Parafibromin Expression Research Articles

CDC73 c.1155-3A > G is a pathogenic variant that causes aberrant splicing, disrupted parafibromin expression and hyperparathyroidism-jaw tumor syndrome

Abstract Germline and somatic pathogenic variants in the CDC73 gene, encoding the nuclear protein parafibromin, increase the risk for parathyroid carcinoma and cause hereditary primary hyperparathyroidism (PHPT) syndromes known as familial isolated hyperparathyroidism (FIHP) and hyperparathyroidism-jaw tumor syndrome (HPT-JT). The identification of pathogenic germline variants in PHPT-susceptibility genes can influence surgical planning for parathyroidectomy, guide screening for potential syndromic manifestations, and identify/exonerate at-risk family members. Numerous types of pathogenic germline variants have been described for CDC73-related conditions including deletion, truncating, missense, and splice site mutations. Here, we report identification of a non-coding germline CDC73 variant (CDC73 c.1155-3A > G), previously categorized as a variant of uncertain significance (VUS), in a family with HPT-JT. This variant, found in two family members with PHPT, altered CDC73 splicing in peripheral blood cells and disrupted parafibromin immunostaining in associated parathyroid adenomas: strongly evidencing its pathogenicity. Sestamibi scintigraphy yielded nondiagnostic localization results for both patients’ parathyroid adenomas, consistent with prior studies suggesting lower sensitivity for small or cystic lesions. Our findings demonstrate key aspects of CDC73-related disorders, highlight the diagnostic value of RNA testing and exemplify the importance of obtaining a thorough, three-generational family history.

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.

The role of immunohistochemical examination in the differential diagnosis of atypical tumors and carcinomas of parathyroid glands

Studying the role of IHC analysis in the differential diagnosis of APT and PC. The study included 44 patients with morphologic diagnosis of the APT established after surgical treatment for primary hyperparathyroidism on the basis of Endocrinology Research Centre during 2018-2023. All cases underwent IHC examination with evaluation of CD31/CD34 and parathormone (PTH) expression for identification of vascular invasion, Ki-67, parafibromin. According to the results of IHC analysis in 8/44 patients (18.2%) the diagnosis of APT was revised in favor of the PC: in 7 of them vascular invasion was detected; in 1 patient the additional series of slices in the surrounding fatty tissue revealed foci of tumor growth, confirmed by positive reaction with antibodies to PTH. According to IHC results, the material was divided into 2 groups: APT and PC. There were no differences in clinical and morphological characteristics, Ki-67% level and parafibromin expression between the groups. Assessment of clinical and laboratory-instrumental data at the preoperative stage does not allow differentiating APT from PC. In case of APT diagnosis and detection of suspicious morphological features, it is necessary to perform IHC examination to exclude PC.

FRI692 Severe Hyperparathyroidism And Nephrolithiasis In An Adolescent Male Due To CDC73 Positive Parathyroid Carcinoma

