Uterine tumours are a phenotypic manifestation of the hyperparathyroidism-jaw tumour syndrome

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.

Phenotypic Profiling and Molecular Mechanisms in Hyperparathyroidism-jaw Tumor Syndrome

CONTEXT

Hyperparathyroidism-jaw tumor (HPT-JT) syndrome is a heritable form of primary hyperparathyroidism caused by germline inactivating mutations in CDC73 encoding parafibromin and is associated with an increased risk of parathyroid cancer. There is little evidence to guide the management of patients with the disease.

OBJECTIVE

(1) Characterize the natural history of HPT-JT, (2) correlate genotype and histology of parathyroid tumors with parafibromin immunostaining, (3) understand molecular changes downstream to CDC73 loss.

DESIGN

Retrospective study of patients with HPT-JT syndrome (genetically confirmed or affected first-degree relatives). Independent review of uterine tumor from 2 patients and staining for parafibromin on parathyroid tumors from 19 patients (13 adenomas, 6 carcinomas) was performed. RNA-sequencing was performed in 21 parathyroid samples (8 HPT-JT-related adenomas, 6 HPT-JT-related carcinomas, and 7 sporadic carcinomas with wild-type CDC73).

RESULTS

We identified 68 patients from 29 kindreds with HPT-JT with median age at last follow-up of 39 [interquartile range, 29-53] years. A total of 55/68 (81%) developed primary hyperparathyroidism; 17/55 (31%) had parathyroid carcinoma. Twelve of 32 (38%) females developed uterine tumors. Of the 11 patients who had surgical resection for uterine tumors, 12/24 (50%) tumors were rare mixed epithelial mesenchymal polypoid lesions. Four of 68 patients (6%) developed solid kidney tumors; 3/4 had a CDC73 variant at p.M1 residue. Parafibromin staining of parathyroid tumors did not correlate with tumor histology or genotype. RNA-sequencing showed a significant association of HPT-JT-related parathyroid tumors with transmembrane receptor protein tyrosine kinase signaling pathway, mesodermal commitment pathway, and cell-cell adhesion.

CONCLUSIONS

Multiple, recurrent atypical adenomyomatous uterine polyps appear to be enriched in women with HPT-JT and appear characteristic of the disease. Patients with CDC73 variants at p.M1 residue appear predisposed to kidney tumors.

CLINICAL TRIAL NUMBER

NCT04969926.

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.

Bilateral ossifying fibroma affecting the jaws: Literature review, rare case report

BACKGROUND

Ossifying fibroma (OF) is a benign lesion could occur in different areas of the body and contain fibers, cells and non-organic materials in non specific amounts. It is growing could be slow or rapid and according to this an array of treatment options must be considered to avoid future complications.

CASE PRESENTATION

In this article, we present a case report of a 40-year-old female patient who visited the dentist with the intention of having a normal check up. Bilateral lesion was observed in the mandible, the patient had no medical history of trauma. The lesion was removed surgically and analyzed histologically and the result was ossifying fibroma in both sides.

DISCUSSION

Ossifying fibroma is a rare tumor to be found in the oral cavity, and the family of fibro-osseous lesions (FOLs) has in general the same pathologic features and differ from each other in clinical view so the definitive diagnosis is based on mixture of all these elements. The treatment is complete surgical excision.

CONCLUSIONS AND LITERATURE REVIEW

11 cases were discovered and archived since 1968 until now, the distribution of cases is nearly equal in the oral cavity, and the infection of females is higher than males.

The spectrum of cell death in sarcoma

The balance between cell death and cell survival is a highly coordinated process by which cells break down and remove unnecessary or harmful materials in a controlled, highly regulated, and compartmentalized manner. Cell exposure to various stresses, such as oxygen starvation, a lack of nutrients, or exposure to radiation, can initiate autophagy. Autophagy is a carefully orchestrated process with multiple steps, each regulated by specific genes and proteins. Autophagy proteins impact cellular maintenance and cell fate in response to stress, and targeting this process is one of the most promising methods of anti-tumor therapy. It is currently not fully understood how autophagy affects different types of tumor cells, which makes it challenging to predict outcomes when this process is manipulated. In this review, we will explore the mechanisms of autophagy and investigate it as a potential and promising therapeutic target for aggressive sarcomas.

Parathyroid Carcinoma: Update on Pathogenesis and Therapy

Parathyroid carcinoma (PC) is a very rare endocrine cancer with aggressive behavior, a high metastatic potential, and a poor prognosis. Surgical resection of affected gland(s) and other involved structures is the elective therapy. Pre-operative and intra-operative differential diagnosis with benign parathyroid adenoma remains a challenge. The lack of a clear pre-operative diagnosis does not allow one, in many cases, to choose the correct surgical approach to malignant PC, increasing persistence, the recurrence rate, and the risk of metastases. An initial wrong diagnosis of parathyroid adenoma, with a minimally invasive parathyroidectomy, is associated with over 50% occurrence of metastases after surgery. Genetic testing could help in identifying patients at risk of congenital PC (i.e., CDC73 gene) and in driving the choice of neck surgery extension. Targeted effective treatments, other than surgery, for advanced and metastatic PC are needed. The pathogenesis of malignant parathyroid carcinogenesis is still largely unknown. In the last few years, advanced molecular techniques allowed researchers to identify various genetic abnormalities and epigenetic features characterizing PC, which could be crucial for selecting molecular targets and developing novel targeted therapeutic agents. We reviewed current findings in PC genetics, epigenetics, and proteomics and state-of-the-art therapies.

Preoperative, Intraoperative, and Postoperative Parathyroid Pathology: Clinical Pathologic Collaboration for Optimal Patient Management

Parathyroid disease typically presents with parathyroid hyperfunction as result of neoplasia or a consequence of non-neoplastic systemic disease. Given the parathyroid gland is a hormonally active organ with broad physiologic implications and serologically accessible markers for monitoring, the diagnosis of parathyroid disease is predominantly a clinical pathologic correlation. We provide the current pathological correlates of parathyroid disease and discuss preoperative, intraoperative, and postoperative pathology consultative practice for optimal patient care.

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).

A two-generation hyperparathyroidism-jaw tumor (HPT-JT) syndrome family: clinical presentations, pathological characteristics and genetic analysis: a case report

Background

Hyperparathyroidism-Jaw Tumor (HPT-JT) is caused by inactivating germline mutations of CDC73. This hereditary disease can present with a range of symptoms. Jaw ossifying fibroma (OF) is one of the most important clinical presentations, affecting 30% of HPT-JT patients. However, OF is easily confused with other fibro-osseous lesions (FOLs) of the jaw. The correct diagnosis of HPT-JT is a real challenge and must be confirmed by genetic testing.

Case presentation

A female proband and her father suffered from multiple and recurrent FOLs in the jaw. Considering well demarcated margin and heterogeneous calcified substance lying in a variable density of fibrous stroma, we reached the diagnosis of jaw OF through radiologic and microscopic analyses. Additionally, the proband presented with chronic anemia resulting from menorrhagia, as well as renal mixed epithelial and stromal tumor (MEST). Two patients both presented with no evidence of Hyperparathyroidism (HPT). A germline start codon mutation (c.1A > G) of CDC73 was identified in them. Copy number loss at the CDC73 gene locus was verified in the jaw tumor sample of the proband.

