A genotypic and histopathological study of a large Dutch kindred with hyperparathyroidism-jaw tumor syndrome

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.

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.

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.

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.

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.

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.

Hereditary renal cell carcinoma syndromes: diagnosis, surveillance and management

PURPOSE

Genetic factors have been implicated in the pathogenesis of renal cell carcinoma (RCC), with around 3% of cases having a family history. A greater knowledge of the genetics of inherited RCC has the potential to translate into novel therapeutic targets for sporadic RCC.

METHODS

A literature review was performed summarising the current knowledge on hereditary RCC diagnosis, surveillance and management.

RESULTS

Familial RCC is usually inherited in an autosomal dominant manner, although inherited RCC may present without a relevant family history. A number of familial RCC syndromes have been identified. Familial non-syndromic RCC is suspected when ≥ 2 relatives are affected in the absence of syndromic features, although clear diagnostic criteria are lacking. Young age at onset and bilateral/multicentric tumours are recognised characteristics which should prompt molecular genetic analysis. Surveillance in individuals at risk of inherited RCC aims to prevent morbidity and mortality via early detection of tumours. Though screening and management guidelines for some inherited RCC syndromes (e.g. von Hippel-Lindau disease, Birt-Hogg-Dube syndrome, hereditary leiomyomatosis) are well defined for rare cause of inherited RCC (e.g. germline BAP1 mutations), there is limited information regarding the lifetime RCC risks and the most appropriate screening modalities.

CONCLUSION

Increasing knowledge of the natural history and genetic basis has led to characterisation and tailored management of hereditary RCC syndromes. International data sharing of inherited RCC gene variant information may enable evidence-based improvements in the diagnosis, surveillance protocols and management of these rare conditions.

Hyperparathyroidism-jaw Tumor Syndrome Confirmed by Preoperative Genetic Testing

We herein report the case of a young woman who was diagnosed with primary hyperparathyroidism and in whom genetic testing confirmed a diagnosis of hyperparathyroidism-jaw tumor syndrome. Familial hyperparathyroidism was suspected based on the patient's young age at the onset of the disease. Thus, genetic testing was performed. It showed a germline mutation in the HRPT2/CDC73 gene and confirmed the diagnosis of hyperparathyroidism-jaw tumor syndrome. Total parathyroidectomy was performed to prevent recurrence. In patients with early-onset hyperparathyroidism, genetic testing should be considered to facilitate the selection of a proper surgical procedure based on the consideration of future life expectancy.

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.

An Overview of Autosomal Dominant Tumour Syndromes with Prominent Features in the Oral and Maxillofacial Region

Several autosomal dominant inherited tumour syndromes demonstrate prominent features in the oral and maxillofacial region. Although multiple organ systems are frequently involved, the target organs more frequently affected are the skin (nevoid basal cell carcinoma syndrome, Brooke-Spiegler syndrome, Birt-Hogg-Dube syndrome and Muir-Torre syndrome), gastrointestinal tract (Peutz-Jegher syndrome and Gardner syndrome) or endocrine system (multiple endocrine neoplasia type 2b and hyperparathyroidism-jaw tumour syndrome). In some syndromes, the disease is multisystem with skin index lesions presenting in the head and neck (Cowden syndrome and tuberous sclerosis complex). The pertinent features of these syndromes are reviewed with a systems-based approach, emphasising their clinical impact and diagnosis.

A Novel Mutation in a Patient with Hyperparathyroidism-Jaw Tumour Syndrome

Hyperparathyroidism-jaw tumour syndrome (HPT-JT) is a rare variant of familial hyperparathyroidism, characterized by primary hyperparathyroidism (PHPT) due to one or multiple parathyroid adenomas, and benign tumours of the mandible and maxilla. It has an autosomal dominant pattern of inheritance, and is associated with mutations that deactivate the cell division cycle protein 73 homolog (CDC73) gene, also known as hyperparathyroidism 2 (HRPT2), located on the long arm of chromosome 1, that encodes for the tumour suppressor protein parafibromin. In the majority of cases, PHPT is the presenting symptom, but up to 30 % of HPT-JT cases initially present with an ossifying fibroma of the maxillofacial bones. HPT-JT may result in severe hypercalcemia-related complications and an elevated risk of parathyroid carcinoma. For this reason, early identification of the disease is important. We present the case of a 23-year-old woman who was found to have jaw tumours and was later diagnosed with PHPT. Genetic analysis revealed a novel mutation in exon 1 of CDC73. This report contributes to the understanding of the genetics of this rare syndrome. It also highlights the fact that HPT-JT should be considered and CDC73 mutation analysis should be performed in cases of early-onset PHPT associated with ossifying fibromas of the jaw.

Two cases of multiple ossifying fibromas in the jaws

BACKGROUND

The clinicopathologic characteristics of multiple ossifying fibroma (OF) are unclear due to the condition's rarity, making diagnosis challenging. Sporadic multiple OFs must be distinguished from hyperparathyroidism-jaw tumour syndrome (HPT-JT) related OF and other fibro-osseous lesions.