Abstract Disclosure: J.T. Nguyen: None. D.H. Geller: None. A. Ryabets-Lienhard: None. Introduction: Parathyroid carcinoma is a rare cause of primary hyperparathyroidism in the pediatric population, with only 20 previously reported cases. Variations in the CDC73 gene have been associated with sporadic parathyroid carcinoma, autosomal dominant hyperparathyroidism-jaw tumor syndrome (HPT-JT), and familial isolated hyperparathyroidism (FIHP). To our knowledge, only 3 cases of pediatric parathyroid carcinoma with confirmed variants of CDC73 have been reported. We present a case of severe hyperparathyroidism and nephrolithiasis due to parathyroid carcinoma caused by a pathogenic variant in CDC73 in a pediatric patient, highlighting the importance of early recognition and management. Clinical Case: An otherwise asymptomatic 14-year-old male presented with one year of recurrent nephrolithiasis. Initial tests demonstrated hypercalcemia (13.8 mg/dL, 8.4-10.2 mg/dL), normal phosphorous, elevated PTH (1,379 pg/mL, 7.5-53.5 pg/mL), and elevated alkaline phosphatase (514 U/L, 30-250 U/L). The hypercalcemia was treated with hyperhydration, furosemide, and pamidronate. Sestamibi scan revealed a focus of abnormal uptake suggestive of a left parathyroid mass, with ultrasonographic demonstration of a predominantly solid, hypoechoic, and vascular mass centered posterior to the inferior left thyroid lobe. Skeletal survey was notable for trabecular abnormalities and osteopenia. He underwent a left parathyroid mass excision. Final pathology confirmed the parathyroid carcinoma, with multiple foci of vascular invasion without evidence of capsular involvement. Immunohistochemistry demonstrated diffuse positivity for PTH and loss of parafibromin expression by the tumor cells. Genetic testing revealed a pathogenic germline heterozygous nonsense variant in CDC73 (c.376C>T(p.Arg126Ter)) resulting in protein truncation. Post-operative PTH was undetectable with normal calcium and phosphorous. Calcitriol, cholecalciferol, and calcium carbonate supplementation were implemented to prevent further hypocalcemia due to transient hypoparathyroidism and hungry bone syndrome. Calcium supplementation was discontinued within one year of his surgery. Serial thyroid ultrasounds and CT scans have been negative for recurrent or residual disease without evidence of metastasis. Mandibular x-ray showed no evidence of tumors or lesions involving the jaw. He has been noted to have small right renal cysts without other kidney abnormalities. Conclusion: Severe hyperparathyroidism due to parathyroid carcinoma can present as recurrent nephrolithiasis in an otherwise asymptomatic individual. Pediatric patients with a longstanding history of kidney stones should undergo screening for hypercalcemia and hyperparathyroidism even in the absence of other signs and symptoms of elevated calcium to ensure timely diagnosis and appropriate management. Presentation: Friday, June 16, 2023

The clinicopathological and prognostic significances of CDC73 expression in breast cancer: A pathological and bioinformatics analysis.

Parafibromin is a protein encoded by the oncosuppressor CDC73 gene, whose mutation results in hyperparathyroidism-jaw tumor syndrome (HPT-JT) and parathyroid carcinoma. Down-regulation of parafibromin is linked to lung, gastric, colorectal, and ovarian cancer tumorigenesis. Parafibromin expression was detected by RT-PCR, bioinformatics analysis, Western blot, and immunohistochemistry; and compared with clinicopathological characteristics of breast cancer. CDC73-related genes and pathways were analyzed using bioinformatics analysis. Parafibromin expression was increased in breast cancer compared to normal tissues at both mRNA and protein levels (p<0.05). Among triple-negative breast cancers, it was higher in basal-like 1 than basal-like 2 patients (p<0.05) and mesenchymal than immunomodulatory patients (p<0.05). CDC73 mRNA expression was positively correlated with white race, non-infiltrating immune cells, favorable luminal subtypes of PAM50, and prognosis of breast cancer patients (p<0.05). The differential genes of CDC73 were classified into enzyme inhibitors, peptidase, and keratinization by KEGG (p<0.05). Similarly, it was classified into ribosomes, TGF-β, oxidation phosphorylation, inositol phosphate metabolism, arachidonic acid metabolism, linoleic acid metabolism, ERBB, and VEGF signaling pathways by GSEA (p<0.05). The positively-correlated genes of CDC73 were involved in cell mobility, response to interferon α, nuclear pore and basket, and histone methyltransferase. The negatively-correlated genes of CDC73 were involved in the mitochondrial respiratory chain, thermogenesis, and ribosomes. Parafibromin expression was higher in invasive ductal than lobular carcinoma (p<0.05) and mucinous adenocarcinoma than others (p<0.05). Parafibromin immunoreactivity as an independent factor was positively associated with an increased overall survival rate of breast cancer patients (p<0.05). These findings suggest that up-regulation of parafibromin in breast cancer patients is closely linked to a favorable prognosis. It is involved in tumorigenesis and subsequent progression by regulating metabolism, ribosomes, and cytokines.

Genomic Profiling Reveals the Variant Landscape of Sporadic Parathyroid Adenomas in Chinese Population.

