L-Type Amino Acid Transporter 1 (LAT1) Is Frequently Expressed in Thymic Carcinomas but Is Absent in Thymomas

Background: L-type amino acid transporter 1 (LAT1) has been associated With tumorgrowth and is highly expressed it) the primary human neoplasms. We investigated the significance of LAT1 expression to evaluate malignant potential in thymic epithelial tumors. Materials and Methods: Immunohistochemical Studies of 45 surgically resected thymic epithelial tumors 115 noninvasive thymomas (NT), 22 invasive thymomas (IT), and 8 thymic carcinomas (TC)] were conducted. LAT1. Ki-67 labeling index (LI). vascular endothelial growth factor (VEGF), and microvessel density of the thymic epithelial tumors were analyzed. Results: LAT1 expression for thyinornas and thymic carcinomas were 0 (0%) of 37 and 6 (75%) of eight patients, respectively. Ki-67 LI for NT, IT, and TC were 7.9 +/- 2.8%. 16.1 +/- 8.5%. and 50.6 +/- 24.4%. respectively. VEGF expression lit groups NT. IT, and TC was 0 (0%) of 15.9 (41%) of 22, and 6 (75%) of eight patients, respectively. VEGF expression was statistically associated with microvessel Count. The LAT1 expression Was statistically associated with Ki-67 LI. VEGF, and microvessel density in thymic carcinomas. Conclusion: LAT1 is frequently expressed in thymic carcinomas but is absent ill thymomas. Our results suggest that LAT1 expression might be all immunohistochemical marker for carcinomas, and could distinguished between thymomas and thymic carcinomas. J. Surg. Oncol. 2009;99:433-438. (C) 2009 Wiley-Liss, Inc.