A novel mutation in the upstream open reading frame of the CDKN1B gene causes a MEN4 phenotype.

The CDKN1B gene encodes the cyclin-dependent kinase inhibitor p27(KIP1), an atypical tumor suppressor playing a key role in cell cycle regulation, cell proliferation, and differentiation. Impaired p27(KIP1) expression and/or localization are often observed in tumor cells, further confirming its central role in regulating the cell cycle. Recently, germline mutations in CDKN1B have been associated with the inherited multiple endocrine neoplasia syndrome type 4, an autosomal dominant syndrome characterized by varying combinations of tumors affecting at least two endocrine organs. In this study we identified a 4-bp deletion in a highly conserved regulatory upstream ORF (uORF) in the 5'UTR of the CDKN1B gene in a patient with a pituitary adenoma and a well-differentiated pancreatic neoplasm. This deletion causes the shift of the uORF termination codon with the consequent lengthening of the uORF-encoded peptide and the drastic shortening of the intercistronic space. Our data on the immunohistochemical analysis of the patient's pancreatic lesion, functional studies based on dual-luciferase assays, site-directed mutagenesis, and on polysome profiling show a negative influence of this deletion on the translation reinitiation at the CDKN1B starting site, with a consequent reduction in p27(KIP1) expression. Our findings demonstrate that, in addition to the previously described mechanisms leading to reduced p27(KIP1) activity, such as degradation via the ubiquitin/proteasome pathway or non-covalent sequestration, p27(KIP1) activity can also be modulated by an uORF and mutations affecting uORF could change p27(KIP1) expression. This study adds the CDKN1B gene to the short list of genes for which mutations that either create, delete, or severely modify their regulatory uORFs have been associated with human diseases.

First evidence of TRPV5 and TRPV6 channels in human parathyroid glands: possible involvement in neoplastic transformation.

The parathyroid glands play an overall regulatory role in the systemic calcium (Ca(2+)) homeostasis. The purpose of the present study was to demonstrate the presence of the Ca(2+) channels transient receptor potential vanilloid (TRPV) 5 and TRPV6 in human parathyroid glands. Semi-quantitative and quantitative PCR was carried out to evaluate the presence of TRPV5 and TRPV6 mRNAs in sporadic parathyroid adenomas and normal parathyroid glands. Western blot and immunocytochemical assays were used to assess protein expression, cellular localization and time expression in primary cultures from human parathyroid adenoma. TRPV5 and TRPV6 transcripts were then identified both in normal and pathological tissues. Predominant immunoreactive bands were detected at 75-80 kD for both vanilloid channels. These channels co-localized with the calcium-sensing receptor (CASR) on the membrane surface, but immunoreactivity was also detected in the cytosol and around the nuclei. Our data showed that western blotting recorded an increase of protein expression of both channels in adenoma samples compared with normal glands suggesting a potential relation with the cell calcium signalling pathway and the pathological processes of these glands.

Whole-exome sequencing of atypical parathyroid tumors detects novel and common genes linked to parathyroid tumorigenesis.

CONTEXT: Atypical parathyroid tumor (APT) represents a neoplasm characterized by histological features typical of parathyroid carcinoma (PC) but lacking local infiltration and/or distant metastasis, leading to uncertainty regarding its malignant potential. OBJECTIVE: To characterize the molecular landscape and deregulated pathways in APT. METHODS: Whole exome sequencing (WES) was conducted on 16 APTs. DNA from tumors and matched peripheral blood underwent WES using Illumina HiSeq3000. RESULTS: A total of 192 nonsynonymous variants were identified. The median number of protein-altering mutations was 9. The most frequently mutated genes included BCOR, CLMN, EZH1, JAM2, KRTAP13-3, MUC16, MUC19, and OR1S1. Seventeen mutated genes belong to the Cancer Gene Census list. The most consistent hub genes identified through STRING network analysis were ATM, COL4A5, EZH2, MED12, MEN1, MTOR, PI3, PIK3CA, PIK3CB, and UBR5. Deregulated pathways included the PI3 K/AKT/mTOR pathway, Wnt signaling, and extracellular matrix organization. Variants in genes such as MEN1, CDC73, EZH2, PIK3CA, and MTOR, previously reported as established or putative/candidate driver genes in benign adenoma (PA) and/or PC, were also identified in APT. CONCLUSIONS: APT does not appear to have a specific molecular signature but shares genomic alterations with both PA and PC. The incidence of CDC73 mutations is low, and it remains unclear whether these mutations are associated with a higher risk of recurrence. Our study confirms that PI3 K/AKT/mTOR and Wnt signaling represents the pivotal pathways in parathyroid tumorigenesis and also revealed mutations in key epigenetic modifier genes (BCOR, KDM2A, MBD4, and EZH2) involved in chromatin remodeling, DNA, and histone methylation.