To define somatic variants of parathyroid adenoma (PA) and to provide novel insights into the underlying molecular mechanism of sporadic PA. Basic clinical characteristics and biochemical indices of 73 patients with PA were collected. Whole-exome sequencing was performed on matched tumor-constitutional DNA pairs to detect somatic alterations. Functional annotation was carried out by ingenuity pathway analysis afterward. The protein expression of the variant gene was confirmed by immunohistochemistry, and the relationship between genotype and phenotype was analyzed. Somatic variants were identified in 1549 genes, with an average of 69 variants per tumor (range, 13-2109; total, 9083). Several novel recurrent somatic variants were detected, such as KMT2D (15/73), MUC4 (14/73), POTEH (13/73), CD22 (12/73), HSPA2 (12/73), HCFC1 (11/73), MAGEA1 (11/73), and SLC4A3 (11/73), besides the previously reported PA-related genes, including MEN1 (11/73), CASR (6/73), MTOR (4/73), ASXL3 (3/73), FAT1 (3/73), ZFX (5/73), EZH1 (2/73), POT1 (2/73), and EZH2 (1/73). Among them, KMT2D might be the candidate driver gene of PA. Crucially, 5 patients carried somatic mutations in CDC73, showed an aggressive phenotype similar to that of parathyroid carcinoma (PC), and had a decreased expression of parafibromin. Pathway analysis of recurrent potential PA-associated driver variant genes revealed functional enrichments in the signaling pathway of Notch. Our study expanded the pathogenic variant spectrum of PA and indicated that KMT2D might be a novel candidate driver gene and be considered as a diagnostic biomarker for PA. Meanwhile, CDC73 mutations might be an early developmental event from PA to PC. The results provided insights into elucidating the pathogenesis of parathyroid tumorigenesis and a certain basis for clinical diagnosis and treatment.

Genetic and Epigenetic Alterations in Parathyroid Neoplasms.

The exact etiology of parathyroid carcinomas (PC) is still unknown. Their associations have with several inherited syndromes or specific genetic lesions have been established. The management of PC is challenging for clinicians. The complexity of molecular phenotypes increases with tumor aggressiveness. Lack of parafibromin on immunohistochemistry staining and HRPT2 mutation would be helpful in differentiation of carcinoma from adenoma. Lack of parafibromin expression, the gene product of HRPT2 is now used as a diagnostic, prognostic, and predictive marker for parathyroid carcinoma. The epigenetic alteration, for example, DNA methylation and modifications in the chromatin structure, are known as significant events involved in the parathyroid tumorigenesis. We suggest that adjuvant genetic and epigenetic target therapy should be considered in treatment of the patients with PC.

Association Between Parafibromin Expression and Presence of Brown Tumors and Jaw Tumors in Patients with Primary Hyperparathyroidism: Series of Cases with Review of the Literature

BACKGROUND Brown and jaw tumors are rare entities of poorly understood etiology that are regarded as end-stage of bone remodeling in patients with long-lasting and chronic hyperparathyroidism. Jaw tumors are mainly diagnosed in jaw tumors syndrome (HPT-JT syndrome) and are caused by mutation in the CDC73 gene, encoding parafibromin, a tumor suppressing protein. The aim of this work is to present 4 cases of patients in whom the genetic mutation of the CDC73 gene and clinical presentation coexist in an unusual setting that has not yet been described. CASE REPORT We present cases of 4 patients with primary hyperparathyroidism. Three were diagnosed with brown tumors (located in long bones, ribs, iliac, shoulders) and 1 with brown and jaw tumors. Expression of parafibromin in affected parathyroid tissues were analyzed. In patients without positive parafibromin staining, we searched for CDC73 mutation using next-generation sequencing. Parafibromin staining was positive in 1 patient with brown tumors and was negative in 2 individuals with brown tumors and 1 with brown and jaw tumors. CDC73 mutation was detected in two-thirds of patients (60%) with negative staining for parafibromin and brown tumors. MEN1 mutation was found in the patient with brown tumor and positive staining for parafibromin. CONCLUSIONS Patients with hyperparathyroidism and coexistence of brown tumors or jaw tumors might have decreased expression of parafibromin in parathyroid adenoma tissue, which might be caused by CDC73 mutation and suggest a genetic predisposition. Further research on much larger study groups is needed.