Conclusion

Regardless of whether HPT manifestations are present, patients with heritable jaw OF may be at risk for HPT-JT. Genetic testing should be adopted to confirm the diagnosis. Early recognition of HPT-JT helps to better develop tailored treatment plans and surveillance programs.

Immunohistochemical Profile of Parathyroid Tumours: A Comprehensive Review

Immunohistochemistry remains an indispensable tool in diagnostic surgical pathology. In parathyroid tumours, it has four main applications: to detect (1) loss of parafibromin; (2) other manifestations of an aberrant immunophenotype hinting towards carcinoma; (3) histogenesis of a neck mass and (4) pathogenetic events, including features of tumour microenvironment and immune landscape. Parafibromin stain is mandatory to identify the new entity of parafibromin-deficient parathyroid neoplasm, defined in the WHO classification (2022). Loss of parafibromin indicates a greater probability of malignant course and should trigger the search for inherited or somatic CDC73 mutations. Aberrant immunophenotype is characterised by a set of markers that are lost (parafibromin), down-regulated (e.g., APC protein, p27 protein, calcium-sensing receptor) or up-regulated (e.g., proliferation activity by Ki-67 exceeding 5%) in parathyroid carcinoma compared to benign parathyroid disease. Aberrant immunophenotype is not the final proof of malignancy but should prompt the search for the definitive criteria for carcinoma. Histogenetic studies can be necessary for differential diagnosis between thyroid vs. parathyroid origin of cervical or intrathyroidal mass; detection of parathyroid hormone (PTH), chromogranin A, TTF-1, calcitonin or CD56 can be helpful. Finally, immunohistochemistry is useful in pathogenetic studies due to its ability to highlight both the presence and the tissue location of certain proteins. The main markers and challenges (technological variations, heterogeneity) are discussed here in the light of the current WHO classification (2022) of parathyroid tumours.

Cancer Predisposition Genes in Adolescents and Young Adults (AYAs): a Review Paper from the Italian AYA Working Group

PURPOSE OF REVIEW

The present narrative systematic review summarizes current knowledge on germline gene mutations predisposing to solid tumors in adolescents and young adults (AYAs).

RECENT FINDINGS

AYAs with cancer represent a particular group of patients with specific challenging characteristics and yet unmet needs. A significant percentage of AYA patients carry pathogenic or likely pathogenic variants (PV/LPVs) in cancer predisposition genes. Nevertheless, knowledge on spectrum, frequency, and clinical implications of germline variants in AYAs with solid tumors is limited. The identification of PV/LPV in AYA is especially critical given the need for appropriate communicative strategies, risk of second primary cancers, need for personalized long-term surveillance, potential reproductive implications, and cascade testing of at-risk family members. Moreover, these gene alterations may potentially provide novel biomarkers and therapeutic targets that are lacking in AYA patients. Among young adults with early-onset phenotypes of malignancies typically presenting at later ages, the increased prevalence of germline PV/LPVs supports a role for genetic counseling and testing irrespective of tumor type.

Overview of the 2022 WHO Classification of Familial Endocrine Tumor Syndromes

This review of the familial tumor syndromes involving the endocrine organs is focused on discussing the main updates on the upcoming fifth edition of the WHO Classification of Endocrine and Neuroendocrine Tumors. This review emphasizes updates on histopathological and molecular genetics aspects of the most important syndromes involving the endocrine organs. We describe the newly defined Familial Cancer Syndromes as MAFA-related, MEN4, and MEN5 as well as the newly reported pathological findings in DICER1 syndrome. We also describe the updates done at the new WHO on the syndromic and non-syndromic familial thyroid diseases. We emphasize the problem of diagnostic criteria, mention the new genes that are possibly involved in this group, and at the same time, touching upon the role of some immunohistochemical studies that could support the diagnosis of some of these conditions. As pathologists play an important role in identifying tumors within a familial cancer syndrome, we highlight the most important clues for raising the suspicious of a syndrome. Finally, we highlight the challenges in defining these entities as well as determining their clinical outcome in comparison with sporadic tumors. Instead of the usual subject review, we present the highlights of the updates on familial cancer syndromes by answering select questions relevant to practicing pathologists.

Novel Glial Cells Missing-2 (GCM2) variants in parathyroid disorders

OBJECTIVE

The aim of this study was to analyze variants of the gene glial cells missing-2 (GCM2), encoding a parathyroid cell-specific transcription factor, in familial hypoparathyroidism and in familial isolated hyperparathyroidism (FIHP) without and with parathyroid carcinoma.

DESIGN

We characterized 2 families with hypoparathyroidism and 19 with FIHP in which we examined the mechanism of action of GCM2 variants.

METHODS

Leukocyte DNA of hypoparathyroid individuals was Sanger sequenced for CASR, PTH, GNA11 and GCM2 mutations. DNA of hyperparathyroid individuals underwent MEN1, CDKN1B, CDC73, CASR, RET and GCM2 sequencing. The actions of identified GCM2 variants were evaluated by in vitro functional analyses.

RESULTS

A novel homozygous p.R67C GCM2 mutation which failed to stimulate transcriptional activity in a luciferase assay was identified in affected members of two hypoparathyroid families. Oligonucleotide pull-down assay and in silico structural modeling indicated that this mutant had lost the ability to bind the consensus GCM recognition sequence of DNA. Two novel (p.I383M and p.T386S) and one previously reported (p.Y394S) heterozygous GCM2 variants that lie within a C-terminal conserved inhibitory domain were identified in three affected individuals of the hyperparathyroid families. One family member, heterozygous for p.I138M, had parathyroid carcinoma (PC), and a heterozygous p.V382M variant was found in another patient affected by sporadic PC. These variants exerted significantly enhanced in vitrotranscriptional activity, including increased stimulation of the PTH promoter.

CONCLUSIONS

We provide evidence that two novel GCM2 R67C inactivating mutations with an inability to bind DNA are causative of hypoparathyroidism. Additionally, we provide evidence that two novel GCM2 variants increased transactivation of the PTH promoter in vitro and are associated with FIHP. Furthermore, our studies suggest that activating GCM2 variants may contribute to facilitating more aggressive parathyroid disease.

Novel Glial Cells Missing-2 (GCM2) variants in parathyroid disorders

OBJECTIVE

The aim of this study was to analyze variants of the gene glial cells missing-2 (GCM2), encoding a parathyroid cell-specific transcription factor, in familial hypoparathyroidism and in familial isolated hyperparathyroidism (FIHP) without and with parathyroid carcinoma.

DESIGN

We characterized 2 families with hypoparathyroidism and 19 with FIHP in which we examined the mechanism of action of GCM2 variants.

METHODS

Leukocyte DNA of hypoparathyroid individuals was Sanger sequenced for CASR, PTH, GNA11 and GCM2 mutations. DNA of hyperparathyroid individuals underwent MEN1, CDKN1B, CDC73, CASR, RET and GCM2 sequencing. The actions of identified GCM2 variants were evaluated by in vitro functional analyses.

RESULTS

A novel homozygous p.R67C GCM2 mutation which failed to stimulate transcriptional activity in a luciferase assay was identified in affected members of two hypoparathyroid families. Oligonucleotide pull-down assay and in silico structural modeling indicated that this mutant had lost the ability to bind the consensus GCM recognition sequence of DNA. Two novel (p.I383M and p.T386S) and one previously reported (p.Y394S) heterozygous GCM2 variants that lie within a C-terminal conserved inhibitory domain were identified in three affected individuals of the hyperparathyroid families. One family member, heterozygous for p.I138M, had parathyroid carcinoma (PC), and a heterozygous p.V382M variant was found in another patient affected by sporadic PC. These variants exerted significantly enhanced in vitrotranscriptional activity, including increased stimulation of the PTH promoter.

