposed. Systematic Review Registration Number - CRD42019127833.

Multiple Endocrine Neoplasia Type 1 (MEN1) 5'UTR Deletion, in MEN1 Family, Decreases Menin Expression

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by the occurrence of parathyroid, pancreatic and pituitary tumors, and is due to mutations in the coding region of the MEN1 gene, which encodes menin. We investigated a family with identical twins that had MEN1, with different MEN1 tumors. DNA sequence analysis of the MEN1 coding region had not identified any abnormalities and we hypothesized that deletions and mutations involving the untranslated regions may be involved. Informed consent and venous blood samples were obtained from five family members. Sanger DNA sequencing and multiplex ligation-dependent probe amplification (MLPA) analyses were performed using leukocyte DNA. This revealed a heterozygous 596bp deletion (Δ596bp) between nucleotides -1087 and -492 upstream of the translation start site, located within the MEN1 5' untranslated region (UTR), and includes the core promoter and multiple cis-regulatory regions. To investigate the effects of this 5'UTR deletion on MEN1 promoter activity, we generated luciferase reporter constructs, containing either wild-type 842bp or mutant 246bp MEN1 promoter, and transfected them into human embryonic kidney HEK293 and pancreatic neuroendocrine tumor BON-1 cells. This revealed the Δ596bp mutation to result in significant reductions by 37-fold (p < 0.0001) and 16-fold (p < 0.0001) in luciferase expression in HEK293 and BON-1 cells, respectively, compared to wild-type. The effects of this 5'UTR deletion on MEN1 transcription and translation were assessed using qRT-PCR and Western blot analyses, respectively, of mRNA and protein lysates obtained from Epstein-Barr-virus transformed lymphoblastoid cells derived from affected and unaffected individuals. This demonstrated the Δ596bp mutation to result in significant reductions of 84% (p < 0.05) and 88% (p < 0.05) in MEN1 mRNA and menin protein, respectively, compared to unaffected individuals. Thus, our results report the first germline MEN1 5'UTR mutation and highlight the importance of investigating UTRs in MEN1 patients who do not have coding region mutations. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

The Oncosuppressors MEN1 and CDC73 Are Involved in lncRNA Deregulation in Human Parathyroid Tumors

A role for long non-coding RNAs (lncRNAs) in endocrine cancer pathogenesis is emerging. However, knowledge regarding their expression pattern, correlation with known genetic defects, and clinical implications in parathyroid tumors is still unclear. Here, we profiled 90 known lncRNAs in a first series of normal (PaN = 2), adenomatous (PAd = 12), and carcinomatous (PCa = 4) parathyroid glands and we confirmed deregulation of 11 lncRNAs using an independent cohort of patients (PaN = 4; PAd = 26; PCa = 9). Expression of lncRNAs was correlated with cytogenetic aberrations, status of genes multiple endocrine neoplasia 1 (MEN1) and cell division cycle 73 (CDC73), or clinical features. Globally, lncRNAs discriminate according to tissue histology. BC200 consistently identifies parathyroid cancers from adenomas and atypical adenomas. Loss-of-heterozygosity (LOH) at chromosomes 1, 11, 15, 21, and 22 significantly impacts expression of lncRNAs in PAds. Silencing of the key parathyroid gene MEN1 modulates the expression of six lncRNAs in primary PAds-derived cultures. Analogous levels of lncRNAs are measured in PAds with the mutation in the MEN1 gene compared with PAds with wild-type MEN1. Similarly, carcinomas with mutated CDC73 differ from PCas with wild-type protein in terms of expression of lncRNAs. PCas harboring CDC73 mutations overexpress BC200 compared to wild-type carcinomas. Overall, these findings shed light on deregulation of lncRNAs in human parathyroid tumors and propose that circuits between lncRNAs and the oncosuppressors MEN1 or CDC73 may have a role in parathyroid tumorigenesis as epigenetic modulators. © 2020 American Society for Bone and Mineral Research (ASBMR).