METHODS

Multiple OF cases were identified from ossifying fibroma cases. Clinical data including age, sex, anatomic site, radiographic features, clinical impression, treatment and available follow-up data as well as serum calcium, phosphorus, and parathyroid hormone (PTH) were recorded. GNAS and HRPT2 genetic mutations were examined in the two present cases. Case reports of sporadic multiple ossifying fibroma and HPT-JT-related OF were also reviewed.

RESULTS

The two present cases were confirmed as sporadic multiple OF, with no genetic GNAS and HRPT2 mutations found. The incidence of sporadic multiple ossifying fibroma was 2.0% (2/102). The total 18 sporadic multiform OF cases were characterized as followed: 13 (72.2%) female; 5 (27.8%) male; mean age 28.6 years; 2/16 (11.1%) cases only in the mandible; 4/18 (22.2%) cases only in the maxilla; and 12/18 (66.7%) cases in both the maxilla and mandible. Radiographically, the lesions were radiolucent in 5/18 (27.8%) cases and mixed density in 13/18 (72.2%) cases. Along with 24 cases of HPT-JT related OF were reviewed, sixteen (66.7%) patients were diagnosed with a single lesion, and 8 patients (33.3%) were diagnosed with multiple jaw lesions.

CONCLUSIONS

Sporadic multiple OFs are very rare, but must be distinguished from HPT-JT related OF. We strongly recommend that patients diagnosed with multiple ossifying fibromas receive serum PTH testing and mutation screening of HRPT2.

VIRTUAL SLIDES

http://www.diagnosticpathology.diagnomx.eu/vs/1194507146115753.

Identification and functional characterization of three NoLS (nucleolar localisation signals) mutations of the CDC73 gene

Hyperparathyroidism Jaw-Tumour Syndrome (HPT-JT) is characterized by primary hyperparathyroidism (PHPT), maxillary/mandible ossifying fibromas and by parathyroid carcinoma in 15% of cases. Inactivating mutations of the tumour suppressor CDC73/HRPT2 gene have been found in HPT-JT patients and also as genetic determinants of sporadic parathyroid carcinoma/atypical adenomas and, rarely, typical adenomas, in familial PHPT. Here we report the genetic and molecular analysis of the CDC73/HRPT2 gene in three patients affected by PHPT due to atypical and typical parathyroid adenomas, in one case belonging to familial PHPT. Flag-tagged WT and mutant CDC73/HRPT2 proteins were transiently transfected in HEK293 cells and functional assays were performed in order to investigate the effect of the variants on the whole protein expression, nuclear localization and cell overgrowth induction. We identified four CDC73/HRPT2 gene mutations, three germline (c.679_680delAG, p.Val85_Val86del and p.Glu81_Pro84del), one somatic (p.Arg77Pro). In three cases the mutation was located within the Nucleolar Localisation Signals (NoLS). The three NoLS variants led to instability either of the corresponding mutated protein or mRNA or both. When transfected in HEK293 cells, NoLS mutated proteins mislocalized with a predeliction for cytoplasmic or nucleo-cytoplasmic localization and, finally, they resulted in overgrowth, consistent with a dominant negative interfering effect in the presence of the endogenous protein.

High prevalence of simple kidney cysts in patients with primary hyperparathyroidism

PTH has been demonstrated to promote renal epithelial cell proliferation and cysts development. The study aimed to evaluate the prevalence of kidney cysts in patients with primary hyperparathyroidism (PHPT). The prevalence of renal cysts diagnosed at abdominal ultrasound examinations in 172 PHPT patients (59.4+/-15.1 yr, mean age+/-SD; female/male 2.8) with preserved renal function was compared with that observed in 210 age- and sex-matched healthy controls. All patients underwent clinical, serum, and urine evaluations, and bone mineralization assessment by dual X-ray absorptiometry. Simple kidney cysts occurred with a higher prevalence in both male and female PHPT patients in comparison with healthy controls (34.9% vs 16.2% p<0.001). Kidney cysts were absent in patients younger than 39 yr, whereas they were present in one third of PHPT patients in their 4th, 5th, and 6th decades, increasing up to 45% after the age of 70. Multiple renal cysts were larger and more frequent than single cysts. PHPT patients with renal cysts were affected by a more active PTH secretion than patients without renal cysts as indicated by significant higher hypercalcemia and lower tubular maximal phosphate (TmP) reabsorption, while renal function, the occurrence of kidney stones, and osteoporosis were similar in both groups. Reduced TmP values were associated with about 3-fold increase in the risk of kidney cysts. In conclusion, simple renal cysts might be considered as a benign kidney complication of PHPT and might be related to the action of the chronic elevated PTH levels on tubular epithelial cells.