CONCLUSIONS

We provide evidence that two novel GCM2 R67C inactivating mutations with an inability to bind DNA are causative of hypoparathyroidism. Additionally, we provide evidence that two novel GCM2 variants increased transactivation of the PTH promoter in vitro and are associated with FIHP. Furthermore, our studies suggest that activating GCM2 variants may contribute to facilitating more aggressive parathyroid disease.

A large extended family with hyperparathyroidism-jaw tumor syndrome due to deletion of the third exon of CDC73: clinical and molecular features

PURPOSE

We described the phenotype of a large 4-generation family with Hyperparathyrodism-Jaw Tumor syndrome (HPT-JT) associated with a rare deletion of exon 3 of the CDC73 gene.

METHODS

We collected medical, genetic data on 24 family members descended from a common ancestor carrying a heterozygous deletion of exon 3.

RESULTS

Thirteen carried the deletion, the penetrance was estimated at 50% at 40 years. Seven patients (39 ± 14.5 years) presented with HPT which could start at 13. Median plasmatic calcium and PTH levels were 3.13 ± 0.7 mmol/L and 115 ± 406 pg/ml, respectively. Kidney disease related to hypercalcemia were present in 57.1% of patients. All seven patients underwent surgery to remove a single parathyroid adenoma. One recurrence occurred 7 years post-surgery. No parathyroid carcinoma has been found to date. We found two atypical parathyroid adenomas. We described an additional somatic variant in exon 1 of gene CDC73 in two tumors. Jaw tumors were not necessarily associated with hyperparathyroidism, as shown in one case. Two kidney cysts were also reported. Variable phenotype expressivity was emphasized by clinical presentations in 2 monozygotic twins: acute hypercalcemia, kidney failure and ossifying fibroma in one twin, versus normocalcemic parathyroid adenoma in the other one.

CONCLUSION

We report a family carrier of a deletion of exon 3 of the CDC73 gene. This is characterized by a high level of hypercalcemia, deleterious kidney effects and atypical parathyroid adenomas without carcinomas. Onset and intensity of HPT remain unpredictable. The additional somatic mutation found in the parathyroid tumor could lead to these phenotypical variations.

The Unforeseen Diagnosis: Hyperparathyroidism-Jaw Tumour Syndrome Case Report and Review of the Literature

Hypercalcaemia and its systemic sequelae are a relatively common finding amongst patients in the field of endocrinology. Primary hyperparathyroidism, a frequent cause of hypercalcaemia, is often seen among middle-aged female patients, typically resulting from an underlying single-gland adenoma. Although patients may present with symptoms (nephrolithiasis, musculoskeletal discomfort, dehydration, or mood disturbance, to name a few), hypercalcaemia is rather frequently identified incidentally. In younger patients, a familial form of primary hyperparathyroidism must be considered, with a positive diagnosis mandating familial screening. Hyperparathyroidism-jaw tumour syndrome is one such autosomal dominant familial disorder, characterised by a mutation in the cell division cycle 73 (CDC73; also known as HRPT-2) tumour suppressor gene. This disorder is characterised by multiple pleiotropic phenomena, including recurrent primary hyperparathyroidism (and the effects of hypercalcaemia), neoplasms (such as uterine, renal, mandibular, and maxillary), and infertility. A patient not conforming to the classic candidacy for primary hyperparathyroidism requires consideration for a familial cause. Case Description. We present a rare diagnostic entity-hyperparathyroidism-jaw tumour (HPT-JT) syndrome-in a 36-year-old female with recurrent primary hyperparathyroidism, frequent nephrolithiasis, and infertility for 18 years prior to the diagnosis. We aim to promote awareness amongst medical professionals of this rare, but nonetheless essential differential diagnosis through a case report and review of the literature. Conclusion. Medical professionals must avoid diagnostic overshadowing and display a low threshold for genetic testing in younger patients with primary hyperparathyroidism. The importance of proper identification extends beyond the patient to their relatives and offspring.

Familial Hyperparathyroidism

Regulation of the serum calcium level in humans is achieved by the endocrine action of parathyroid glands working in concert with vitamin D and a set of critical target cells and tissues including osteoblasts, osteoclasts, the renal tubules, and the small intestine. The parathyroid glands, small highly vascularized endocrine organs located behind the thyroid gland, secrete parathyroid hormone (PTH) into the systemic circulation as is needed to keep the serum free calcium concentration within a tight physiologic range. Primary hyperparathyroidism (HPT), a disorder of mineral metabolism usually associated with abnormally elevated serum calcium, results from the uncontrolled release of PTH from one or several abnormal parathyroid glands. Although in the vast majority of cases HPT is a sporadic disease, it can also present as a manifestation of a familial syndrome. Many benign and malignant sporadic parathyroid neoplasms are caused by loss-of-function mutations in tumor suppressor genes that were initially identified by the study of genomic DNA from patients who developed HPT as a manifestation of an inherited syndrome. Somatic and inherited mutations in certain proto-oncogenes can also result in the development of parathyroid tumors. The clinical and genetic investigation of familial HPT in kindreds found to lack germline variants in the already known HPT-predisposition genes represents a promising future direction for the discovery of novel genes relevant to parathyroid tumor development.

Long-Term Outcomes of Parathyroidectomy in Hyperparathyroidism-Jaw Tumor Syndrome: Analysis of Five Families with CDC73 Mutations

BACKGROUND

Hyperparathyroidism-jaw tumor syndrome (HPT-JT) is a rare disease caused by CDC73 germline mutations, with familial primary hyperparathyroidism (pHPT), ossifying jaw tumors, genito-urinary neoplasms. The present study was aimed at determining the long-term postoperative outcome of parathyroidectomy in HPT-JT.

METHODS

A retrospective analysis of a single-center series of 20 patients from five unrelated HPT-JT families undergoing parathyroid surgery was performed.

RESULTS

Pathology confirmed a single-gland involvement in 95% of cases at onset. Parathyroid carcinoma occurred in three patients undergoing en-bloc parathyroidectomy and thyroid lobectomy: parathyroid benign lesions in 17 patients undergoing subtotal parathyroidectomy for evident multiglandular involvement (n = 1) or selective parathyroidectomy for single-gland involvement (n = 16), during bilateral (n = 13) or targeted unilateral neck exploration (n = 7). At a median overall follow-up of 16 years (range 2.5-42), patients with parathyroid carcinoma had a persistent/recurrent disease in 66.6%; patients with benign lesions had recurrent pHPT in 23.5% after a prolonged disease-free period; recurrent benign pHPT occurred slightly more often in cases of discordant preoperative localization (60% vs 9%; p = 0.06).

CONCLUSION

pHPT in HPT-JT is generally characterized by a benign and single-gland involvement, with a relatively increased risk of malignancy (15%). Parathyroid carcinoma needs extensive surgery because of high risk of permanent/recurrent disease (66.6%). In benign involvement, targeted unilateral exploration with selective parathyroidectomy may be effective in cases of concordant single-gland localization at preoperative localization imaging techniques. Bilateral neck exploration with subtotal parathyroidectomy might be preferred in cases of negative or discordant preoperative localization, because of the increased risk of multiglandular involvement and long-term recurrences (23.5%).