A Novel Germline c.1267T>A MEN1 Mutation in MEN1 Family—from Phenotype to Gene and Back

Primary hyperparathyroidism is a relatively common endocrine disorder, which may be hereditary. This report describes clinical, biochemical, radiographic, and genetic findings, the latter obtained using next generation sequencing (NGS), in three consanguineous patients. Gene panels in NGS consisted of 5 or 70 genes, including MEN1 and RET. The first patient suffered from recurrent primary hyperparathyroidism. Primary hyperparathyroidism and pituitary microadenomas were afterwards diagnosed in two of her daughters. No clinical nor radiological features of gastroenteropancreatic neuroendocrine tumors were found. All three family members were heterozygous for MEN1 NM_130799: c.1267T>A transversion, which is predicted to result in substitution of tryptophan with arginine in position 423. Additionally, the first patient was also a carrier of RET NM_020975: c.1946C>T missense mutation, which was not present in two other family members. We describe a family with a novel heterozygous mutation (NM_130799: c.1267T>A) in MEN1 gene and postulate that it leads to MEN1 syndrome. The study underlies the importance of genetic testing in primary hyperparathyroidism in personalizing patients’ care.

Multiple Endocrine Neoplasia Type 1 (MEN1) Phenocopy Due to a Cell Cycle Division 73 (CDC73) Variant

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by the combined occurrence of parathyroid tumors, pituitary adenomas, and pancreatic neuroendocrine neoplasms (PNENs). MEN1 is caused by germline MEN1 mutations in > 75% of patients, and the remaining 25% of patients may have mutations in unidentified genes or represent phenocopies with mutations in genes such as cell cycle division 73 (CDC73), the calcium sensing receptor (CASR), and cyclin-dependent kinase inhibitor 1B (CDKN1B), which are associated with the hyperparathyroidism-jaw tumor syndrome, familial hypocalciuric hypercalcemia type 1, and MEN4, respectively. Here, we report a heterozygous c.1138C>T (p.Leu380Phe) CDC73 germline variant in a clinically diagnosed MEN1 patient, based on combined occurrence of primary hyperparathyroidism, acromegaly, and a PNEN. Characterization of the PNEN confirmed it was a neuroendocrine neoplasm as it immuno-stained positively for chromogranin and glucagon. The rare variant p.Leu380Phe occurred in a highly conserved residue, and further analysis using RNA-Scope indicated that it was associated with a significant reduction in CDC73 expression in the PNEN. Previously, CDC73 mutations have been reported to be associated with tumors of the parathyroids, kidneys, uterus, and exocrine pancreas. Thus, our report of a patient with PNEN and somatotrophinoma who had a CDC73 variant, provides further evidence that CDC73 variants may result in a MEN1 phenocopy.

Outcome of Clinical Genetic Testing in Patients with Features Suggestive for Hereditary Predisposition to PTH-Mediated Hypercalcemia

Primary hyperparathyroidism (pHPT) is associated with familial syndromes such as multiple endocrine neoplasia type 1 (MEN1), 2A (MEN2A), MEN-like syndromes (CDKN1B), and CDC73-related disorder (hyperparathyroidism - jaw tumor syndrome (HPJT)). Familial hypocalciuric hypercalcemia (FHH) caused by CASR variants is an important differential diagnosis for pHPT. In order to evaluate the contribution of hereditary causes to pHPT in patients encountered in a specialized clinic, we conducted a retrospective study on patients with pHPT that underwent germline genetic testing. We evaluated 46 patients referred to a Cancer Genetics Clinic. Reasons for referral were young age (age < 40) for 29 patients (63%), multi-gland disease for 23 patients (50%), and a positive family history of pHPT for 11 patients (24%). All 46 patients underwent genetic evaluation. A total of 11 rare variants were found (CASR (4), CDC73 (2), MEN1 (2) CDKN1B (1), and RET (2)). One MEN1 variant was classified as pathogenic, and all others were variants of uncertain significance (VUS). All patients with CASR variants had clinical features of FHH and were counselled against parathyroidectomy. Both patients with CDC73 variants were counselled about recurrence of pHPT and parathyroid cancer. Neither of the RET variants were MEN2-associated. The CDKN1B variant was regarded as a true VUS and no action was taken. In this study, genetic testing impacted clinical care in 7 (15%) patients. We suggest that all patients < 40 years of age, with multi-gland disease, single gland disease refractory to treatment, and a positive family history for pHPT or associated tumors should be considered for genetic evaluation.

