The definition of minimal extrathyroid extension in thyroid pathology by analyzing sizable intra- and extrathyroid blood vessels

Background: To define the exact boundary of the intrathyroid and extrathyroid aspects of a gland when determining the extent of cancer invasion, we plan to clarify the definition of sizable vascular structures, which is one of the helpful histologic clues in determining a minimal extrathyroid extension. We hypothesized that arterial wall thicknesses in extrathyroid soft tissue would be significantly different from the arteries in the thyroid parenchyma. Methods: Twenty cases of papillary carcinoma were selected. The numbers and wall thicknesses of the arteries and arterioles in intrathyroid and extrathyroid tissue were evaluated. The absence of nerve tissue in the thyroid gland was confirmed using the S-100 protein immunohistochemical stain. Results: The comparison of the mean thicknesses of the total arteries between the extrathyroid and intrathyroid tissues in the retrospective study (26.88 μm vs. 15.07 μm, respectively) and the prospective study (35.24 μm vs. 16.52 μm, respectively) revealed significant differences (p=0.000). The greatest thickness of the intrathyroid arteries was 67.93 μm. Conclusions: According to our results, the study showed that the extrathyroidal arteries were significantly thicker than the intrathyroidal arteries. We suggest that the sizable blood vessels of extrathyroidal arteries should be greater than 67.93 μm in thickness.