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.

Hereditary Parathyroid Disease: Sometimes Pathologists Do Not Know What They Are Missing

Parathyroid gland excision specimens are common and sometimes underestimated cases that many surgical pathologists encounter regularly. In the vast majority of cases, these will be spot diagnoses of sporadic primary parathyroid adenomas or, perhaps, hyperplasias commonly in the setting of renal failure. However, a small but significant number of parathyroid gland excisions may be due to heritable disease. In most cases, hereditary disease is suspected by the referring clinicians. Nevertheless, a subset of these are undetected which is significant, particularly in the setting of the multiple endocrine neoplasia (MEN), and the hyperparathyroidism jaw tumour (HPT-JT) syndromes. There have been recent advances in recognition of the morphological and immunohistochemical characteristics of these tumours and hyperplasias. While hereditary kindreds are over-represented at specialist referral centres, with awareness of the characteristic clinical and morphological features, the general surgical pathologist is frequently able to suggest the possibility of hereditary parathyroid disease. We therefore provide a succinct guide for pathologists to increase the recognition of hereditary parathyroid disease.

Clinical and Molecular Genetics of Primary Hyperparathyroidism

Calcium homeostasis is maintained by the actions of the parathyroid glands, which release parathyroid hormone into the systemic circulation as necessary to maintain the serum calcium concentration within a tight physiologic range. Excessive secretion of parathyroid hormone from one or more neoplastic parathyroid glands, however, causes the metabolic disease primary hyperparathyroidism (HPT) typically associated with hypercalcemia. Although the majority of cases of HPT are sporadic, it can present in the context of a familial syndrome. Mutations in the tumor suppressor genes discovered by the study of such families are now recognized to be pathogenic for many sporadic parathyroid tumors. Inherited and somatic mutations of proto-oncogenes causing parathyroid neoplasia are also known. Future investigation of somatic changes in parathyroid tumor DNA and the study of kindreds with HPT yet lacking germline mutation in the set of genes known to predispose to HPT represent two avenues likely to unmask additional novel genes relevant to parathyroid neoplasia.

Hyperparathyroidism in pregnancy

Hyperparathyroidism is a rare disease during pregnancy, which has increased risks, including miscarriage and fetal growth restriction. However, the diagnosis of hyperparathyroidism is frequently not recognised or delayed as symptoms are non-specific and calcium is not routinely measured. With a thorough medical history and clinical suspicion, early diagnosis and treatment can reduce the risk of some pregnancy complications. A 35-year-old woman presented at 13/40 with hyperemesis gravidarum. She had elevated serum calcium and a parathyroid lesion on ultrasound. She underwent a parathyroidectomy with rapid normalisation of her calcium. Histopathology confirmed a parafibromin-deficient parathyroid tumour, suggestive of hyperparathyroidism jaw tumour syndrome. At 30/40, she presented with pre-eclampsia (hypertension, hyper-reflexia, proteinuria and intrauterine growth restriction) and had a caesarean section at 30+1/40, delivering a male infant, 897 g (fifth percentile). She had a prior 12-month history of chronic constipation and nephrolithiasis but was not investigated further despite elevated calcium (2.82 mmol/L).

Gnathic Bones and Hyperparathyroidism: A Review on the Metabolic Bony Changes Affecting the Mandible and Maxilla in case of Hyperparathyroidism

Parathyroid glands secrete the parathyroid hormone that plays an essential role in bone remodeling. Excessive production of parathyroid hormone causes a common metabolic bone disorder known as hyperparathyroidism that is classified into primary, secondary, or tertiary. In hyperparathyroidism, the late bony complication is manifested as a giant cell osteolytic lesion called "brown tumor." Primary hyperparathyroidism is usually a sporadic disorder, but in minority of cases it occurs in inherited forms, and one of these forms is the hyperparathyroidism-jaw tumor syndrome, which is characterized by primary hyperparathyroidism and ossifying fibroma in the mandible and/or maxilla.

Benign polypoid adenomyomatous endometrium associated with hpt-JT syndrome: a case report

Hyperparathyroidism-jaw tumor (HPT-JT) is an autosomal dominant disorder responsible for benign and/or malignant tumors. Affected women often present life-threatening menorrhagia that leads to the identification of uterine tumors, and experience miscarriages and infertility. Overall though, fewer data concerning gynecological pathologies related to HPT-JT syndrome are available. We report the case of a 32-year-old woman with HPT-JT syndrome, referred for recurrent vaginal bleeding, with a history of repeated endometrial polyps and infertility. We also review the literature that explores medical options for these women.

Atypical presentations of parathyroid gland pathology: A pictorial review

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Adenoma, carcinoma and hyperplasia cause parathyroid gland enlargement.

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Mimics include thyroid nodules and cystic structures in the head and neck.

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Enlarged parathyroid glands can enhance variably following contrast administration.

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Hyperparathyroidism can present acutely with respiratory compromise.

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Syndromic associations.

Primary hyperparathyroidism is associated with significant morbidity and mortality. It is in this day and age, an eminently treatable condition which relies heavily on preoperative imaging to localise enlarged parathyroid glands. The imaging appearances of parathyroid gland enlargement are varied; this paper seeks to address some of its more unusual manifestations with an emphasis on its atypical enhancement patterns, mimics and associations. An enlarged glands may also present as an ‘incidentaloma’ in head and neck imaging performed for entirely different indications, or as part of sporadic or familial syndrome. Radiologists are in a good position to expedite the relevant investigations and curative treatment, and knowledge of the spectrum of imaging appearances is crucial.

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.

Coronary Heart Disease and an Incidental Parathyroid Carcinoma

A 71-year-old woman was admitted with angina pectoris. During hospitalization she developed a myocardial infarction (NSTEMI). Laboratory results revealed a mild elevated troponin and an elevated calcium level (3.35 mmol/l). Subsequently, there was a decreased phosphate (0.36 mmol/l [normal 0.81-1.62 mmol/l]) as well as 16-fold elevated serum level of parathyroid hormone (PTH, 1156 ng/l [normal 10-73 ng/l]), indicating a primary hyperparathyroidism. Sonographically a thyroidal node was detected, not clearly demarcated (TIRADS 5). FNA showed a monomorphic, partial follicular cell population with an immunohistochemical positivity for PTH. Magnetic resonance imaging (MRI) showed a 5 cm large tumor at the right caudal pole of the thyroid with compression of the dorsolateral trachea without infiltration. Surgical removal with en bloc resection of the right hemithyroid with parathyroidectomy was performed. Postoperatively the PTH level dropped to 12.1 ng/l. Pathological examination revealed a 5 cm tumor with infiltration of the thyroid and a perineural invasion. The diagnosis of a presymptomatic parathyroid carcinoma could be established. The affirmative histopathological diagnosis of a parathyroid carcinoma can be challenging and is limited to tumors with evidence of invasive growth in adjacent structures such as the thyroid and/or soft tissue, perineural spaces, angioinvasion of capsular and/or extracapsular vessels, and/or documented metastases.

Current concepts in parathyroid carcinoma: a single Centre experience

BACKGROUND

Parathyroid carcinoma is a rare neoplasm that may present sporadically or in the context of a genetic syndrome. Diagnosis and management are challenging due to the lack of clinical and pathological features that may reliably distinguish malignant from benign disease.