Diagnostic significance of parafibromin expression in parathyroid carcinoma

Parathyroid carcinomas are difficult to distinguish from adenomas according to the current diagnostic criteria. The judgment of local infiltration is subjective and inconsistent. Existing studies have found that the CDC73 gene encoding parafibromin is related to the occurrence of parathyroid carcinomas. This study is aimed at investigating whether the immunohistochemistry of parafibromin is helpful in distinguishing malignant from benign parathyroid tumors. A total of 53 patients with parathyroid carcinoma from Peking Union Medical College Hospital were included. Metastasis was found in 17 of 53 patients. In addition, another 53 patients with parathyroid adenomas were included as controls. Appropriate sections were stained with an immunohistochemical autostainer. Three senior pathologists evaluated the sections and analyzed their clinicopathological features independently. The loss of parafibromin expression only occurred in malignant tumors, including all carcinomas with metastasis (17/17) and 14 of 36 carcinomas with only local infiltration. All staining results of adenomas (53/53) were positive. Considering invasion as the gold standard of malignancy, the sensitivity of parafibromin staining is 58%, and the specificity is 100%. If the gold standard is changed to metastasis, the sensitivity becomes 100%, and the specificity becomes 84%. By analyzing clinicopathological features with metastasis and parafibromin staining, it is found that local-infiltrative carcinomas with positive staining results have better biological behaviors than carcinomas that lack parafibromin expression. Parafibromin staining is highly recommended as an auxiliary method in the diagnosis of parathyroid carcinoma.

Parafibromin Is Highly Expressed in Hepatocellular Carcinoma and Its Expression Correlates with Poor Prognosis

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death worldwide. Much progress has been made regarding the understanding of hepatocarcinogenesis, yet the long-term survival rate of HCC patients remains poor. Recent efforts have shown parafibromin has a pathologic role in many human cancers, but little is known about the effects of parafibromin in HCC. This study aimed to investigate the pattern of parafibromin expression and its clinicopathologic significance in human HCC. Immunohistochemical analysis of HCC and matched non-tumor liver tissues from 50 HCC patients showed that the nuclear expression of parafibromin was higher in HCC tissues (50/50 cases) than in non-tumor liver tissues (17/50 cases). Moreover, elevated parafibromin expression was found to be significantly correlated with the presence of microvascular invasion (p = 0.017), hepatitis virus infection-induced occurrence (p = 0.005), and poorer tumor differentiation (Edmondson–Steiner grade; p = 0.000). Kaplan–Meier analysis showed that HCC patients with elevated parafibromin expression had poorer recurrence-free (p = 0.014, log-rank test = 6.079) and overall survival (p = 0.036, log-rank test = 4.414). These findings indicate parafibromin may be related to the pathogenesis of HCC and a potential prognostic marker for HCC patients after hepatectomy.

Role of MDM2, CDK4, BCL2, Parafibromin and Galectin 1 in Differentiating Osteosarcoma from its Benign Fibro-osseous Lesions.

Benign fibro-osseous lesions (BFOLs) are a diverse group of lesions showing considerable degree of overlap with low grade osteosarcoma (LGOS). Further, de-differentiated osteosarcoma (DOS) is usually indistinguishable from conventional high-grade OS (COS) if LGOS foci are not identified. Thus, there is a need for adjunctive immunohistochemical markers to differentiate OS from benign FOLs as well as DOS from COS. This study evaluated the role of immunohistochemical expression of MDM2, CDK4, parafibromin, BCL-2 and Galectin-1 (Gal-1) in accurate characterization of benign FOLs and in differentiating them from OS. From our archives, we retrieved 101 tissue samples which were diagnosed as osteosarcoma (OS) /ossifying fibroma (OF) / fibrous dysplasia (FD) or fibrous hyperplasia (FH) and examined their immunohistochemical staining pattern with the aforementioned antibodies. MDM2 showed 100% specificity for diagnosing OS. CDK4 and Gal-1 showed linear increase in immunoexpression from benign BFOLs to OS. BCL-2 showed equivocal immunopositivity in OF and OS, but the positivity was higher than that observed in FD. The highest immunoexpression for parafibromin was seen in FD followed by OF and OS cases. Thus, MDM2 is most specific, and Gal-1 is most sensitive of all the markers studied in differentiating OS from benign mimics. Combination of these two markers can be used as an adjunct to conventional imaging and microscopy in accurate characterization of these lesions. Further MDM2 overexpression can differentiate DOS and COS.

