Familial nonmedullary thyroid carcinoma

Thyroid cancer in adolescents and young adults

In adolescents and young adults, thyroid cancer accounts for 13% of all invasive neoplasms, being three times more frequent in females, but overdiagnosis and overtreatment are common. There are two therapeutic approaches, one radical and no longer preferred in all instances, and the other conservative. Permanent complications of surgery and metabolic irradiation can affect quality of life and carry an economic burden. The overall survival rate approaches 100% for patients with differentiated thyroid cancer regardless of the extent of treatment. Medullary thyroid carcinoma is a very different entity, occurring most frequently in the context of hereditary tumor susceptibility syndromes.

Neuroendocrine tumors and tumor syndromes in childhood

Endocrine and neuroendocrine cells form a large and diverse array of cell types. They are present in the form of specialized organs, such as the pituitary, parathyroid, thyroid, and adrenal gland, or in the form of the diffuse neuroendocrine system in the respiratory and digestive tracts. Neuroendocrine tumors are a heterogeneous group of neoplasms, yet they present certain unifying features. These include frequent hormonal overproduction that leads to specific symptoms and a typical immunohistochemical staining profile with chromogranin A and synaptophysin reactivity. Over the past decades, many neuroendocrine tumors have been described in the context of heritable tumor syndromes, and there exist several syndromes that are almost entirely composed of neuroendocrine tumors. Tumors occurring as part of these hereditary syndromes are characterized by specific genetic abnormalities that have helped our understanding of tumorigenesis, and they frequently appear at a young age. It is therefore important for the pediatric pathologist to be aware of specific histologic characteristics of neuroendocrine tumors in childhood and of their association with specific tumor syndromes. This may alert other clinicians to the possibility of multiple tumors in the patient or his family members. This review focuses on hereditary syndromes with neuroendocrine tumors, including multiple endocrine neoplasia types 1 and 2, Von Hippel-Lindau disease, neurofibromatosis type 1, Carney complex, pheochromocytoma-paraganglioma syndrome, and familial nonmedullary thyroid carcinoma. In addition, several individual neuroendocrine tumors are described, such as medullary thyroid carcinoma, gastroenteropancreatic tumors, pheochromocytoma, and paraganglioma, emphasizing specific histopathologic characteristics.

Familial nonmedullary thyroid cancer: a review of the genetics

OBJECTIVE

Thyroid cancer, the commonest of endocrine malignancies, continues to increase in incidence with over 19,000 new cases diagnosed in the European Union per year. Although nonmedullary thyroid cancer (NMTC) is mostly sporadic, evidence for a familial form, which is not associated with other Mendelian cancer syndromes (e.g., familial adenomatous polyposis and Cowden's syndrome), is well documented and thought to cause more aggressive disease. Just over a decade ago, the search for a genetic susceptibility locus for familial NMTC (FNMTC) began. This review details the genetic studies conducted thus far in the search for potential genes for FNMTC.

DESIGN

An electronic PubMed search was performed from the English literature for genetics of FNMTC and genetics of familial papillary thyroid carcinoma (subdivision of FNMTC). The references from the selected papers were reviewed to identify further studies not found in the original search criteria.

MAIN OUTCOME

Six potential regions for harboring an FNMTC gene have been identified: MNG1 (14q32), TCO (19p13.2), fPTC/PRN (1q21), NMTC1 (2q21), FTEN (8p23.1-p22), and the telomere-telomerase complex. Important genes reported to have been excluded are RET, TRK, MET, APC, PTEN, and TSHR.

CONCLUSION

The genetics of FNMTC is an exciting field in medical research that has the potential to permit individualized management of thyroid cancer. Studies thus far have been on small family groups using varying criteria for the diagnosis of FNMTC. Results have been contradictory and further large-scale genetic studies utilizing emerging molecular screening tests are warranted to elucidate the underlying genetic basis of FNMTC.