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.

Cutaneous lesions and other non-endocrine manifestations of Multiple Endocrine Neoplasia type 1 syndrome.

Background: Multiple Endocrine Neoplasia type 1 is a rare genetic syndrome mainly caused by mutations of MEN1 gene and characterized by a combination of several endocrine and non-endocrine manifestations. The objective of this study was to describe cutaneous lesions and other non-endocrine manifestations of MEN1 in a cohort of patients with familial (F) and sporadic (S) MEN1, compare the prevalence of these manifestations between the two cohorts, and investigate the correlation with MEN1 mutation status. Methods: We collected phenotypic and genotypic data of 185 patients with F-MEN1 and S-MEN1 followed from 1997 to 2022. The associations between F-MEN1 and S-MEN1 or MEN1 mutation-positive and mutation-negative patients and non-endocrine manifestations were determined using chi-square or Fisher's exact tests or multivariate exact logistic regression analyses. Results: The prevalence of angiofibromas was significantly higher in F-MEN1 than in S-MEN1 in both the whole (p < 0.001) and index case (p = 0.003) cohorts. The prevalence of lipomas was also significantly higher in F-MEN1 than in S-MEN1 (p = 0.009) and in MEN1 mutation-positive than in MEN1 mutation-negative (p = 0.01) index cases. In the whole cohort, the prevalence of lipomas was significantly higher in MEN1 mutation-positive compared to MEN1 mutation-negative patients (OR = 2.7, p = 0.02) and in F-MEN1 than in S-MEN1 (p = 0.03), only after adjustment for age. No significant differences were observed for the other non-endocrine manifestations between the two cohorts. Hibernoma and collagenoma were each present in one patient (0.5%) and meningioma and neuroblastoma in 2.7% and 0.5%, respectively. Gastric leiomyoma was present in 1.1% of the patients and uterine leiomyoma in 14% of women. Thyroid cancer, breast cancer, lung cancer, basal cell carcinoma, melanoma, and colorectal cancer were present in 4.9%, 2.7%, 1.6%, 1.6%, 2.2%, and 0.5% of the whole series, respectively. Conclusions: We found a significantly higher prevalence of angiofibromas and lipomas in F-MEN1 compared with S-MEN1 and in MEN1 mutation-positive compared to MEN1 mutation-negative patients. In patients with one major endocrine manifestation of MEN1 , the presence of cutaneous lesions might suggest the diagnosis of MEN1 and a possible indication for genetic screening.

Functioning glucagonoma associated with primary hyperparathyroidism: multiple endocrine neoplasia type 1 or incidental association?

