Tonsillar p16-Positive Follicular Dendritic Cell Sarcoma Mimicking HPV-Related Oropharyngeal Squamous Cell Carcinoma: A Case Report and Review of Reported Cases.

Follicular dendritic cell sarcoma (FDCS) is a rare entity which can share morphologic features with non-keratinizing squamous cell carcinoma. Recent reports suggest that up to half of FDCSs show immunohistochemical positivity for p16 (Zhang et al., in Hum Pathol 66:40-47, 2017), a stain that is conventionally used in the risk stratification of oropharyngeal squamous cell carcinoma (OPSCC). Herein, we report a case of p16-positive FDCS with clinical and histomorphologic overlap with human papilloma virus (HPV)-related OPSCC.

Independent clonal origins of distinct tumor foci in multifocal papillary thyroid carcinoma.

BACKGROUND: Papillary thyroid carcinoma is frequently multifocal. We investigated whether noncontiguous tumor foci arise from intraglandular metastases from a single primary tumor or originate as unrelated clones derived from independent precursors. METHODS: Using a polymerase-chain-reaction assay involving the human androgen receptor gene (HUMARA), we analyzed the patterns of X-chromosome inactivation of multiple distinct foci of well-differentiated multifocal papillary thyroid cancer from 17 women. RESULTS: Multiple thyroid tumor foci from 10 of 17 patients yielded DNA of adequate quality and were heterozygous for the HUMARA polymorphism and hence suitable for analysis. A single X chromosome was inactivated in each focus, consistent with its monoclonality. When the specific monoclonal configurations of each patient's discrete tumor foci were compared, discordant patterns indicative of independent origins were observed among the tumors from five patients; results in the remaining five were consistent with either a shared or independent clonal origin. CONCLUSIONS: Individual tumor foci in patients with multifocal papillary thyroid cancer often arise as independent tumors.

Somatic and germ-line mutations of the HRPT2 gene in sporadic parathyroid carcinoma.

BACKGROUND: We looked for mutations of the HRPT2 gene, which encodes the parafibromin protein, in sporadic parathyroid carcinoma because germ-line inactivating HRPT2 mutations have been found in a type of familial hyperparathyroidism--hyperparathyroidism-jaw tumor (HPT-JT) syndrome--that carries an increased risk of parathyroid cancer. METHODS: We directly sequenced the full coding and flanking splice-junctional regions of the HRPT2 gene in 21 parathyroid carcinomas from 15 patients who had no known family history of primary hyperparathyroidism or the HPT-JT syndrome at presentation. We also sought to confirm the somatic nature of the identified mutations and tested the carcinomas for tumor-specific loss of heterozygosity at HRPT2. RESULTS: Parathyroid carcinomas from 10 of the 15 patients had HRPT2 mutations, all of which were predicted to inactivate the encoded parafibromin protein. Two distinct HRPT2 mutations were found in tumors from five patients, and biallelic inactivation as a result of a mutation and loss of heterozygosity was found in one tumor. At least one HRPT2 mutation was demonstrably somatic in carcinomas from six patients. Unexpectedly, HRPT2 mutations in the parathyroid carcinomas of three patients were identified as germ-line mutations. CONCLUSIONS: Sporadic parathyroid carcinomas frequently have HRPT2 mutations that are likely to be of pathogenetic importance. Certain patients with apparently sporadic parathyroid carcinoma carry germ-line mutations in HRPT2 and may have the HPT-JT syndrome or a phenotypic variant.

Surveillance for early detection of aggressive parathyroid disease: carcinoma and atypical adenoma in familial isolated hyperparathyroidism associated with a germline HRPT2 mutation.