METHODS

From January 2013 to December 2017, from 358 consecutive patients affected by parathyroid diseases, 3 patients with parathyroid carcinoma were treated at our academic Department of General Surgery. We present our experience as illustrative of the different features of clinical presentation of parathyroid carcinoma and review its management considering the recent relevant literature.

RESULTS

Case 1: A 62-year-old man was hospitalized for left-sided palpable neck mass, hypercalcemia and elevated PTH. US-guided FNA was suspect for parathyroid carcinoma. A large cystic mass was excised in bloc with total thyroidectomy and central neck dissection. Genetic studies framed a pathologically confirmed parathyroid carcinoma within MEN1 syndrome. Case 2: A 48-year-old woman with hypothyroidism had total thyroidectomy performed for a suspect for right follicular thyroid lesion. Pathology revealed parathyroid carcinoma. Case 3: A 47 year-old man was admitted for hypercalcaemic crisis and renal failure in the context of PHPT. A lesion suggestive on US and MIBI scan for parathyroid adenoma in the right lower position was removed by mini-invasive approach. Pathology revealed parathyroid cancer and patient had completion hemythyroidectomy and central neck dissection.

CONCLUSION

Parathyroid cancer is a particularly rare endocrine malignancy, however it should be suspected in patients with primary hyperparathyroidism when severe hypercalcemia is associated to cervical mass, renal and skeletal disease. Parathyroid surgery remains the mainstay of treatment. Radical tumour resection and expedited treatment in a dedicated endocrine Center represent crucial prognostic factors.

Characterization of a novel CDC73 gene mutation in a hyperparathyrodism-jaw tumor patient affected by parathyroid carcinoma in the absence of somatic loss of heterozygosity

Hyperparathyrodism-jaw tumor (HPT-JT) syndrome is an autosomal dominant disorder. Loss of function of the cell division cycle protein 73 homolog (CDC73) gene is responsible for the syndrome. This gene encodes an ubiquitously expressed 531 amino acid protein, parafibromin, that acts as a tumor suppressor. Loss of heterozygosity (LOH) of the CDC73 locus in many HPT-JT associated parathyroid tumors from patients with germline mutation is in accordance with Knudson's "two-hit" model for hereditary cancer. A 41-year-old man with mandible ossifying fibroma suffered from severe hypercalcemia due to parathyroid carcinoma (PC). Genetic analysis was performed to evaluate germinal and somatic CDC73 gene mutation as well as real-time qRT-PCR to quantify CDC73 mRNA, miR-155 and miR-664 expression levels. Immunohistochemistry and Western blotting (WB) assay were carried out to evaluate parafibromin protein expression. A novel heterozygous nonsense mutation, c.191-192 delT, was identified in the CDC73 gene. No CDC73 LOH was found in PC tissue, nor any differences in expression levels for CDC73 gene, miR-155 and miR-664 between PC and parathyroid adenoma control tissues. On the contrary, both immunohistochemistry and WB assay showed an approximate 90% reduction of parafibromin protein expression in PC. In conclusion, this study describes a novel germinal mutation, c.191-192 delT, in the CDC73 gene. Despite normal CDC73 gene expression, we found a significant decrease in parafibromin. We hypothesize that a gene silencing mechanism, possibly induced by microRNA, could play a role in determining somatic post-transcriptional inactivation of the wild type CDC73 allele.

OVARIAN GRANULOSA CELL TUMOR IN A PATIENT WITH A PATHOGENIC VARIANT IN THE CDC73 GENE (HYPERPARATHYROIDISM-JAW TUMOR SYNDROME)

Objective

To report a patient with the hyperparathyroidism-jaw tumor syndrome (HPT-JT) who was found to have a rare ovarian tumor (granulosa cell tumor [GCT]). HPT-JT is caused by pathogenic variants in the CDC73 gene and results in primary hyperparathyroidism (PHPT), benign fibro-osseous jaw tumors, benign or malignant renal tumors and cysts, and benign or malignant uterine tumors. We believe this is the first reported case of HPT-JT and GCT.

Methods

The patient was a 31-year-old woman with abdominal pain who was found to have adult GCT. Her history was significant for a single gland parathyroidectomy at age 23 for PHPT. Her mother also had PHPT with 1-gland removal, as well as a history of renal cysts. Because of the personal and familial history of PHPT, she underwent germline sequencing of genes associated with PHPT including CASR, CDC73, CDKN1B, MEN1 and RET.

Results

Genetic testing revealed a CDC73 gene pathogenic variant (c.687_688dupAG) which creates a premature translational stop signal causing loss-of-function.

Conclusion

We report a case of ovarian GCT in a young patient with primary hyperparathyroidism and a CDC73 gene mutation. Ovarian granulosa cell tumor may be another CDC73-related tumor.

New Concepts About Familial Isolated Hyperparathyroidism

CONTEXT

Familial isolated hyperparathyroidism (FIHP) is defined as familial primary hyperparathyroidism (FH) without a characteristic extra-parathyroidal feature of a more complex hyperparathyroid syndrome. During 80 years, new concepts of FIHP have been developed within this definition. FIHP has been difficult to study due to small kindreds and mildly symptomatic cases.

EVIDENCE ACQUISITION

Searches were through PubMed for FIHP, other FH syndromes, and the gene(s) mutated in each.

EVIDENCE SYNTHESIS

Within its definition, the current concept of FIHP has clinical and mutational components. It can include incomplete expressions of MEN1 FHH, or HPT-JT or their mutations. Newest concepts of FIHP focus upon kindreds without mutation of either the MEN1, CASR, or CDC73 gene; 17% have germline activating mutation of the gene for the GCM2 transcription factor. Other genes for FIHP will probably be identified shortly. The FIHP kindreds with or without GCM2 mutation contain a median of only 2 cases of PHPT. The small kindred size in both subgroups of FIHP is probably caused low rate of screening among relatives. PHPT in FIHP with GCM2 mutation seems similar to PHPT in MEN1. Persons with FIHP and GCM2 mutation present as adults with mild hypercalcemia and multiple parathyroid tumors.

CONCLUSIONS

The current concept of FIHP led to a focus on small kindreds without mutation of MEN1, CASR, or CDC73. These assisted in the identification of germline activating GCM2 mutations in 17%. There is a need for clinical and mutational characterization in more cases to determine any unique clinical features of FIHP, either with or without mutation of GCM2.

Inherited Deletion of 1q, Hyperparathyroidism and Signs of Y-chromosomal Influence in a Patient with Turner Syndrome

We report a detailed phenotypic, cytogenetic and molecular characterization of a patient prenatally diagnosed with Turner syndrome (TS). In addition to having typical TS clinical characteristics including webbed neck, high arched palate and coarctation of the aorta, the patient had features less frequently seen in TS. These included recurrent parathyroid adenomas, growth along the 75^th-90^th centiles on the TS height curve despite minimal treatment with growth hormone, behavioral problems and evidence of gonadal dysgenesis with testicular-like structures, such as seminiferous tubules lined by Sertoli cells and a contiguous nodule of Leydig cells. While fluorescence in situ hybridization (FISH) failed to detect Y-chromosome material in gonadal tissue or blood samples, chromosomal microarray analysis (CMA) confirmed X monosomy and a 4.69 Mb copy number loss on 1q31.2q31.3 (bp 192,715,814 to 197,401,180). This region contains the CDC73 gene which has been associated with hyperparathyroidism-jaw tumor syndrome, features of which include recurrent, functional parathyroid adenomas and behavioral issues. This case illustrates how atypical features in a TS patient, such as robust growth and recurrent parathyroid adenomas, may suggest an underlying molecular etiology that should be explored by additional genetic diagnostic modalities. It is therefore appropriate in such cases to conduct further genetic testing, such as CMA and FISH, to explore other diagnostic possibilities and possibly prevent further complications.