[Hereditary syndromal and nonsyndromal forms of primary hyperparathyroidism]

Primary hyperparathyroidism is a common disorder of mineral homeostasis, characterized by overproduction of parathyroid hormone and upper normal or elevated calcium levels due to hyperplasia or a tumor of parathyroid gland. 90&minus;95% of cases of primary hyperparathyroidism are sporadic, while hereditary genetic forms occur in 5&ndash;10% of all cases. Primary hyperparathyroidism as the component of hereditary syndromes can present in various clinical forms (asymptomatic, symptomatic), can be associated with other endocrine or non-endocrine diseases, and require special approaches to treatment. Given that primary hyperparathyroidism is one of the most common components of these syndromes, it can be used as an important diagnostic tool in identifying affected families. This review is devoted to modern ideas about the clinical course and genetic characteristics of hereditary variants of primary hyperparathyroidism and the diagnostic and treatment algorithms recommended today. The review considers primary hyperparathyroidism as a component of hereditary syndromes including multiple endocrine neoplasias types 1, 2A and 4 and syndrome of hyperparathyroidism with a jaw tumor. Also non-syndromic hereditary forms are descripted, such as familial isolated hyperparathyroidism, familial hypocalciuric hypercalcemia, and severe neonatal primary hyperparathyroidism.

Sharing Marks: H3K4 Methylation and H2B Ubiquitination as Features of Meiotic Recombination and Transcription

Meiosis is a specialized cell division that gives raise to four haploid gametes from a single diploid cell. During meiosis, homologous recombination is crucial to ensure genetic diversity and guarantee accurate chromosome segregation. Both the formation of programmed meiotic DNA double-strand breaks (DSBs) and their repair using homologous chromosomes are essential and highly regulated pathways. Similar to other processes that take place in the context of chromatin, histone posttranslational modifications (PTMs) constitute one of the major mechanisms to regulate meiotic recombination. In this review, we focus on specific PTMs occurring in histone tails as driving forces of different molecular events, including meiotic recombination and transcription. In particular, we concentrate on the influence of H3K4me3, H2BK123ub, and their corresponding molecular machineries that write, read, and erase these histone marks. The Spp1 subunit within the Complex of Proteins Associated with Set1 (COMPASS) is a critical regulator of H3K4me3-dependent meiotic DSB formation. On the other hand, the PAF1c (RNA polymerase II associated factor 1 complex) drives the ubiquitination of H2BK123 by Rad6-Bre1. We also discuss emerging evidence obtained by cryo-electron microscopy (EM) structure determination that has provided new insights into how the "cross-talk" between these two marks is accomplished.

Prognostic role of parafibromin staining and CDC73 mutation in patients with parathyroid carcinoma: A systematic review and meta-analysis based on individual patient data

BACKGROUND AND OBJECTIVE

Parathyroid carcinoma (PC) is a rare malignant neoplasm with a relatively poor prognosis. The loss of parafibromin expression or the presence of CDC73 mutation has been found to be remarkably associated with malignancy in parathyroid tumours. However, the prognostic role of them in PC has not yet been shown due to sampling limitations. We conducted a systematic review and meta-analysis based on individual patient data to clarify the performance of parafibromin immunohistochemical staining and CDC73 gene sequencing in predicting outcomes for patients PC.

METHODS

Published studies from PubMed/MEDLINE, EMBASE, Cochrane and Scopus Databases were searched using the terms 'parafibromin', 'CDC73', 'HRPT2' and 'parathyroid' to identify eligible studies. From the included studies, the survival data of patients with PC were extracted, and a Cox proportional hazards model was used to assess hazard ratio (HR) for disease-free survival (DFS) and overall survival (OS).

RESULTS

A total of 193 patients from 9 studies were included in this survival analysis. Negative immunohistochemical staining of parafibromin was shown to be a risk factor for recurrence/metastasis (HR 2.73, P = .002) and death (HR 2.54, P = .004). Patient age ≥ 50 years was significantly related to lower OS (HR 2.37, P = .004) but not to DFS. CDC73 mutation was not statistically related to DFS or OS.

CONCLUSIONS

Negative parafibromin staining indicated a higher risk of recurrence/metastasis and mortality. The immunohistochemical staining of parafibromin seems to be more promising in predicting outcomes for patients with PC than the sequencing of CDC73.

Parathyroid cancer: An update

Parathyroid cancer (PC) is a rare malignant tumor which comprises 0.5-5% of patients with primary hyperparathyroidism (PHPT). Most of these cancers are sporadic, although it may also occur as a feature of various genetic syndromes including hyperparathyroidism-jaw tumor syndrome (HPT-JT) and multiple endocrine neoplasia (MEN) types 1 and 2A. Although PC is characterized by high levels of serum ionized calcium (Ca) and parathyroid hormone (PTH), the challenge to the clinician is to distinguish PC from the far more common entities of parathyroid adenoma (PA) or hyperplasia, as there are no specific clinical, biochemical, or radiological characteristic of PC. Complete surgical resection is the only known curative treatment for PC with the surgical approach during initial surgery strongly influencing the outcome. In order to avoid local recurrence, the lesion must be removed en-bloc with clear margins. PC has high recurrence rates of up to 50% but with favorable long-term survival rates (10-year overall survival of 60-70%) due to its slow-growing nature. Most patients die not from tumor burden directly but from uncontrolled severe hypercalcemia. In this article we have updated the information on PC by reviewing the literature over the past 10 years and summarizing the findings of the largest series published in this period.

