Endocrine Abstracts

Introduction: Thyroid follicular adenomas (FA) and adenomatous nodules (AN) – lesions frequently found in areas with iodine deficiency, can be normo-/hypofunctioning (scintigraphically cold – SCN) or hyperfunctioning (scintigraphically hot – SHN) nodules.

Aim: Evaluation of proliferation potential in thyroid nodules on tissue samples obtained at surgery from euthyroid patients clinically diagnosed with SCN and from patients with thyroid hyperfunction and SHN.

Material and methods: We investigated the proliferation activity estimated by assessing PCNA and Ki-67 proliferation markers in 20 SCN (8 FA, 12 AN) and 16 toxic nodules (6 hyperfunctioning FA, 10 toxic multinodular goiters), on formalin-fixed, paraffin-embedded tissue samples, 4–5 μ thick; we used the LSAB immunohistochemical technique (DAB visualization) with anti-PCNA (PC10) and anti-Ki-67 (MIB-1) monoclonal antibodies. We calculated the proliferation index PI-PCNA and PI-Ki67. The data were statistically evaluated using the t-unpaired test.

Results: PI-PCNA was higher in thyroid nodules than in normal surrounding thyroid tissue, with statistically significant values for FA (14.3 vs 3.8%; P<0.029) and for AN (8.3 vs 1.24%; P<0.001). Mean PI-Ki67 in nodules versus surrounding tissue was 1.64 vs 1.10% in FA (P<0.35) and 1.07 vs 0.51% in AN (P>0.05). We also noted: (1) significantly higher PI-PCNA values (P<0.01) in FA (14.03%) than in AN (8.36%), as compared to statistically insignificant values for Ki-67 (1.64 vs 1.07%; P>0.05); (2) increased proliferation rate (P<0.01) in thyroid nodules with aspects of lymphocitic thyroiditis (LT) (PI-Ki67 was 1.21%) as compared to nodules without LT (PI-Ki67 was 0.12%); (3) a mean PI-PCNA of 8.5% and PI-Ki-67 of 4.61% in toxic thyroid nodules (TTN) versus 3.01 and 1.5% in normal surrounding thyroid, respectively.

Conclusions: The clinical expression of SCN is the consequence of increased thyrocyte proliferation in the nodules; the increased proliferative potential of TTN thyrocytes is a common feature of nodules, independent of their hystopathological characteristics.