Overview of Genetically Determined Diseases/Multiple Endocrine Neoplasia Syndromes Predisposing to Endocrine Tumors

In this chapter, we present an overview of multiple endocrine neoplasia syndromes including their most important clinical and molecular features. Multiple endocrine neoplasia type 1 and 2 syndromes (MEN1 and MEN2) are discussed in detail. Syndromes that are presented in other chapters are only briefly mentioned. We discuss the relevance of germline gene alterations in apparently sporadic endocrine tumors, e.g., medullary thyroid cancer, primary hyperparathyroidism, and neuroendocrine tumors. McCune-Albright syndrome that only exists in non-hereditary, sporadic forms is also discussed in detail, as tumors of several endocrine organs can develop in the same individual.

Clinical Features, Treatment, and Surveillance of Hyperparathyroidism-Jaw Tumor Syndrome: An Up-to-Date and Review of the Literature

Hyperparathyroidism-jaw tumor (HPT-JT) syndrome is an autosomal dominant disorder characterized by parathyroid tumors in association with fibro-osseous jaw tumors and uterine and renal lesions. HPT-JT syndrome is caused by germline mutations of the cell division cycle 73 (CDC73) gene that encodes the parafibromin, a 531-amino acid protein with antiproliferative activity. Primary hyperparathyroidism is the main finding of HPT-JT syndrome, usually caused by a single-gland parathyroid involvement (80% of cases), at variance with other variants of hereditary hyperparathyroidism, in which a multiglandular involvement is more frequent. Moreover, parathyroid carcinoma may occur in approximately 20% of cases. Surgery is the treatment of choice for primary hyperparathyroidism, but the extent of surgery remains controversial, varying between bilateral neck and focused exploration, with subtotal or limited parathyroidectomy. Recently, more limited approaches and parathyroid excisions have been suggested in order to decrease the risk of permanent hypoparathyroidism, the main surgical morbidity following more extensive surgical approaches. Ossifying fibromas of the mandible or maxilla may present only in a minority of cases and, even if benign, they should be surgically treated to avoid tumor growth and subsequent functional limitations. Benign and malignant uterine involvement (including leiomyomas, endometrial hyperplasia, adenomyosis, multiple adenomyomatous polyps, and adenosarcomas) is the second most common clinical feature of the syndrome, affecting more than 50% of CDC73-carrier women. Genetic testing should be performed in all family members of affected individuals, in young patients undergoing surgery for primary hyperparathyroidism, or in presence of other associated tumors, allowing early diagnosis and prompt treatment with more tailored surgery. Moreover, CDC73 mutation carriers should be also periodically screened for primary hyperparathyroidism and the other associated tumors. The present review was aimed to summarize the main clinical features of HPT-JT syndrome, focusing on genetic screening and surgical treatment, and to revise the available literature.

Evolution of Our Understanding of the Hyperparathyroid Syndromes: A Historical Perspective

We review advancing and overlapping stages for our understanding of the expressions of six hyperparathyroid (HPT) syndromes: multiple endocrine neoplasia type 1 (MEN1) or type 4, multiple endocrine neoplasia type 2A (MEN2A), hyperparathyroidism-jaw tumor syndrome, familial hypocalciuric hypercalcemia, neonatal severe primary hyperparathyroidism, and familial isolated hyperparathyroidism. During stage 1 (1903 to 1967), the introduction of robust measurement of serum calcium was a milestone that uncovered hypercalcemia as the first sign of dysfunction in many HPT subjects, and inheritability was reported in each syndrome. The earliest reports of HPT syndromes were biased toward severe or striking manifestations. During stage 2 (1959 to 1985), the early formulations of a syndrome were improved. Radioimmunoassays (parathyroid hormone [PTH], gastrin, insulin, prolactin, calcitonin) were breakthroughs. They could identify a syndrome carrier, indicate an emerging tumor, characterize a tumor, or monitor a tumor. During stage 3 (1981 to 2006), the assembly of many cases enabled recognition of further details. For example, hormone non-secreting skin lesions were discovered in MEN1 and MEN2A. During stage 4 (1985 to the present), new genomic tools were a revolution for gene identification. Four principal genes ("principal" implies mutated or deleted in 50% or more probands for its syndrome) (MEN1, RET, CASR, CDC73) were identified for five syndromes. During stage 5 (1993 to the present), seven syndromal genes other than a principal gene were identified (CDKN1B, CDKN2B, CDKN2C, CDKN1A, GNA11, AP2S1, GCM2). Identification of AP2S1 and GCM2 became possible because of whole-exome sequencing. During stages 4 and 5, the newly identified genes enabled many studies, including robust assignment of the carriers and non-carriers of a mutation. Furthermore, molecular pathways of RET and the calcium-sensing receptor were elaborated, thereby facilitating developments in pharmacotherapy. Current findings hold the promise that more genes for HPT syndromes will be identified and studied in the near future. © 2018 American Society for Bone and Mineral Research.

HIGH RISK OF PARATHYROID CARCINOMA AND GENETIC SCREENING IN THE FIRST DIAGNOSED ROMANIAN FAMILY WITH HYPERPARATHYROIDISM-JAW TUMOR SYNDROME AND A GERMLINE MUTATION OF THE CDC73 GENE

Context

Hyperparathyroidism-jaw tumour (HPT-JT) syndrome is a rare autosomal dominant cause of familial hyperparathyroidism associated with ossifying fibromas (OF) of the maxillofacial bones and increased risk of parathyroid carcinoma, caused by inactivating germline mutation of the cell division cycle 73 (CDC73) gene.

Objective

To report the first Romanian family with HPT-JT and genetic screening of CDC73 gene.

Subjects and Methods

Mutational analysis of the CDC73 gene and genetic screening of the family of a proband with HPT-JT. Histological diagnosis of parathyroid tumors (WHO criteria) and immunohistochemistry (parafibromin) were performed.

Results

Three of the six screened family members had evidence of PHPT and surgically proven parathyroid tumours. Two of the three affected members had parathyroid carcinomas and one had two parathyroid adenomas. Genetic screening of CDC73 gene revealed that 4 of 6 patients showed a heterozygous germline deletion of one nucleotide: c.128-IVS1+1 delG. All the three affected patients, resulted to be carriers of the CDC73 mutation, but each one bearing a different CDC73 polymorphism.

Conclusions

We identified a new CDC73 germline mutation in a Romanian family of HPT-JT. Analysis of clinical phenotypes in the four mutated individuals confirmed the incomplete penetrance and the variable clinical expression of the disease.