UNLABELLED: Familial hyperparathyroid syndromes involving mutations of HRPT2 (also CDC73), a tumor suppressor, are important to identify because the relatively high incidence of parathyroid malignancy associated with such mutations warrants a specific surveillance strategy. However, there is a dearth of reports describing experience with surveillance and early detection informed by genetic insight into this disorder. INTRODUCTION: Familial isolated hyperparathyroidism (FIHP) is a rare cause of parathyroid (PT) tumors without other neoplasms or endocrinopathies. Germline mutations in CASR, MEN1, and rarely, HRPT2 have been identified in kindreds with FIHP. HRPT2 mutations may be enriched in FIHP families with PT carcinoma, underscoring the importance of identifying causative mutations. MATERIALS AND METHODS: A 13-year-old boy, whose father had died of PT carcinoma, developed primary hyperparathyroidism. A left superior PT mass was identified by ultrasonography and removed surgically. Aggressive histological features of the boy's tumor included fibrous trabeculae, mitoses, and microscopic capsular infiltration. Two years later, under close biochemical surveillance, primary hyperparathyroidism recurred 5 months after documentation of normocalcemia and normal parathyroid status. Ultrasound and MRI identified a newly enlarged right superior PT gland but indicated no recurrent disease in the left neck. Histologic features typical of a benign adenoma were evident after surgical extirpation of the gland. RESULTS: Leukocyte DNA analysis revealed a frameshift mutation in exon 2 of HRPT2. The initial tumor manifested the expected germline HRPT2 mutation, plus a distinct somatic frameshift mutation, consistent with the Knudson "two hit" concept of biallelic inactivation of a classic tumor suppressor gene. Genetic screening of the patient's 7 asymptomatic and previously normocalcemic siblings revealed three with the same germline HRPT2 mutation. One of the siblings newly identified as mutation-positive was noted to be hypercalcemic at the time of the genetic screening. He was found to have a PT adenoma with aggressive features. Two of the five children of another mutation-positive sibling also carry the same HRPT2 mutation. CONCLUSIONS: Despite the reported rarity of HRPT2 mutations in FIHP, a personal or family history of PT carcinoma in FIHP mandates serious consideration of germline HRPT2 mutation status. This information can be used in diagnostic and management considerations, leading to early detection and removal of potentially malignant parathyroid tumors.

HRPT2 mutational analysis of typical sporadic parathyroid adenomas.

CONTEXT: Mutations of HRPT2 are frequent in sporadic parathyroid carcinomas and central to their pathogenesis. However, the potential diagnostic utility of HRPT2 mutation status to distinguish between parathyroid carcinoma and adenoma hinges on the frequency of HRPT2 mutations in benign adenomas. Even a low rate of HRPT2 mutation in adenomas would greatly alter diagnostic specificity, because adenomas are far more prevalent than carcinomas. The issue remains open because of the limited number of typical adenomas, not subjected to additional selection criteria, examined in previous studies. OBJECTIVE/DESIGN/PATIENTS: To determine the frequency of HRPT2 somatic mutations in a substantial series of typical, sporadic parathyroid adenomas, we directly sequenced coding and flanking splice junctional regions of all HRPT2 exons in solitary adenomas from 60 patients. RESULTS/CONCLUSIONS: No intragenic HRPT2 mutations were detected, strengthening the degree of specificity of HRPT2 mutation as a feature of sporadic parathyroid carcinoma as opposed to sporadic adenomas. Our observations encourage additional study of the diagnostic potential of HRPT2 in parathyroid neoplasia and support the view that HRPT2 inactivation is not an important participant in the pathogenesis of typical parathyroid adenomas.

Molecular pathogenesis of primary hyperparathyroidism.

This article will primarily focus on the molecular pathogenesis of common, sporadic (nonfamilial) parathyroid adenomas; two genes currently have established roles in the development of these tumors. The cyclin D1/PRAD1 gene was identified as a clonally activated oncogene in parathyroid adenomas and has subsequently been established as a major contributor to human neoplasia. Overexpression of cyclin D1, a key regulator of the cell cycle, has been implicated in the pathogenesis of 20-40% of sporadic parathyroid adenomas. That such cyclin D1 overexpression indeed constitutes a stimulus to excessive parathyroid cell proliferation has been confirmed experimentally by the development of a transgenic mouse model with parathyroid-targeted overexpression of cyclin D1. Parathyroid hormone (PTH)-cyclin D1 transgenic mice develop parathyroid hypercellularity, biochemical hyperparathyroidism, and a shifted in vivo parathyroid-calcium setpoint; these mice constitute an animal model of human hyperparathyroidism in which aspects of tumorigenesis, parathyroid secretory setpoint control, and the pathophysiology of the chronic hyperparathyroid state can be further investigated. The MEN1 tumor suppressor is the only other gene to date with an established role in the pathogenesis of sporadic parathyroid adenomatosis. Specific clonal alterations involving somatic mutation and/or deletion of both MEN1 alleles have been demonstrated in about 15-20% of sporadic parathyroid adenomas. Allelic losses on 11q occur in roughly twice this number of adenomas, raising the still-unresolved possibility that an additional tumor suppressor gene on 11q may be the functional target of many of these acquired deletions. A mouse model of MEN1 deficiency causes a phenotype that includes parathyroid hypercellularity albeit unaccompanied by biochemical hyperparathyroidism, and additional mouse models in which menin deficiency is targeted to the parathyroids will likely provide additional important insights. The MEN1 gene product menin may have a role in transcriptional regulation involving JunD; several other menin-interacting proteins have also been identified. The in vivo mechanism of menin's actions, with special attention to its role as a parathyroid oncosuppressor, will be important to establish, as will the potential interrelationships between these pathways and those involving cyclin D1. A number of genes, put forth as candidate tumor suppressors based on their genomic locations, roles in familial disease, and/or other relevant biological functions, have been examined for pathogenetic mutations in sporadic parathyroid tumors with negative results; these include the calcium-sensing receptor protein (CaR), vitamin-D receptor (VDR), and RET. However, the CaR, which when partially or markedly deficient because of germline mutation can cause familial hypocalciuric hypercalcemia or neonatal severe hyperparathyroidism, must still be considered as having a potentially important secondary role in the manifestations of sporadic parathyroid tumors. Future goals include identifying additional parathyroid oncogenes and tumor suppressor genes; exploiting tools of complex trait genetics to ascertain whether development of "sporadic" hyperparathyroidism might be influenced by predisposing polymorphic alleles in the population; obtaining molecular insights into the relationship between proliferative and hormone regulatory abnormalities of hyperparathyroidism; and obtaining molecular insights into the observed association of parathyroid neoplasia with exposure to ionizing irradiation and with the postmenopausal state.