Whole exome sequencing in familial isolated primary hyperparathyroidism

PURPOSE

Familial isolated hyperparathyroidism (FIHP) is a rare inherited disease accounting for 1% of all cases of primary hyperparathyroidism (PHPT). It is genetically heterogeneous being associated with mutations in different genes, including MEN1, CDC73, CASR, and recently GCM2. The aim of the study was to further investigate the molecular pathogenesis in Italian FIHP kindreds.

METHODS

We used whole exome sequencing (WES) in the probands of seven unrelated FIHP kindreds. We carried out a separate family-based exome analysis in a large family characterized by the co-occurrence of PHPT with multiple tumors apparently unrelated to the disease. Selected variants were also screened in 18 additional FIHP kindreds. The clinical, biochemical, and pathological characteristics of the families were also investigated.

RESULTS

Three different variants in GCM2 gene were found in two families, but only one (p.Tyr394Ser), already been shown to be pathogenic in vitro, segregated with the disease. Six probands carried seven heterozygous missense mutations segregating with the disease in the FAT3, PARK2, HDAC4, ITPR2 and TBCE genes. A genetic variant in the APC gene co-segregating with PHPT (p.Val530Ala) was detected in a family whose affected relatives had additional tumors, including colonic polyposis.

CONCLUSION

We confirm the role of GCM2 germline mutations in the pathogenesis of FIHP, although at a lower rate than in the previous WES study. Further studies are needed to establish the prevalence and the role in the predisposition to FIHP of the novel variants in additional genes.

Rare Somatic MEN1 Gene Pathogenic Variant in a Patient Affected by Atypical Parathyroid Adenoma

OBJECTIVE

Atypical parathyroid adenoma is a rare neoplasm, showing atypical histological features intermediate between classic benign adenoma and the rarest parathyroid carcinoma, whose the clinical behaviour and outcome is not yet understood or predictable. Up to date only two cases of atypical adenoma were found associated to a MEN1 syndrome, and only one was proved to carry a pathogenic variant of the MEN1 gene.

DESIGN

We report the clinical, histologic, and molecular findings of a 44-year-old woman, presenting with a histologically proved atypical parathyroid adenoma with an apparent aggressive behaviour.

METHODS AND RESULTS

CDC73 gene was screened at germline and somatic levels with no results. Whole exome sequencing performed on DNA extracted from blood leukocytes and tumour tissue revealed a somatic MEN1 gene heterozygous variant, c.912+1G > A, of the splicing donor site of exon 6. On immunohistochemistry, downregulation of the menin protein expression in the neoplastic cells was also observed.

CONCLUSIONS

We report the second case of a rare association of a somatic MEN1 gene mutation in a patient with atypical parathyroid adenoma. We suggest that MEN1 gene could be an underestimate genetic determinant of these rare histological entities, and we highlight the utility of a complete genetic screening protocol, by the use of next-generation sequencing technology in such undetermined clinical cases with no frank clinical presentation.

Parathyroid Carcinoma: An Up-to-Date Retrospective Multicentric Analysis

Parathyroid carcinoma (PC) is a rare disease responsible for about 1% of primary hyperparathyroidism (PHPT) cases. PC usually has an indolent course, tough to differentiate from the benign causes of PHPT, and the only certain diagnosis is histologic. The gold standard surgical treatment is the en bloc resection associated with the homolateral thyroid loboistmectomy. The aim of this study was to underline the main differences between PC and benign PHPT, along with gathering epidemiological knowledge relative to PC in our region. Data from the regional cancer network (Rete Oncologica del Piemonte e della Valle d'Aosta) since 2007 have been reported, including 21 patients from three hospitals (AO S. Croce e Carle of Cuneo, AOU Città della Salute of Turin, and ASL Città di Torino). The incidence of the disease, gender, age at time of diagnosis, presence of renal and bone symptoms, serum calcium and PTH levels, surgical technique performed, and percentage of recurrence were analysed. PC data were than compared with a series of patients affected by benign PHPT, referred to ASL Città di Torino, Maria Vittoria Hospital, from 2007 to 2019. A PC incidence of 0.05 cases per 100,000 inhabitants was found in our region. Benign forms occurred more frequently in females (p=0.0002), while PC equally occurred in males and females and affected younger patients (p=0.026). Serum calcium and PTH levels were significantly higher in PC patients; accordingly, typical PHPT symptoms were more frequently reported in PC than in benign PHPT. In the PC group, the en bloc resection shows a 13 times lower risk for relapse compared with all the other surgical techniques. PC is equally gender distributed, and the average patients' age is in the fifth decade of life. It is usually functioning, with greater biochemical activity and multiple symptoms. A not-radical surgical resection is associated with a higher recurrence rate. A meticulous presurgical evaluation of PHPT patients showing PC's evocative features is mandatory to obtain a complete disease extirpation.