Molecular pathogenesis of parathyroid tumours

Parathyroid tumors represent an elusive endocrine neoplasia, which lead to primary hyperparathyroidism, pHPT, a common endocrine calcium disorder characterized by hypercalcemia and normal-high parathormone secretion. Parathyroid tumours are benign adenomas or multiple glands hyperplasia in the vast majority (>99% of cases), while malignant neoplasms are rare (less than 1%). Despite pHPT is a common disorder, our knowledge about the genetic predisposition and molecular pathophysiology is limited to the familial syndromic forms of parathyroid tumour, that, however, represent not more than the 10% of all the cases; instead, the pathophysiology of sporadic forms remains an open field, although data about epigenetic mechanisms or private genes have been supposed. Here we present an overview of more recent acquisitions about the genetic causes along with their molecular mechanisms of benign, but also, malignant parathyroid tumours either in sporadic and familial presentation.

CDC73 Germline Mutation in a Family With Mixed Epithelial and Stromal Tumors

OBJECTIVE

To describe a family in which 3 members presented with mixed epithelial tumor of the kidney (MEST) and were found to possess a germline mutation in CDC73, a gene which is associated with hyperparathyroidism-jaw tumor syndrome (HPT-JT).

MATERIALS AND METHODS

Blood and tumor DNA from three family members who presented with a primary diagnosis of MEST was subjected to targeted gene sequencing to identify potential genetic components.

RESULTS

A germline start codon mutation (p.M1I) in CDC73 was identified in all 3 family members who presented with MEST and 2 tumors from 1 patient demonstrated somatic copy-neutral loss of heterozygosity. Patients presented with no evidence of hyperparathyroidism or jaw tumors, but both female patients had hysterectomies at an early age due to excessive bleeding and numerous fibroids, which is common in HPT-JT. A germline p.M1I mutation has been previously reported in a family with clinical features of HPT-JT.

CONCLUSION

Patients with MEST may be at risk for HPT-JT and CDC73 germline mutation testing of MEST patients should be considered.

Multiple Endocrine Neoplasia and Hyperparathyroid-Jaw Tumor Syndromes: Clinical Features, Genetics, and Surveillance Recommendations in Childhood

Children and adolescents who present with neuroendocrine tumors are at extremely high likelihood of having an underlying germline predisposition for the multiple endocrine neoplasia (MEN) syndromes, including MEN1, MEN2A and MEN2B, MEN4, and hyperparathyroid-jaw tumor (HPT-JT) syndromes. Each of these autosomal dominant syndromes results from a specific germline mutation in unique genes: MEN1 is due to pathogenic MEN1 variants (11q13), MEN2A and MEN2B are due to pathogenic RET variants (10q11.21), MEN4 is due to pathogenic CDKN1B variants (12p13.1), and the HPT-JT syndrome is due to pathogenic CDC73 variants (1q25). Although each of these genetic syndromes share the presence of neuroendocrine tumors, each syndrome has a slightly different tumor spectrum with specific surveillance recommendations based upon tumor penetrance, including the age and location for which specific tumor types most commonly present. Although the recommended surveillance strategies for each syndrome contain similar approaches, important differences do exist among them. Therefore, it is important for caregivers of children and adolescents with these syndromes to become familiar with the unique diagnostic criteria for each syndrome, and also to be aware of the specific tumor screening and prophylactic surgery recommendations for each syndrome. Clin Cancer Res; 23(13); e123-e32. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

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

Parathyroid carcinoma (PC) may occur as part of a complex hereditary syndrome or an isolated (i.e., non‐syndromic) non‐hereditary (i.e., sporadic) endocrinopathy. Studies of hereditary and syndromic forms of PC, which include the hyperparathyroidism‐jaw tumor syndrome (HPT‐JT), multiple endocrine neoplasia types 1 and 2 (MEN1 and MEN2), and familial isolated primary hyperparathyroidism (FIHP), have revealed some genetic mechanisms underlying PC. Thus, cell division cycle 73 (CDC73) germline mutations cause HPT‐JT, and CDC73 mutations occur in 70% of sporadic PC, but in only ∼2% of parathyroid adenomas. Moreover, CDC73 germline mutations occur in 20%–40% of patients with sporadic PC and may reveal unrecognized HPT‐JT. This indicates that CDC73 mutations are major driver mutations in the etiology of PCs. However, there is no genotype–phenotype correlation and some CDC73 mutations (e.g., c.679_680insAG) have been reported in patients with sporadic PC, HPT‐JT, or FIHP. Other genes involved in sporadic PC include germline MEN1 and rearranged during transfection (RET) mutations and somatic alterations of the retinoblastoma 1 (RB1) and tumor protein P53 (TP53) genes, as well as epigenetic modifications including DNA methylation and histone modifications, and microRNA misregulation. This review summarizes the genetics and epigenetics of the familial syndromic and non‐syndromic (sporadic) forms of PC.

Large intragenic deletion of CDC73 (exons 4-10) in a three-generation hyperparathyroidism-jaw tumor (HPT-JT) syndrome family

Background

Inactivating mutations of CDC73 cause Hyperparathyroidism-Jaw Tumour syndrome (HPT-JT), Familial Isolated Hyperparathyroidism (FIHP) and sporadic parathyroid carcinoma. We conducted CDC73 mutation analysis in an HPT-JT family and confirm carrier status of the proband’s daughter.

Methods

The proband had primary hyperparathyroidism (parathyroid carcinoma) and uterine leiomyomata. Her father and daughter had hyperparathyroidism (parathyroid adenoma) but no other manifestations of HPT-JT. CDC73 mutation analysis (sequencing of all 17 exons) and whole-genome copy number variation (CNV) analysis was done on leukocyte DNA of the three affecteds as well as the proband’s unaffected sister.

Results

A novel deletion of exons 4 to 10 of CDC73 was detected by CNV analysis in the three affecteds. A novel insertion in the 5’UTR (c.-4_-11insG) that co-segregated with the deletion was identified. By in vitro assay the 5’UTR insertion was shown to significantly impair the expression of the parafibromin protein. Screening for the mutated CDC73 confirmed carrier status in the proband’s daughter and the biochemistry and ultrasonography led to pre-emptive surgery and resolution of the hyperparathyroidism.

Conclusions

A novel gross deletion mutation in CDC73 was identified in a three-generation HPT-JT family emphasizing the importance of including screening for large deletions in the molecular diagnostic protocol.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-017-0445-0) contains supplementary material, which is available to authorized users.

Genetics of Hyperparathyroidism, Including Parathyroid Cancer

Primary hyperparathyroidism (HPT) is a metabolic disease caused by the excessive secretion of parathyroid hormone from 1 or more neoplastic parathyroid glands. HPT is largely sporadic, but it can be associated with a familial syndrome. The study of such families led to the discovery of tumor suppressor genes whose loss of function is now recognized to underlie the development of many sporadic parathyroid tumors. Heritable and acquired oncogenes causing parathyroid neoplasia are also known. Studies of somatic changes in parathyroid tumor DNA and investigation of kindreds with unexplained familial HPT promise to unmask more genes relevant to parathyroid neoplasia.