BACKGROUND: Diagnosis of multiple endocrine neoplasia type 1 (MEN1) is commonly based on clinical criteria, and confirmed by genetic testing. In patients without known MEN1-related germline mutations, the possibility of a casual association between two or more endocrine tumors cannot be excluded and subsequent management may be difficult to plan. We describe a very uncommon case of functioning glucagonoma associated with primary hyperparathyroidism (pHPT) in which genetic testing failed to detect germline mutations of MEN-1 and other known genes responsible for MEN1. CASE PRESENTATION: The patient, a 65-year old woman, had been suffering for more than 1 year from weakness, progressive weight loss, angular cheilitis, glossitis and, more recently, skin rashes on the perineum, perioral skin and groin folds. After multidisciplinary investigations, functioning glucagonoma and asymptomatic pHPT were diagnosed and, since family history was negative, sporadic MEN1 was suspected. However, genetic testing revealed neither MEN-1 nor other gene mutations responsible for rarer cases of MEN1 (CDKN1B/p27 and other cyclin-dependent kinase inhibitor genes CDKN1A/p15, CDKN2C/p18, CDKN2B/p21). The patient underwent distal splenopancreatectomy and at the 4-month follow-up she showed complete remission of symptoms. Six months later, a thyroid nodule, suspected to be a malignant neoplasia, and two hyperfunctioning parathyroid glands were detected respectively by ultrasound with fine needle aspiration cytology and 99mTc-sestamibi scan with SPECT acquisition. Total thyroidectomy was performed, whereas selective parathyroidectomy was preferred to a more extensive procedure because the diagnosis of MEN1 was not supported by genetic analysis and intraoperative intact parathyroid hormone had revealed "adenoma-like" kinetics after the second parathyroid resection. Thirty-nine and 25 months after respectively the first and the second operation, the patient is well and shows no signs or symptoms of recurrence. CONCLUSIONS: Despite well-defined diagnostic criteria and guidelines, diagnosis of MEN1 can still be challenging. When diagnosis is doubtful, appropriate management may be difficult to establish.

The Long Non-Coding BC200 Is a Novel Circulating Biomarker of Parathyroid Carcinoma.

Long non-coding RNAs (lncRNAs) are an important class of epigenetic regulators involved in both physiological processes and cancer development. Preliminary evidence suggested that lncRNAs could act as accurate prognostic and diagnostic biomarkers. Parathyroid cancer is a rare endocrine neoplasia, whose management represents a clinical challenge due to the lack of accurate molecular biomarkers. Our previous findings showed that human parathyroid tumors are characterized by a different lncRNAs signature, suggesting heterogeneity through the different histotypes. Particularly, we found that the lncRNA BC200/BCYRN1 could represent a candidate biomarker for parathyroid carcinomas (PCas). Here we aimed to extend our preliminary data evaluating whether BC200 could be an accurate non-invasive biomarker of PCas to support the clinical management of patients affected by parathyroid tumors at diagnosis, prognosis and follow-up. To provide a non-invasive point-of-care for parathyroid carcinoma diagnosis and follow-up, we analyzed BC200 expression in patients' serum through digital PCR. Our results show that BC200 counts are higher in serum from patients harboring PCa (n=4) compared to patients with parathyroid adenoma (PAd; n=27). Further, in PAd patients circulating BC200 levels are positively correlated with serum total calcium. Then, we found that BC200 is overexpressed in metastatic PCas (n=4) compared to non-metastatic ones (n=9). Finally, the lncRNA expression in PCa patients' serum drops are reduced after parathyroidectomy, suggesting its possible use in the post-operative setting for patients follow-up. Overall, these findings extend the knowledge on BC200 in parathyroid tumors, supporting its role as a useful biomarker for management of PCa.

Case report: Early-onset osteoporosis in a patient carrying a novel heterozygous variant of the WNT1 gene.

The WNT1 gene is crucial for bone development and homeostasis. Homozygous mutations in WNT1 cause severe bone fragility known as osteogenesis imperfecta type XV. Moreover, heterozygous WNT1 mutations have been found in adults with early-onset osteoporosis. We identified a 35 year-old Caucasian woman who experienced multiple vertebral fractures two months after her second pregnancy. There was no history of risk factors for secondary osteoporosis or family history of osteoporosis. Dual-energy X-ray absorptiometry confirmed a marked reduction of bone mineral density (BMD) at the lumbar spine (0.734 g/cm2, Z-score -2.8), femoral neck (0.48 g/cm2, Z-score -3.5), and total hip (0.589 g/cm2, Z-score -3.0). Blood tests excluded secondary causes of bone fragility. Genetic analysis revealed a heterozygous missense mutation (p.Leu370Val) in the WNT1 gene. Varsome classified it as a variant of uncertain significance. However, the fact that the Leucine residue at position 370 is highly conserved among vertebrate species and the variant has a very low allelic frequency in the general population would exclude the possibility of a polymorphism. The patient was treated for two years with teriparatide therapy associated with calcium and vitamin D supplements. During the follow-up period she did not report further clinical fractures. After 24 months of teriparatide, BMD increased at lumbar spine (+14.6%), femoral neck (+8.3%) and total hip (+4.9%) compared to baseline. We confirm that the heterozygous WNT1 mutation could cause a variable bone fragility and low turnover osteoporosis. We suggest that teriparatide is one of the most appropriate available therapies for this case.