Diagnostic Significance of Parafibromin Expression in Parathyroid Carcinoma

Diagnostic Significance of Parafibromin Expression in Parathyroid Carcinoma

Filamin A and parafibromin expression in parathyroid carcinoma.

Parathyroid carcinoma (PC), atypical parathyroid tumours (APT) and parathyroid adenoma (PA), all present with hypercalcemia. Diminished calcium-sensing receptor (CaSR) expression is reported in PC but is rare in benign tumours. Filamin A (FLNA) binds to the CaSR and activates the mitogen-activated protein kinase (MAPK) signalling pathway. FLNA is related to tumour aggressiveness in several cancers, but its role in parathyroid neoplasia is unknown. We examined FLNA, CaSR and parafibromin expression in PCs (n = 32), APTs (n = 44) and PAs (n = 77) and investigated their potential as diagnostic and/or prognostic markers. Tissue microarray slides were immunohistochemically stained with antibodies for FLNA, CaSR and parafibromin. Staining results were correlated with detailed clinical data. All tumours stained positively for CaSR, with two tumours (one PC and one APT) showing diminished expression. Carcinomas were characterized by increased cytoplasmic FLNA expression compared to APTs and PAs (P = 0.004). FLNA expression was not correlated with Ki-67 proliferation index or loss of parafibromin expression. Cytoplasmic FLNA expression was also associated with higher serum calcium, PTH concentrations and male sex (P = 0.014, P = 0.017 and P = 0.049 respectively). Using a combined marker score, we found that parathyroid tumours with low FLNA expression and positive parafibromin staining were extremely likely to be benign (P < 0.001). Cytoplasmic and membranous FLNA expression is increased in parathyroid carcinomas compared to benign tumours. A combined FLNA and parafibromin expression score shows potential as a prognostic predictor of indolent behaviour in parathyroid neoplasms.

A novel long-range deletion spanning CDC73 and upper-stream genes discovered in a kindred of familial primary hyperparathyroidism.

To confirm the exact break-point of a novel long-range deletion discovered in one female parathyroid carcinoma (PC) patient who has a strong family history suggesting familial hyperparathyroidism, and to investigate the expression of parafibromin in the patient's affected lesion. Clinical information of one female patient as well as five of her relatives was collected. Their genomic DNA extracted from peripheral blood went through Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA). After completing whole genome sequencing (WGS), clone sequencing was also performed, whose result was aligned with standard human genome database after Sanger sequencing. The medical history of recurrent hypercalcemia after parathyroidectomy and histopathological investigation confirmed that the female patient was diagnosed with PC. WGS displayed a novel 130 kb long-range deletion spanning UCHL5 to CDC73 that was later confirmed by clone sequencing. MLPA showed similar results in four of her five relatives, suggesting these people to be carriers of the same long-range deletion, and three among them had a history of primary hyperparathyroidism (PHPT) ahead of the proband's first visit. We discovered a novel 130 kb long-range deletion spanning CDC73 in a family of 5 persons, and the existence of the deletion was related to PHPT and PC. Our discovery validated the role of CDC73 mutation in the occurrence of PHPT and PC, which provided new information to the genetic studies of PC.