Benign fibro-osseous lesions of the craniofacial complex. A review

Benign fibro-osseous lesions of the craniofacial complex are represented by a variety of disease processes that are characterized by pathologic ossifications and calcifications in association with a hypercellular fibroblastic marrow element. The current classification includes neoplasms, developmental dysplastic lesions and inflammatory/reactive processes. The definitive diagnosis can rarely be rendered on the basis of histopathologic features alone; rather, procurement of a final diagnosis is usually dependent upon assessment of microscopic, clinical and imaging features together. Fibrous dysplasia and osteitis deformans constitute two dysplastic lesions in which mutations have been uncovered. Other dysplastic bone diseases of the craniofacial complex include florid osseous dysplasia, focal cemento-osseous dysplasia and periapical cemental dysplasia, all showing a predilection for African descent individuals; although no specific genetic alterations in DNA coding have yet to be uncovered and most studies have been derived from predominant high African descent populations. Ossifying fibromas are neoplastic lesions with four subtypes varying with regard to behavior and propensity for recurrence after surgical excision. The clinicopathologic and molecular features of this unique yet heterogeneous group of diseases are reviewed.

Immunohistochemical assessment of parafibromin in mouse and human tissues

Parafibromin is a protein encoded by the HRPT2 oncosuppressor gene, whose mutation causes the hyperparathyroidism-jaw tumour syndrome, characterized by the occurrence of parathyroid adenoma or carcinoma, fibro-osseous jaw tumours, and renal neoplastic and non-neoplastic abnormalities. Non-morphological techniques, such as Northern and Western blotting and reverse transcriptase-PCR, indicate that parafibromin is ubiquitously expressed, but extensive immunohistochemical studies have not been performed. To increase our knowledge of the distribution and patterns of expression of parafibromin, we examined its expression and location in many different mouse and human organs by immunohistochemistry. There were no substantial differences in parafibromin expression between mouse and human. We found widespread expression of parafibromin, except in connective tissue, smooth muscle, endothelium and some other types of epithelia (colonic, urinary, tubaric, uterine, thyroid). Heterogeneity of positivity intensity and subcellular location (nuclear, nucleocytoplasmic, cytoplasmic) was found between tissues and cell types, suggesting differential functional involvement of parafibromin. Moreover, higher parafibromin expression was found in cell types, such as hepatocytes, cells of the base of gastric glands, renal cortex tubules and the pars intermedia of the hypophysis, which are characterized by different proliferative capacity, thus indicating that the cellular function of parafibromin may not be reduced only to its anti-proliferative effect.

HRPT2 mutations are associated with malignancy in sporadic parathyroid tumours

BACKGROUND

Hyperparathyroidism is a common endocrinopathy characterised by the formation of parathyroid tumours. In this study, we determine the role of the recently identified gene, HRPT2, in parathyroid tumorigenesis.

METHODS

Mutation analysis of HRPT2 was undertaken in 60 parathyroid tumours: five HPT-JT, three FIHP, three MEN 1, one MEN 2A, 25 sporadic adenomas, 17 hyperplastic glands, two lithium associated tumours, and four sporadic carcinomas. Loss of heterozygosity at 1q24-32 was performed on a subset of these tumours.

RESULTS

HRPT2 somatic mutations were detected in four of four sporadic parathyroid carcinoma samples, and germline mutations were found in five of five HPT-JT parathyroid tumours (two families) and two parathyroid tumours from one FIHP family. One HPT-JT tumour with germline mutation also harboured a somatic mutation. In total, seven novel and one previously reported mutation were identified. "Two-hits" (double mutations or one mutation and loss of heterozygosity at 1q24-32) affecting HRPT2 were found in two sporadic carcinomas, two HPT-JT-related and two FIHP related tumours.

CONCLUSIONS

The results in this study support the role of HRPT2 as a tumour suppressor gene in sporadic parathyroid carcinoma, and provide further evidence for HRPT2 as the causative gene in HPT-JT, and a subset of FIHP. In light of the strong association between mutations of HRPT2 and sporadic parathyroid carcinoma demonstrated in this study, it is hypothesised that HRPT2 mutation is an early event that may lead to parathyroid malignancy and suggest intragenic mutation of HRPT2 as a marker of malignant potential in both familial and sporadic parathyroid tumours.

Familial adult renal neoplasia

Our understanding of the molecular mechanisms underlying the tumorigenesis of renal cell carcinoma (RCC) has partially come from studies of RCC related familial cancer syndromes such as von Hippel-Lindau (VHL) disease and hereditary papillary RCC (HPRC). These studies have led to the identification of RCC related genes, which, besides allowing accurate diagnosis of these diseases, have been found mutated or abnormally expressed in the sporadic counterparts of these familial renal tumours. To date, a number of renal tumour related syndromes have been described. We review recent advances in this field and discuss a genetic approach to managing familial cases of renal tumours occasionally encountered by cancer geneticists and urologists.