Old and new insights in the treatment of thyroid carcinoma

Thyroid cancer is the endocrine tumor that bears the highest incidence with 33 550 new cases per year. It bears an excellent prognosis with a mortality of 1530 patients per year (Jemal et al.; 2007). We have been treating patients with thyroid carcinoma during many years without many innovations. Recently, we have assisted to the development of new agents for the treatment of this disease with unexpected good results. Here we present a review with the old and new methods for the treatment of this disease.

Thyroid cancer in young adults

The incidence of thyroid cancer in young adults is rising. Differentiated carcinoma (ie, papillary, follicular, and their variants) and medullary thyroid carcinoma (MTC) represent the two most common subtypes, with differing etiologies, prognoses, and management strategies. Ultrasound (US)-guided fine needle aspiration (FNA) is the best initial test for evaluating a nodule or mass suspicious for malignancy. Tumor histology, in addition to radiographic findings and clinical presentation, guides surgical management, the need for adjuvant therapies, and the optimal approach to long-term follow-up. Radioactive iodine (RAI) is used to reduce recurrence and improve survival for differentiated thyroid carcinomas (DTCs). Emerging systemic therapies provide options for patients with progressive metastatic MTC or radio-resistant DTC. Overall, the prognosis for the most common thyroid malignancy, papillary thyroid carcinoma (PTC), is excellent. The treatment of young adult thyroid cancer patients occurs optimally as part of a multidisciplinary coordination of care.

Loss of heterozygosity at 19p13.2 and 2q21 in tumours from familial clusters of non-medullary thyroid carcinoma

Linkage studies have identified susceptibility loci for familial nonmedullary thyroid cancer (FNMTC), with and without cell oxyphilia, at chromosomal regions 19p13.2 and 2q21. There are few genetic analyses of FNMTC tumours reported at the present time and the eventual gene involved was not identified yet. The aim of this study was to assess the occurrence of loss of heterozygosity (LOH) at these loci in the tumours from familial clusters of NMTC. We have analysed LOH in 14 tumours from 9 two-case familial clusters of NMTC. Using paired blood (normal) and tumour DNA samples, we have genotyped ten microsatellite and one SNP markers throughout 19p13.2 and fourteen microsatellite markers at 2q21. Overall, eight (57%) and two (14%) out of the fourteen tumours analysed exhibited LOH at 19p13.2 and 2q21, respectively. In two families (22%), LOH for the same markers was demonstrable in the tumours of the two members of the same family. In one family (11%) LOH was demonstrable at both loci analysed. In four two-case familial clusters (44%), LOH at the 19p13.2 locus was found in only one of the tumour cases analysed. Detailed haplotype analysis showed that, in two families (22%), the pattern of LOH in tumours was consistent with selective retention of the haplotype shared by affected members. In the remaining cases, it was consistent with random allelic losses. In conclusion, we report the finding of LOH at the 19p13.2 and 2q21 loci in tumours from familial clusters of NMTC, providing evidence that inactivation of putative genes in these regions, acting as tumour-suppressors, may be involved in the development of tumours in the context of FNMTC.

Allelic variation in gene expression in thyroid tissue

Heritable allelic variation in gene expression may contribute to sporadic and familial disease, but is relatively unexplored. Papillary thyroid cancer (PTC) is characterized by strong heritability but predisposing genes have not been detected. Here we tested the hypothesis that inherited variation in allelic expression occurs in thyroid tissue and so might contribute to disease. We studied genes with a role in thyroid function, signaling, and/or tumorigenesis (PRKAR1A, DUOX1, IP3RI, ARGBP2, TPO, TG, and PEG10). We screened thyroid tissues from controls and patients with thyroid disease and lymphoblastoid cell lines from 40 healthy individuals. We demonstrated the robustness of the technique, a fluorescent dideoxy terminator-based method distinguishing the mRNA products of alleles in individuals who are heterozygous for a polymorphism in the transcript. We confirmed that the PEG10 gene transcript was derived only from one allele because of genetic imprinting. Three other genes, DUOX1, TPO, and ARGBP2 showed allelic variation in thyroid tissue and/or lymphoblastoid cells. Benign and malignant thyroid tissue from the same patient always gave concordant results. DUOX1 variation in expression was seen in 3 of 13 patients with PTC and 6 of 27 patients with benign disease. Further studies are needed to determine the significance of these and other allelic variations.