Renal Neoplasia in Hyperparathyroidism–Jaw Tumor Syndrome

A male patient in his late teens presented with primary hyperparathyroidism and underwent a parathyroidectomy. Germline testing revealed a pathogenic truncating alteration of the CDC73 gene (c.25C>T; p.Arg9Ter). On the basis of these findings, he was diagnosed with hyperparathyroidism–jaw tumor syndrome. In addition, multiple first-degree family members including his father and brother were found to have this syndrome. Approximately 2 decades later, he was found to have a 1.1-cm left renal mass on routine surveillance imaging. This was treated with a partial nephrectomy, and representative images of the renal tumor (hematoxylin and eosin stain, magnification ×100) are shown in Figure 1. This tumor showed a combination of papillary and nested architecture and exhibited inconspicuous nucleoli (World Health Organization grade 1). No recurrences or metastases were identified at 154 months of follow-up. What immunohistochemistry-based marker can be used to screen for tumors arising secondary to hyperparathyroidism–jaw tumor syndrome and what is the expected pattern of expression?a.Calcitonin, loss of stainingb.Parathormone, loss of stainingc.Parafibromin, loss of stainingd.Parafibromin, diffuse overexpression Answer: c Hyperparathyroidism–jaw tumor syndrome is inherited in an autosomal dominant manner secondary to pathogenic mutations of the CDC73 gene.1Carpten J.D. Robbins C.M. Villablanca A. et al.HRPT2, encoding parafibromin, is mutated in hyperparathyroidism–jaw tumor syndrome.Nat Genet. 2002; 32: 676-680Crossref PubMed Scopus (553) Google Scholar Specifically, the pathogenic CDC73 c.25C>T, p.Arg9Ter alteration has been reported in both the somatic and germline setting.1Carpten J.D. Robbins C.M. Villablanca A. et al.HRPT2, encoding parafibromin, is mutated in hyperparathyroidism–jaw tumor syndrome.Nat Genet. 2002; 32: 676-680Crossref PubMed Scopus (553) Google Scholar,2Cetani F. Pardi E. Borsari S. et al.Genetic analyses of the HRPT2 gene in primary hyperparathyroidism: germline and somatic mutations in familial and sporadic parathyroid tumors.J Clin Endocrinol Metab. 2004; 89: 5583-5591Crossref PubMed Scopus (189) Google Scholar These patients typically present with primary hyperparathyroidism secondary to parathyroid tumors, and in a subset of these patients, ossifying fibromas of the maxilla and mandible develop.1Carpten J.D. Robbins C.M. Villablanca A. et al.HRPT2, encoding parafibromin, is mutated in hyperparathyroidism–jaw tumor syndrome.Nat Genet. 2002; 32: 676-680Crossref PubMed Scopus (553) Google Scholar Renal manifestations in this syndrome include cysts, hamartomas, metanephric adenoma, and Wilms tumor.1Carpten J.D. Robbins C.M. Villablanca A. et al.HRPT2, encoding parafibromin, is mutated in hyperparathyroidism–jaw tumor syndrome.Nat Genet. 2002; 32: 676-680Crossref PubMed Scopus (553) Google Scholar,3Carlo M.I. Hakimi A.A. Stewart G.D. et al.Familial kidney cancer: implications of new syndromes and molecular insights.Eur Urol. 2019; 76: 754-764Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar,4Gupta S. Vanderbilt C.M. Leibovich B.C. et al.Secondary renal neoplasia following chemotherapy or radiation in pediatric patients.Hum Pathol. 2020; 103: 1-13Crossref PubMed Scopus (5) Google Scholar The spectrum of renal neoplasia in hyperparathyroidism–jaw tumor syndrome is poorly defined because of the rarity of these tumors and limited reports of detailed histopathologic findings.3Carlo M.I. Hakimi A.A. Stewart G.D. et al.Familial kidney cancer: implications of new syndromes and molecular insights.Eur Urol. 2019; 76: 754-764Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar,4Gupta S. Vanderbilt C.M. Leibovich B.C. et al.Secondary renal neoplasia following chemotherapy or radiation in pediatric patients.Hum Pathol. 2020; 103: 1-13Crossref PubMed Scopus (5) Google Scholar As the CDC73 gene encodes the parafibromin protein, immunohistochemistry for parafibromin has been proposed as a screening tool for tumors occurring in the context of hyperparathyroidism–jaw tumor syndrome.5Andrici J. Gill A.J. Hornick J.L. Next generation immunohistochemistry: emerging substitutes to genetic testing?.Semin Diagn Pathol. 2018; 35: 161-169Crossref PubMed Scopus (17) Google Scholar Loss of nuclear expression of parafibromin is thought to correlate with pathogenic loss of function alterations of CDC73 and has been proposed as an immunohistochemistry-based screening tool.5Andrici J. Gill A.J. Hornick J.L. Next generation immunohistochemistry: emerging substitutes to genetic testing?.Semin Diagn Pathol. 2018; 35: 161-169Crossref PubMed Scopus (17) Google Scholar This renal tumor exhibited papillary and nested architecture and a cytokeratin 7–positive immunophenotype (Figure 2A-C). Immunohistochemistry for parafibromin showed loss of nuclear expression in tumor cells, in contrast to retained expression in non-neoplastic vascular elements (Figure 2D). In addition to the patient described herein, loss of parafibromin expression has been reported in metachronous renal tumors (metanephric adenomas) for at least 1 other patient with this syndrome.4Gupta S. Vanderbilt C.M. Leibovich B.C. et al.Secondary renal neoplasia following chemotherapy or radiation in pediatric patients.Hum Pathol. 2020; 103: 1-13Crossref PubMed Scopus (5) Google ScholarView Large Image Figure ViewerDownload Hi-res image Download (PPT)

