The Definition of “Sizable” Blood Vessel as a Histologic Clue of Extrathyroidal Tumor Extension Can Be Clarified by Morphometric Analysis of Intra- and Extrathryroidal Blood Vessels
HyaeMin Jeon, BeomJin Lim, SoonWon Hong. Yonsei University College of Medicine, Gangnam Severance Hospital, Seoul, Republic of Korea
Background: Collage of American Pathologist cancer protocol suggests that diagnostic findings for minimal extrathyroidal extension includes the presence of carcinoma extending into perithyroidal tissues, including infiltration of adipose tissue and skeletal muscle, as well as around (and into) sizable vascular structures and nerves. However, there are no definite histological criteria of “sizable” vascular structures. Therefore, we have planned to clarify the definition of sizable vascular structures, one of the helpful histologic clues of minimal extrathyroidal extension (ETE).
Design: We hypothesized that the mean thickness of extrathyroidal arteries is significantly different from that of intrathyroidal arteries. Ten total thyroidectomy specimens with papillary carcinoma or microcarcinoma were selected by the even age and sex distribution. Representative slides of each case were analyzed. The number and the wall thickness of the arteries in intra- and extrathyroidal area were evaluated after Elastic Van Gieson (EVG) staining and using a morphometric program. In addition to the arterial wall thickness measurement, we applied immunohistochemical staining of S-100 protein to confirm the absence of nerve tissue in the thyroid parenchyma.
Results: The average numbers of extrathyroidal and intrathyroidal arteries examined in each case were 16.4 and 13.3, respectively. The mean thickness of extrathyroidal (26.9 um, range; 6.1∼137.5 um) and intrathryoidal arteries (15.1 um, range; 4.7∼58.4 um) was significantly different (p=0.000). The mean thickness of extrathryoidal and intrathyroidal arteries of male (23.5 um and 14.3 um) and female (29.8 um and 15.8 um) were not different (p=0.342 and p=0.084). In addition as we expected, we confirmed the absence of nerve tissue in the thyroid parenchyma by immunohistochemical staining of S100 protein.
Conclusions: This study showed that there is a significant difference in the thickness of extra- and intrathyroidal arterial wall. At least we can suggest that an extrathyroidal artery can be regarded as a “sizable” blood vessel when its thickness is more than 58.4 um.
Tuesday, March 20, 2012 1:00 PM
Poster Session IV # 31, Tuesday Afternoon