Evaluation of formalin-fixed paraffin-embedded tissues in the proteomic analysis of parathyroid glands.

BACKGROUND: Proteomic research in the field of parathyroid tissues is limited by the very small dimension of the glands and by the low incidence of cancer lesions (1%). Formalin-fixed paraffin-embedded (FFPE) tissue specimens are a potentially valuable resource for discovering protein cancer biomarkers. In this study we have verified the applicability of a heat induced protein extraction from FFPE parathyroid adenoma tissues followed by a gel-based or gel-free proteomic approach in order to achieve protein separation and identification. RESULTS: The best results for high quality MS spectra and parameters, were obtained by using a gel-free approach, and up to 163 unique proteins were identified. Similar results were obtained by applying both SDS-out and SDS-out + TCA/Acetone techniques during the gel-free method. Western blot analysis carried out with specific antibodies suggested that the antigenicity was not always preserved, while specific immunoreactions were detected for calmodulin, B box and SPRY domain-containing protein (BSPRY), peroxiredoxin 6 (PRDX 6) and parvalbumin. CONCLUSIONS: In spite of some limitations mainly due to the extensive formalin-induced covalent cross-linking, our results essentially suggest the applicability of a proteomic approach to FFPE parathyroid specimens. From our point of view, FFPE extracts might be an alternative source, especially in the validation phase of protein biomarkers when a large cohort of samples is required and the low availability of frozen tissues might be constraining.

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.

Pseudohypoparathyroidism: Focus on Cerebral and Renal Calcifications.

CONTEXT: Pseudohypoparathyroidism (PHP) is a group of disorders characterized by hypocalcemia, hyperphosphatemia, and elevated parathyroid hormone (PTH) levels as a result of end-organ resistance to PTH. OBJECTIVE: To describe a cohort of 26 patients with PHP followed in a single tertiary center. METHODS: Clinical, biochemical, radiological, and genetic analysis of the GNAS gene in 26 patients recruited since 2002. RESULTS: Ten patients harbored a GNAS mutation, 15 epigenetic abnormalities at the GNAS locus, and 1 did not show genetic or epigenetic abnormalities. According to clinical, biochemical, and genetic features, patients were classified as PHP1A, PHP1B, and pseudopseudohypoparathyroidism. Patients with PHP1A had an earlier diagnosis and more cases with family history, Albright hereditary osteodystrophy (AHO) features, hormonal resistance, and hypertension. Obesity was a common feature. No difference in biochemical values was present among PHP1A and PHP1B. Intracerebral calcification occurred in 72% of patients with no difference among PHP1A and PHP1B subgroups. No significant difference was observed between patients with and without intracerebral calcification for the time-weighted average values of total serum calcium, phosphate, calcium-phosphate product, and PTH fold increase. A borderline association between cerebral calcification and age at the time of diagnosis (P = .04) was found in the whole cohort of patients. No renal calcifications were found in the overall cohort. CONCLUSION: Patients with PHP1A more frequently have AHO features as well as hypertension than patients with PHP1B. Patients with PHP presented a high rate of intracerebral calcification with no significant difference between subgroups. No increased risk of renal calcifications was also found in the entire cohort.

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 ±â€…17 years vs 55 ±â€…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 ±â€…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 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.

Gene expression profile in metastatic and non-metastatic parathyroid carcinoma.