Parafibromin Abnormalities in Ossifying Fibroma.

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

Atypical Parathyroid Adenoma in a Young Man

Patient is a 38-year-old man who developed sudden onset of pain in the upper left arm while carrying a case of water. The pain recurred periodically over the next few months. He presented to the emergency department where imaging showed a pathologic fracture in the proximal left humerus through a lytic lesion. Laboratory testing showed: calcium 13.8 mg/dL (8.5–10.1 mg/dL), 25-OH vitamin D 8 ng/mL (31–100 ng/mL), parathyroid hormone 1583.1 pg/mL (18.5–88 pg/mL). Neck ultrasound showed a complex nodule in the left neck measuring 4.2 x 1.7 x 2.5 cm. Subsequent biopsy of the left arm lesion showed a Brown tumor. The patient was referred to endocrinology. There was concern for parathyroid carcinoma given the elevated parathyroid hormone and large neck lesion. Technetium-99m sestamibi scan showed a 4.1 x 2.6 x 2.5 cm mass posterior to the left thyroid lobe. He subsequently underwent left hemithyroidectomy and parathyroidectomy. Pathology revealed a 3.1 cm parathyroid mass with scattered fibrous bands, foci of prominent nucleoli and foci of sheet-like trabecular and spindled architecture. It was without necrosis, lymphovascular invasion, perineural invasion, increased mitotic activity, atypical mitoses or invasion into adjacent structures. Thus, it was classified as an atypical parathyroid adenoma.Primary hyperparathyroidism is the third most common endocrine disorder, but fewer than 2% occur as a result of an atypical parathyroid adenoma. Patients with an atypical parathyroid adenoma tend to have a more dramatic clinical presentation compared to those with classic adenoma. We see higher calcium and parathyroid hormone levels. Atypical parathyroid adenomas are classified as such due to other features which place the lesion at a higher risk for malignant behavior including higher mitotic activity, adherence to adjacent structures, banding fibrosis and a growth pattern that is either solid or trabecular. In contrast to parathyroid carcinoma, atypical parathyroid adenomas do not show invasion into the surrounding tissues or lymphatic/vascular vessels, and there should be no evidence of metastatic disease. The exact definition of an atypical parathyroid adenoma varies among institutions, and recognition of the defining features (or lack thereof) necessitates an experienced endocrine pathologist.Due to their uncertain malignant potential, patients with an atypical parathyroid adenoma should undergo routine surveillance for recurrence. Routine follow-up of calcium, parathyroid hormone and imaging is indicated to detect for recurrence. A CDC73 germline mutation is associated with recurrence compared to CDC73-negative patients. Parafibromin expression is also thought to play a role although studies so far have had discrepant results.

Molecular profile of parathyroid tissues and tumours: a heterogeneous landscape.

