Risk of Second Malignant Neoplasm in Familial Non-Medullary Thyroid Cancer Patients

Exploring the Susceptibility to Multiple Primary Tumors in Patients with Differentiated Thyroid Cancer

PURPOSE

It was demonstrated that differentiated thyroid cancer (DTC) patients may develop multiple primary tumors (MPT) during follow-up. Many studies showed an association between reduced telomere length and cancer phenotype; in particular, the short telomeres were associated with the development of a primary tumor. However, the role of altered telomere length in MPT development has not yet been demonstrated. The aim of this study was to evaluate the possible correlation between a short telomere length in blood leukocytes and the risk of developing MPT in DTC patients.

PATIENTS AND METHODS

We retrospectively evaluated 167 DTC patients followed up for a median of 13.6 years. Our control group was represented by 105 healthy subjects without any thyroid disease or present or past history of tumors. Our study groups, age-matched, were evaluated for the relative telomere length measured in leukocytes of peripheral venous blood.

RESULTS

The relative telomere length (RTL) was significantly different in healthy subjects compared to the total group of differentiated thyroid cancer patients [p < 0.0001]. Shorter telomeres length was observed in DTC patients with (n = 32) and without (n = 135) MPT compared to healthy subjects (p < 0.0001 and p = 0.0002, respectively). At multivariate analysis, the parameters independently associated with the presence of MPT were RTL [OR: 0.466 (0.226-0.817), p = 0.018] and the familial DTC [OR: 2.949 (1.142-8.466), p = 0.032].

CONCLUSIONS

The results of this study suggest a role of the relative telomere length in predicting MPT development in DTC patients. Our results contribute to increasing the knowledge of the genetic mechanisms underlying MPT development in DTC patients, considering relative telomere length as a possible prognostic marker.

Novel Susceptibility Genes Drive Familial Non-Medullary Thyroid Cancer in a Large Consanguineous Kindred

Familial non-medullary thyroid cancer (FNMTC) is a well-differentiated thyroid cancer (DTC) of follicular cell origin in two or more first-degree relatives. Patients typically demonstrate an autosomal dominant inheritance pattern with incomplete penetrance. While known genes and chromosomal loci account for some FNMTC, the molecular basis for most FNMTC remains elusive. To identify the variation(s) causing FNMTC in an extended consanguineous family consisting of 16 papillary thyroid carcinoma (PTC) cases, we performed whole exome sequence (WES) analysis of six family patients. We demonstrated an association of ARHGEF28, FBXW10, and SLC47A1 genes with FNMTC. The variations in these genes may affect the structures of their encoded proteins and, thus, their function. The most promising causative gene is ARHGEF28, which has high expression in the thyroid, and its protein-protein interactions (PPIs) suggest predisposition of PTC through ARHGEF28-SQSTM1-TP53 or ARHGEF28-PTCSC2-FOXE1-TP53 associations. Using DNA from a patient's thyroid malignant tissue, we analyzed the possible cooperation of somatic variations with these genes. We revealed two somatic heterozygote variations in XRCC1 and HRAS genes known to implicate thyroid cancer. Thus, the predisposition by the germline variations and a second hit by somatic variations could lead to the progression to PTC.

MEN1 in a Patient With Nonsyndromic Familial Nonmedullary Thyroid Carcinoma

Clinical syndromes involving multiple endocrine glands have been well recognized for over a century. Multiple reports describing hereditary multiple endocrine neoplasia (MEN) syndromes involving pituitary, parathyroid, and pancreatic neuroendocrine tumors have been published. Differentiated (nonmedullary) thyroid cancer can also present as a hereditary syndrome with or without a specific genetic predisposition. We report the case of a man with nonsyndromic familial nonmedullary thyroid carcinoma, a pituitary adenoma, hyperparathyroidism, an adrenal adenoma, and pancreatic adenocarcinoma. Genetic testing did not reveal mutations in the commonly reported genes associated with MEN syndromes. MEN1 is characterized by endocrine neoplasia in at least 2 of the following glands: pituitary, parathyroid, and the gastro-entero-pancreatic (GEP) tract. Co-occurrence of MEN1 with familial nonmedullary thyroid carcinoma, however, has not been reported in the medical literature. This unique case of MEN1 co-existing in a patient with nonsyndromic familial thyroid carcinoma was not associated with any common MEN syndrome germline mutations.