Mutational analysis of Smad3, a candidate tumor suppressor implicated in TGF-beta and menin pathways, in parathyroid adenomas and enteropancreatic endocrine tumors.

Based upon molecular allelotyping and comparative genomic hybridization studies, chromosome 15q is the likely location of a tumor suppressor gene important in the pathogeneses of sporadic enteropancreatic endocrine tumors and parathyroid adenomas. Interest has focused on Smad3 as a candidate endocrine tumor suppressor gene because 1) it is localized to 15q and 2) it encodes a TGF beta signaling molecule that has been identified as a binding partner of the multiple endocrine neoplasm type 1 gene product menin, itself involved in enteropancreatic and parathyroid neoplasia. To determine whether Smad3 plays a primary role in development of these tumors, 20 enteropancreatic tumors and 67 parathyroid adenomas were investigated for loss of heterozygosity at DNA markers surrounding Smad3. Twenty percent of enteropancreatic tumors and 24% of parathyroid adenomas showed loss. All 9 coding exons and intron-exon boundaries of the Smad3 gene were then sequenced in genomic DNA from all 20 enteropancreatic and 25 parathyroid tumors, including every case with loss of heterozygosity. No acquired clonal mutations, insertions, or microdeletions in Smad3 were detected in any tumors. Because inactivating somatic mutation is the hallmark of an authentic tumor suppressor, Smad3 is unlikely to function as a classical tumor suppressor gene in the pathogenesis of sporadic parathyroid or enteropancreatic endocrine tumors.

Mutational analyses of RB and BRCA2 as candidate tumour suppressor genes in parathyroid carcinoma.

OBJECTIVE: Strong evidence indicates that at least one key tumour suppressor gene important for the development of malignant parathyroid tumours is located on chromosome 13, but the critical target gene remains unknown. Importantly, the region of acquired DNA loss includes two established tumour suppressor genes, the retinoblastoma gene, RB (RB1) and BRCA2. Resolution of whether RB or BRCA2 is the critical 13q tumour suppressor gene in parathyroid cancer requires analysis of these genes' sequences for intragenic inactivating mutations. Therefore, RB and BRCA2 were analysed in a group of parathyroid carcinomas in which mutations of these genes should be most readily detectable. PATIENTS AND DESIGN: Six parathyroid carcinomas from four patients which showed loss of heterozygosity (LOH) at the RB locus and/or 13q loss by comparative genomic hybridazation (CGH) were selected from a CGH/LOH-screened panel of 16 carcinoma specimens from 10 patients. These tumours were examined for mutations by direct sequencing of the complete 27-exon coding region, intron-exon boundaries and promoter of RB. The 26 coding exons and intron-exon boundaries of BRCA2 were also directly sequenced in seven parathyroid carcinomas with loss in the BRCA2 region. RESULTS: No microdeletions, insertions, or point mutations were detected in either RB or BRCA2 in any of the carcinomas. CONCLUSION: The absence of tumour-specific somatic mutations in RB and BRCA2 suggests that they are unlikely to act as classic tumour suppressor genes in the pathogenesis of parathyroid carcinomas. While decreased expression of these genes might contribute to parathyroid carcinomatosis in a secondary fashion and 13q loss warrants further study as a diagnostic marker for parathyroid carcinoma, the putative 13q tumour suppressor awaits identification.