The genetic instability of loss of heterozygosity (LOH) and microsatellite instability (MSI) in thyroid tumorigenesis is significant not only in chromosomal region 3p21.3, where it is important in the early stages, but also in 1p31.2 and 11p15.5 regions, where it is highly alternated in advanced stages of thyroid carcinoma.

Analysis of LOH/MSI co-occurrence in several loci, i.e., the overall frequency of allelic loss (OFAL), revealed increased OFAL in follicular adenoma (FA) and follicular thyroid carcinoma (FTC) specimens when compared with nodular goiter (NG) or papillary thyroid carcinoma (PTC), so can be treated as a hallmark of the follicular phenotype and as a promising biomarker to distinguish FA and FTC from NG and PTC.

The observed correlation of OFAL with advanced tumor stage, reflected as larger tumor diameter, higher T stage, and lymph node involvement at diagnosis, suggests OFAL may be considered a putative maker of tumor progression.