Parathyroid carcinoma (PC) is one of the rarest and aggressive malignancies of the endocrine system. In some instances, the histological diagnosis remains uncertain unless there is evidence of gross local invasion or secondary spread. The identification of molecular markers could improve the diagnostic accuracy of these lesions. The expression of 740 genes involved in the tumor progression processes was assessed in 8 parathyroid adenomas (PAs), 17 non-metastatic and 10 metastatic PCs using NanoString technology. Clustering analysis and Ingenuity Pathway Analysis (IPA) were interrogated to compare the gene expression profiles among the three analyzed groups and to evaluate the potential role of differentially expressed genes, respectively. The 103 differentially expressed genes between metastatic PCs and PAs are able to discriminate perfectly the two groups from a molecular point of view. The molecular signatures identified in non-metastatic PCs vs PAs and in metastatic PCs vs non-metastatic PCs comparisons, although with some exceptions, seem to be histotype-specific IPA reveals that hepatic fibrosis/hepatic stellate cell activation and GP6 signaling pathway are involved in malignant behavior of parathyroid tumors, whereas the activation of the HOTAIR regulatory pathway are involved in the metastatization process. Our investigation identified differentially expressed genes in non-metastatic PCs mainly encoding ECM proteins and in metastatic PCs driving endothelial-to-mesenchymal transition or encoding mediators of angiogenesis. The identified genes might be promising molecular markers potentially useful in the clinical practice for the early diagnosis and prognosis of PC.

Late-onset postsurgical hypoparathyroidism following parathyroidectomy for recurrent primary hyperparathyroidism: a case report and literature review.

PURPOSE: Previously in 1987, a 21-year-old male was diagnosed with primary hyperparathyroidism (PHPT) when a right inferior parathyroid adenoma was removed. PHPT recurred after 3 and 6 years and on both occasions was cured by resection of parathyroid adenomas. At 52 years of age, the patient developed a late-onset hypoparathyroidism (HP), even though postsurgical HP typically occurs as a transient or permanent form soon after neck surgery. The purpose of this work was to report the follow-up of the patient and to review prior cases of late-onset postsurgical HP. METHODS: Prior cases of late-onset postsurgical HP were searched and reviewed focusing on clinical and biochemical features. RESULTS: The patient's asymptomatic hypocalcemia with total serum calcium at 8.2 mg/dL was initially documented in September 2018; PTH was inappropriately low at 15 ng/mL. In February 2020, a mild hypocalcemia was confirmed with low-normal PTH at 15 ng/mL. Autoimmune and familial causes of HP were ruled out including the presence of stimulating autoantibodies against calcium-sensing receptor. Instead, a progressive damage or atrophy of the parathyroid gland(s) ensuing years after surgery is believed to have led to the patient's hypocalcemia. All 19 previously reported cases of late-onset postsurgical HP occurred after thyroid surgery, with no examples of the condition being found following parathyroidectomy. CONCLUSIONS: The case highlights the rare occurrence of late-onset postsurgical HP in a patient who had had multiple parathyroidectomies for PHPT. Thus, monitoring serum calcium, phosphate, and PTH during follow-up of such patients is recommended.

Hypomagnesuria is Associated With Nephrolithiasis in Patients With Asymptomatic Primary Hyperparathyroidism.

CONTEXT: The pathogenesis of nephrolithiasis in primary hyperparathyroidism (PHPT) remains to be elucidated. The latest guidelines suggest parathyroidectomy in patients with asymptomatic PHPT with hypercalciuria (> 400 mg/d) and increased stone risk profile. OBJECTIVE: The objective of this work is to evaluate the association of urinary stone risk factors and nephrolithiasis in patients with asymptomatic sporadic PHPT and its clinical relevance. DESIGN: A total of 157 consecutive patients with sporadic asymptomatic PHPT were evaluated by measurement of serum and 24-hour urinary parameters and kidney ultrasound. RESULTS: Urinary parameters were tested in the univariate analysis as continuous and categorical variables. Only hypercalciuria and hypomagnesuria were significantly associated with nephrolithiasis in the univariate and multivariate analysis adjusted for age, sex, body mass index, estimated glomerular filtration rate, parathyroid hormone, 25-hydroxyvitamin D, serum calcium, and urine volume (odds ratio, OR 2.14 [1.10-4.56]; P = .04; OR 3.06 [1.26-7.43]; P = .013, respectively). Hypomagnesuria remained associated with nephrolithiasis in the multivariate analysis (OR 6.09 [1.57-23.5], P = .009) even when the analysis was limited to patients without concomitant hypercalciuria. The urinary calcium/magnesium (Ca/Mg) ratio was also associated with nephrolithiasis (univariate OR 1.62 [1.27-2.08]; P = .001 and multivariate analysis OR 1.74 [1.25-2.42], P = .001). Hypomagnesuria and urinary Ca/Mg ratio had a better, but rather low, positive predictive value compared with hypercalciuria. CONCLUSIONS: Hypomagnesuria and urinary Ca/Mg ratio are each associated with silent nephrolithiasis and have potential clinical utility as risk factors, besides hypercalciuria, for kidney stones in asymptomatic PHPT patients. The other urinary indices that have been commonly thought to be associated with kidney stones in PHPT are not supported by our results.