Advances in laboratory diagnostics and surgical treatment ofprimary hyperparathyroidism have ensured solid basis for research in parathyroid pathology in order to specify key molecules in pathogenesis and morphological diagnostics ofdifficult cases. Theaim ofthis study was to assess themolecular landscape and its heterogeneity in primary parathyroid hyperplasia (PPH) and adenoma, compared to carcinoma and normal glands. In aretrospective analysis of179 surgically removed parathyroid glands (102 adenomas; 27 PPH; 45 normal glands; 5 carcinomas), expression ofKi-67, p21, p27, p53, cyclin D1, Bcl-2 protein, vimentin, cytokeratin (CK) 19, E-cadherin, CD56, CD44 and parafibromin was detected by immunohistochemistry, followed by computer-assisted assessment ofmean values and heterogeneity measures. Descriptive statistics and Kruskal-Wallis test were applied. Significant differences were disclosed regarding themean and highest fraction ofKi-67 (both p < 0.001), p21 (both p < 0.001), cyclin D1 (p = 0.002) and p27-expressing cells (p = 0.010). Proliferative lesions (PPH, adenoma and carcinoma) showed statistically significantly up-regulated CK19 (p = 0.012), decreased E-cadherin levels and distinctive patterns ofvimentin. CD44, CD56 and p53 were almost absent from parathyroid tissues. All carcinomas lacked parafibromin contrasting with invariable positivity in adenomas. Remarkable heterogeneity ofcell cycle markers and intermediate filaments must be accounted for in scientific studies and elaboration ofdiagnostic cut-offs.

Genotype of CDC73 germline mutation determines risk of parathyroid cancer.

Mutation of the CDC73 gene, which encodes parafibromin, has been linked with parathyroid cancer. However, no correlation between genotypes of germline CDC73 mutations and the risk of parathyroid cancer has been known. In this study, subjects with germline CDC73 mutations were identified from the participants of two clinical protocols at National Institutes of Health (Discovery Cohort) and from the literature (Validation Cohort). The relative risk of developing parathyroid cancer was analyzed as a function of CDC73 genotype, and the impact of representative mutations on structure of parafibromin was compared between genotype groups. A total of 419 subjects, 68 in Discovery Cohort and 351 in Validation Cohort, were included. In both cohorts, percentages of CDC73 germline mutations that predicted significant conformational disruption or loss of expression of parafibromin (referred as 'high-impact mutations') were significantly higher among the subjects with parathyroid cancers compared to all other subjects. The Kaplan-Meier analysis showed that high-impact mutations were associated with a 6.6-fold higher risk of parathyroid carcinoma compared to low-impact mutations, despite a similar risk of developing primary hyperparathyroidism between two groups. Disruption of the C-terminal domain (CTD) of parafibromin is directly involved in predisposition to parathyroid carcinoma, since only the mutations impacting this domain were associated with an increased risk of parathyroid carcinoma. Structural analysis revealed that a conserved surface structure in the CTD is universally disrupted by the mutations affecting this domain. In conclusion, high-impact germline CDC73 mutations were found to increase risk of parathyroid carcinoma by disrupting the CTD of parafibromin.

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

Parathyroid carcinoma (PC) is a rare malignant neoplasm with a relatively poor prognosis. The loss of parafibromin expression or the presence of CDC73 mutation has been found to be remarkably associated with malignancy in parathyroid tumours. However, the prognostic role of them in PC has not yet been shown due to sampling limitations. We conducted a systematic review and meta-analysis based on individual patient data to clarify the performance of parafibromin immunohistochemical staining and CDC73 gene sequencing in predicting outcomes for patients PC. Published studies from PubMed/MEDLINE, EMBASE, Cochrane and Scopus Databases were searched using the terms 'parafibromin', 'CDC73', 'HRPT2' and 'parathyroid' to identify eligible studies. From the included studies, the survival data of patients with PC were extracted, and a Cox proportional hazards model was used to assess hazard ratio (HR)fordisease-free survival (DFS) and overall survival (OS). A total of 193 patients from 9 studies were included in this survival analysis. Negative immunohistochemical staining of parafibromin was shown to be a risk factor for recurrence/metastasis (HR 2.73, P=.002) and death (HR 2.54, P=.004). Patient age≥50years was significantly related to lower OS (HR 2.37, P=.004) but not to DFS. CDC73 mutation was not statistically related to DFS or OS. Negative parafibromin staining indicated a higher risk of recurrence/metastasis and mortality. The immunohistochemical staining of parafibromin seems to be more promising in predicting outcomes for patients with PC than the sequencing of CDC73.