Osteoblast-specific deletion of Hrpt2/Cdc73 results in high bone mass and increased bone turnover

Inactivating mutations that lead to loss of heterozygosity within the HRPT2/Cdc73 gene are directly linked to the development of primary hyperparathyroidism, parathyroid adenomas, and ossifying fibromas of the jaw (HPT-JT). The protein product of the Cdc73 gene, parafibromin, is a core member of the polymerase-associated factors (PAF) complex, which coordinates epigenetic modifiers and transcriptional machinery to control gene expression. We conditionally deleted Cdc73 within mesenchymal progenitors or within mature osteoblasts and osteocytes to determine the consequences of parafibromin loss within the mesenchymal lineage. Homozygous deletion of Cdc73 via the Dermo1-Cre driver resulted in embryos which lacked mesenchymal organ development of internal organs, including the heart and fetal liver. Immunohistochemical detection of cleaved caspase-3 revealed extensive apoptosis within the progenitor pools of developing organs. Unexpectedly, when Cdc73 was homozygously deleted within mature osteoblasts and osteocytes (via the Ocn-Cre driver), the mice had a normal life span but increased cortical and trabecular bone. OCN-Cre;Cdc73^flox/flox bones displayed large cortical pores actively undergoing bone remodeling. Additionally the cortical bone of OCN-Cre;Cdc73^flox/flox femurs contained osteocytes with marked amounts of cytoplasmic RNA and a high rate of apoptosis. Transcriptional analysis via RNA-seq within OCN-Cre;Cdc73^flox/flox osteoblasts showed that loss of Cdc73 led to a derepression of osteoblast-specific genes, specifically those for collagen and other bone matrix proteins. These results aid in our understanding of the role parafibromin plays within transcriptional regulation, terminal differentiation, and bone homeostasis.

Mice deleted for cell division cycle 73 gene develop parathyroid and uterine tumours: model for the hyperparathyroidism-jaw tumour syndrome

The hyperparathyroidism-jaw tumour (HPT-JT) syndrome is an autosomal dominant disorder characterized by occurrence of parathyroid tumours, often atypical adenomas and carcinomas, ossifying jaw fibromas, renal tumours and uterine benign and malignant neoplasms. HPT-JT is caused by mutations of the cell division cycle 73 (CDC73) gene, located on chromosome 1q31.2 and encodes a 531 amino acid protein, parafibromin. To facilitate in vivo studies of Cdc73 in tumourigenesis we generated conventional (Cdc73^+/-) and conditional parathyroid-specific (Cdc73^+/L/PTH-Cre and Cdc73^L/L/PTH-Cre) mouse models. Mice were aged to 18-21 months and studied for survival, tumour development and proliferation, and serum biochemistry, and compared to age-matched wild-type (Cdc73^+/+ and Cdc73^+/+/PTH-Cre) littermates. Survival of Cdc73^+/- mice, when compared to Cdc73^+/+ mice was reduced (Cdc73^+/-=80%; Cdc73^+/+=90% at 18 months of age, P<0.05). Cdc73^+/-, Cdc73^+/L/PTH-Cre and Cdc73^L/L/PTH-Cre mice developed parathyroid tumours, which had nuclear pleomorphism, fibrous septation and increased galectin-3 expression, consistent with atypical parathyroid adenomas, from 9 months of age. Parathyroid tumours in Cdc73^+/-, Cdc73^+/L/PTH-Cre and Cdc73^L/L/PTH-Cre mice had significantly increased proliferation, with rates >fourfold higher than that in parathyroid glands of wild-type littermates (P<0.0001). Cdc73^+/-, Cdc73^+/L/PTH-Cre and Cdc73^L/L/PTH-Cre mice had higher mean serum calcium concentrations than wild-type littermates, and Cdc73^+/- mice also had increased mean serum parathyroid hormone (PTH) concentrations. Parathyroid tumour development, and elevations in serum calcium and PTH, were similar in males and females. Cdc73^+/- mice did not develop bone or renal tumours but female Cdc73^+/- mice, at 18 months of age, had uterine neoplasms comprising squamous metaplasia, adenofibroma and adenomyoma. Uterine neoplasms, myometria and jaw bones of Cdc73^+/- mice had increased proliferation rates that were 2-fold higher than in Cdc73^+/+ mice (P<0.05). Thus, our studies, which have established mouse models for parathyroid tumours and uterine neoplasms that develop in the HPT-JT syndrome, provide in vivo models for future studies of these tumours.

Genetics of parathyroid tumours

Primary hyperparathyroidism (PHPT), due to parathyroid tumours, may occur as part of a complex syndrome or as an isolated (nonsyndromic) disorder, and both forms can occur as familial (i.e. hereditary) or nonfamilial (i.e. sporadic) disease. Syndromic PHPT includes multiple endocrine neoplasia (MEN) types 1 to 4 (MEN1 to MEN4) and the hyperparathyroidism-jaw tumour (HPT-JT) syndrome. Syndromic and hereditary PHPT are often associated with multiple parathyroid tumours, in contrast to sporadic PHPT, in which single parathyroid adenomas are more common. In addition, parathyroid carcinomas may occur in ~15% of patients with the HPT-JT syndrome. MEN1 is caused by abnormalities of the MEN1 gene which encodes a tumour suppressor; MEN2 and MEN3 are due to mutations of the rearranged during transfection (RET) proto-oncogene, which encodes a tyrosine kinase receptor; MEN4 is due to mutations of a cyclin-dependent kinase inhibitor (CDNK1B); and HPT-JT is due to mutations of cell division cycle 73 (CDC73), which encodes parafibromin. Nonsyndromic PHPT, which may be hereditary and referred to as familial isolated hyperparathyroidism, may also be due to MEN1, CDC73 or calcium-sensing receptor (CASR) mutations. In addition, ~10% of patients presenting below the age of 45 years with nonsyndromic, sporadic PHPT may have MEN1, CDC73 or CASR mutations, and overall more than 10% of patients with PHPT will have a mutation in one of 11 genes. Genetic testing is available and of value in the clinical setting, as it helps in making the correct diagnosis and planning the management of these complex disorders associated with parathyroid tumours.

Hyperparathyroidism jaw tumour syndrome: a pictoral review

Hyperparathyroidism jaw tumour syndrome is a rare autosomal dominant inherited endocrine neoplasia syndrome, which predisposes carriers to develop a triad of multiple ossifying fibromas of the maxilla and mandible, parathyroid adenomas and carcinomas (with consequent hyperparathyroidism) as well as renal and uterine tumours. The prevalence of this condition is unknown. Patients typically present initially with symptoms and signs of a jaw tumour. A high index of suspicion is required for the underlying diagnosis to be recognised, enabling appropriate management of jaw lesions, treatment of hyperparathyroidism, if present, as well as early detection of malignant disease and screening of family members.

TEACHING POINTS

• HPT-JT is a rare autosomal dominant inherited endocrine neoplasia syndrome. • HPT-JT causes facial disfigurement, morbidity secondary to hyperparathyroidism and malignancy. • Patients can present with ossifying fibromas of the jaw, hypercalcaemia or malignancy. • A high index of suspicion is required for the underlying diagnosis to be recognised. • Management involves screening of family members.

Hyperparathyroidism-jaw Tumor Syndrome: An Overlooked Cause of Severe Hypercalcemia

Ossifying fibromas of the maxillofacial bones are an uncommon form of benign neoplasm usually treated by surgical excision. Up to 30% of patients with hyperparathyroidism-jaw tumor syndrome, a rare form of multiple endocrine neoplasia resulting from autosomal dominant inactivating mutation of the Hrpt2 tumor suppressor gene, initially present with ossifying fibromas. Coincident hypercalcemia because of the presence of parathyroid adenoma is common in these patients, of whom 15% may have or may develop parathyroid carcinoma. The authors present a case of severe postsurgical hypercalcemia after removal of a large maxillary ossifying fibroma in a patient with previously unrecognized hyperparathyroidism-jaw tumor AU3 syndrome.