Parathyroid Carcinoma.

Parathyroid carcinoma (PC) is a rare endocrine malignancy, accounting for <1% of all cases of sporadic primary hyperparathyroidism (PHPT) and up to 15% in the hereditary hyperparathyroidism-jaw tumor syndrome. Genomic alterations identified in PC are mostly represented by CDC73 gene mutations, codifying for a loss-of-function protein termed parafibromin. Whole exome sequencing identified mutations in other genes, such as mTOR, KMT2D, CDKN2C, THRAP3, PIK3CA, and EZH2 genes, CCND1 gene amplification. The diagnosis of PC is quite difficult due to the lack of reliable clinical diagnostic criteria, and in the majority of cases is made postoperatively at histological examination. The clinical manifestations of PC are primarily due to the excessive secretion of PTH by the tumor rather than spread to local or distant organs. En bloc resection of the parathyroid tumor represents the initial mainstay treatment of patients with PC. Multiple surgical procedures may be required, although surgical morbidity should be taken into account. A 5- and 10-year survival between 77-100 and 49-91%, respectively, has been reported. When the tumor is no more resectable, medical treatment of hypercalcemia has a pivotal role in the management of these patients.

Atypical parathyroid adenomas: challenging lesions in the differential diagnosis of endocrine tumors.

Atypical parathyroid adenomas represent a group of intermediate form of parathyroid neoplasms of uncertain malignant potential which show some atypical histological features that represent a challenge for the differential diagnosis with parathyroid carcinomas. They may occur as sporadic or as a part of hereditary syndromes. The molecular signature of these neoplasms is still unknown and the germline CDC73 mutations appears to be the most common anomaly in this setting suggesting that these cases might represent variants of the hyperparathyroidism-jaw tumor syndrome. The identification of markers predicting the outcome is of great importance to guide an adequate postoperative monitoring and, the same time, relieve of the anxiety of relatively strict monitoring patients not at risk. This review will summarize the current knowledge of the clinical, biochemical, molecular and histological profile of atypical parathyroid adenomas.

Parathyroid carcinoma: a clinical and genetic perspective.

Parathyroid carcinoma (PC) is a rare neoplasia difficult to diagnose preoperatively. It mainly occurs as a sporadic disease but also as part of familial PHPT. At variance with patients with the benign counterpart, the phenotype of these patients is characterized by a severe primary hyperparathyroidism (PHPT). The clinical features are mostly due to the effects of the excessive secretion of PTH by the functioning tumor and hypercalcemia rather than to the tumor burden. The prognosis is poor and unmanageable hypercalcemia accounts for death in the majority of cases. The best chance of cure is surgery, although persistent or recurrent disease occurs in about 50% of patients. Somatic loss-of-function mutations of CDC73 gene, encoding parafibromin, are the most frequent genetic alterations occurring in PCs. Mutations of the PRUNE2 gene, alterations of the PI3K/AKT/mTOR pathway and amplification of the CCND1 gene have been recently detected in PCs. Alteration of microRNA profile and methylation pattern have been identified in PCs. The recent studies have better defined the genomic landscape of PCs and represent major progress toward a full molecular characterization of this neoplasia and development of novel therapeutic options.