The expression of c-MYC, Cyclin D1 and Ki-67/MIB-1 in benign and malignant thyroid tissues: is there any diagnostic value?

Aim: To investigate the immunohistochemical (IHC) expression and the diagnostic value of c-MYC, Cyclin D1, and Ki-67∕MIB-1 in follicular adenomas (FAs), follicular carcinomas (FCs), and anaplastic carcinomas (ACs) of the thyroid gland, as well as in their corresponding adjacent, non-neoplastic thyroid tissue (NNTT).

Materials and methods: We conducted a retrospective study of patients who were pathologically diagnosed with FA, FC, or AC after total thyroidectomy. Tissue microarrays with cores taken from neoplastic and adjacent NNTT were constructed. Immunohistochemistry for anti-c-MYC, anti-Cyclin D1, and anti-Ki-67∕MIB-1 antibodies was performed, and the positivity was evaluated.

Results: Twenty-eight specimens were included. Nuclear c-MYC positivity was observed in 4∕11 FCs, and 3∕4 ACs, whereas cytoplasmic c-MYC positivity was found in 16∕24 NNTTs. Globally, there were statistically significant differences between neoplasms and NNTTs, with higher nuclear c-MYC and Cyclin D1 expression observed in neoplasms (p=0.017 and p=0.001, respectively). In contrast, cytoplasmic positivity was seen solely in NNTTs (p=0.001). Cyclin D1 positivity was noted in 11∕13 FAs, 7∕11 FCs, 2∕4 ATCs, and only in one NNTT. A statistically significant correlation was found between MIB1 and c-MYC nuclear positivity (p=0.040).

Conclusions: Our findings exhibit a clear difference in the IHC expression of c-MYC and Cyclin D1 between different types of thyroid tumors, as well as between the neoplastic and NNTT. Nuclear c-MYC positivity excludes the benign nature of a thyroid lesion, in contrast to cytoplasmic positivity, which demonstrates normal or hyperplastic nature.