Novel germline RET mutation segregating with papillary thyroid carcinomas

The RET proto-oncogene is responsible for inherited medullary thyroid cancer syndromes. RET is also found mutated in sporadic medullary thyroid cancer (MTC) and rearranged in sporadic papillary thyroid carcinomas. Here, we describe a previously unreported germline RET mutation at codon 603 in exon 10 associated with both MTC and nonmedullary thyroid cancer (NMTC) in a kindred. RET may thus not be excluded as a potential candidate for predisposition to some forms of NMTC.

The spectrum of thyroid diseases in childhood and its evolution during transition to adulthood: natural history, diagnosis, differential diagnosis and management

In this contribution, we review current knowledge on the pathogenesis, diagnosis and differential diagnosis of thyroid disorders in childhood and adolescence, as well as present an update on therapy methods and management guidelines for these disorders. This overview is conceptually divided into two parts, one focusing on thyroid functional disorders, i.e. conditions leading to hyper- and hypothyroidism, and another one pertinent to structural abnormalities of the thyroid gland, i.e. nodular disorders and thyroid cancer. Currently, congenital hypothyroidism is diagnosed in a much more timely fashion rather than in the past, rendering hypothyroidism-related mental retardation and developmental deficits very rare in newborns and children and, hence, diminishing significantly its public health impact. At the same time, considerable advances have occurred in our understanding of the molecular basis of several genetic conditions affecting the thyroid gland in childhood, such as familial non-autoimmune hyperthyroidism, as well as of the pathways leading to thyroid neoplasia.

Papillary thyroid carcinoma associated with papillary renal neoplasia: genetic linkage analysis of a distinct heritable tumor syndrome

Papillary thyroid carcinoma usually is sporadic, but may occur in a familial form. The complete clinical and pathological phenotype of familial papillary thyroid carcinoma (fPTC) has not been determined, and the susceptibility gene(s) is unknown. We investigated the clinical and pathological characteristics of an unusually large three-generation fPTC kindred to characterize more fully the clinical phenotype. We performed linkage analysis to determine the chromosomal location of a fPTC susceptibility gene. In addition to the known association of fPTC with nodular thyroid disease, we observed the otherwise rare entity of papillary renal neoplasia (PRN) in two kindred members, one affected with PTC and the other an obligate carrier. The multifocality of PRN in one subject adds weight to the likelihood of a true genetic predisposition to PRN. Both genetic linkage and sequence analysis excluded MET, the protooncogene of isolated familial PRN, as the cause of the fPTC/PRN phenotype. A genome-wide screening and an investigation of specific candidate genes demonstrated that the fPTC/PRN phenotype was linked to 1q21. A maximum three-point log of likelihood ratio score of 3.58 was observed for markers D1S2343 and D1S2345 and for markers D1S2343 and D1S305. Critical recombination events limited the region of linkage to approximately 20 cM. A distinct inherited tumor syndrome has been characterized as the familial association of papillary thyroid cancer, nodular thyroid disease, and papillary renal neoplasia. The predisposing gene in a large kindred with this syndrome has been mapped to 1q21.

Advances in the diagnosis and management of thyroid neoplasms

Thyroid cancers are still the most common endocrine cancers. They are dominated by well-differentiated carcinomas, including papillary carcinoma, follicular carcinoma, and medullary thyroid carcinoma. Diagnosis is based on fine-needle aspiration cytologic examination. Recently, reverse transcription polymerase chain reaction for the detection of cancer-specific mRNA was shown to be a useful adjunct in both initial diagnosis and detection of recurrent disease. In addition, positron emission tomography has become a valuable tool for staging and surveillance of thyroid cancer. Given the gradual perfection of surgical technique and reduction in complication rates, near-total and total thyroidectomy should be offered to patients with well-differentiated carcinoma. For medullary thyroid carcinoma, near-total and total thyroidectomy with routine central and bilateral functional neck dissection are recommended. So far, no effective treatment exists for anaplastic thyroid carcinoma.