A Greek family with a follicular variant of familial papillary thyroid carcinoma: TCO, MNG1, fPTC/PRN, and NMTC1 excluded as susceptibility loci

Abstract

The familial form of nonmedullary thyroid carcinoma (FNMTC) has been recognized as a distinct clinical entity and is characterized by multifocality and a more severe phenotype than its sporadic counterpart. The majority of FNMTC pedigrees are small in size, show variable modes of inheritance, and may present with a variety of additional benign thyroid disorders. The existence of marked phenotypic differences between FNMTC families suggests that there is genetic heterogeneity. Recent studies have mapped a susceptibility locus for FNMTC at 2q21. This locus appears particular relevant to families with at least one case of the follicular variant of papillary thyroid cancer (fvPTC). We describe the clinical and pathologic characteristics of a large three-generation fPTC kindred, with two of the four PTC patients presented with the follicular variant of PTC. It is of interest the occurrence of PTC in three siblings within a period of 3 years. In addition, multinodular goiter (MNG) was diagnosed in seven individuals, lymphocytic thyroiditis in four, while one diagnosed with a benign adenoma. From the PTC patients, one had MNG and fvPTC, one MNG, lymphocytic thyroiditis and papillary pattern of PTC, one lymphocytic thyroiditis and fvPTC, and one MNG and papillary pattern of PTC. The inheritance pattern was autosomal dominant with incomplete penetrance and women were affected more frequently than men. Considering all PTC-affected individuals, the limit of detection (LOD) score we got for this family on 2q21 was 0.5. The low LOD score is caused by a PTC patient who does not share the affected haplotype, suggesting that maybe a new locus for PTC predisposition is present in this kindred. Linkage analysis also excluded TCO, MNG, and fPTC/PRN as susceptibility loci to FNMTC in this family.