Case report: a camouflaged parathyroid carcinoma with initial misdiagnosis

Background

Parathyroid carcinoma is a rare malignancy with an increasing incidence. Most patients are characterized by the presence of severe primary hyperparathyroidism, especially hypercalcemia, while patients with normal level of serum calcium are extremely rare. Unfortunately, patients free of hypercalcemia are usually diagnosed at a later stage and suffer from a rather poor prognosis.

Case presentation

We describe a patient diagnosed with intrathyroidal normocalcemic parathyroid carcinoma, whose preoperative ultrasonography suggests that the tumor is located inside the thyroid gland and present without obvious clinical manifestations, which makes it more challenging for diagnosis.

Conclusions

Preoperative suspicion of malignancy is of great importance for advanced management while preoperative diagnosis is rather challenging with the limited contribution of imaging examinations. Any abnormality in serum level of calcium or parathormone may help to make an initial diagnosis especially when the level is extremely high. We introduce this case of initial misdiagnosis of an intrathyroidal parathyroid carcinoma, mimicking a suspicious thyroid nodule, to focus on the possible anomalous presentations of this rare condition and on its optimal management.

Parathyroid Cancer: A Review

Parathyroid cancer is one of the rarest causes of primary hyperparathyroidism and tends to present with more severe symptoms than its more benign counterparts. This article details various aspects of the disease process, including epidemiology, clinical presentation, and a step-wise diagnostic process for parathyroid cancer. This includes laboratory assessments as well as a proposed staging system. The en bloc principle of surgical intervention is detailed, as well as the current role of adjuvant treatments. A general guide to surveillance and the natural history of the disease is also outlined.

Parathyroid Cancer: A Review

Parathyroid cancer is one of the rarest causes of primary hyperparathyroidism and tends to present with more severe symptoms than its more benign counterparts. This article details various aspects of the disease process, including epidemiology, clinical presentation, and a step-wise diagnostic process for parathyroid cancer. This includes laboratory assessments as well as a proposed staging system. The en bloc principle of surgical intervention is detailed, as well as the current role of adjuvant treatments. A general guide to surveillance and the natural history of the disease is also outlined.

Pediatric Parathyroid Carcinoma: A Case Report and Review of the Literature

Primary hyperparathyroidism (PHPT) is a rare endocrine disease in the pediatric population. Sporadic parathyroid adenomas remain the most common cause of pediatric PHPT. Parathyroid carcinoma (PC) is an extremely rare cause of pediatric PHPT. We report a 16-year-old boy presenting with a nonhealing fragility fracture of the right leg along with florid features of rickets. Examination revealed a neck mass, mimicking a goiter. Biochemical findings were consistent with PHPT. Imaging was suggestive of a right inferior parathyroid mass infiltrating the right lobe of thyroid. The patient underwent en bloc surgical excision of the parathyroid mass along with the right lobe of thyroid. Histopathology was suggestive of a PC. He achieved biochemical remission with normalization of serum calcium and parathyroid hormone levels. At follow-up, there was no biochemical or imaging evidence of recurrence or metastasis. Genetic analysis revealed heterozygous germline deletion of CDC73. An extensive literature search on PC was conducted, with an emphasis on the pediatric population. Thirteen cases of pediatric PC were identified. The median age of presentation was 13 years; there was no sex predilection. All cases were symptomatic; 31% had a visible neck mass. The median serum calcium and intact parathyroid hormone levels were 14.3 mg/dL and 2000 pg/mL, respectively. All patients underwent surgical excision, with 27% showing metastatic relapse. Our findings indicate that the preoperative features that could point toward a diagnosis of PC in a child with PHPT are a tumor size of >3 cm, thyroid infiltration on imaging, and severe hypercalcemia at presentation.