[539] Platelet Derived Growth Factor Receptor Beta (PDGFR) Is Widely Expressed in Thyroid Neoplasms of Both C-Cell and Follicular Origin

MD Williams, MA Luna, NL Busaidy, GL Clayman. University of Texas, M.D. Anderson Cancer Center, Houston, TX

Background: Platelet derived growth factor receptor beta (PDGFR) is targeted by multiple tyrosine kinase inhibitors (such as sorafenib and sunitinib) currently in clinical trials for thyroid cancer and other tumors. However, the frequency and pattern of PDGFR expression in tumors of follicular or c-cell origin are not well characterized. We sought to examine the incidence of PDGFR in thyroid tumor cells by immunohistochemical analysis to determine which subsets of thyroid neoplasms may benefit from these targeted agents.
Design: Fifty-seven thyroid tumors including 14 medullary carcinomas, 4 anaplastic carcinomas, 14 papillary carcinomas, 21 follicular carcinomas, and 4 adenomas comprised two tissue microarrays. Expression of PDGFR was evaluated on 4 micron thick paraffin sections by immunohistochemical evaluation (sc-339, Santa Cruz Biotechnology, Inc., 1:50 dilution) performed on the Bond Automated Immunohistochemistry System. Intensity of tumor staining was graded from absent (0) to weak (1+), moderate (2+), or intense (3+). Distribution of expression within the tumor cells and within the tumor was documented.
Results: All 57 tumors expressed at least weak (1+) PDGFR expression in primarily a diffuse pattern (>80% tumor staining) in a cytoplasmic distribution with nuclear staining also noted. Pure membranous staining was not identified. Expression patterns observed were: medullary thyroid carcinomas 10 (71%) with high expression (2-3+) and 4 with low expression (1+); anaplastic carcinomas 3 (75%) with high expression and 1 with low expression; papillary carcinomas 9 (64%) with high expression and 5 with low expression; follicular carcinomas 16 (76%) with high expression and 5 with low expression; and adenomas 1 (25%) with high expression and 3 with low expression. Overall high expression (2-3+ staining) of PDGFR was noted in 39 (68%) of the 57 tumors.
Conclusions: 1) PDGFR is widely expressed in tumors of follicular or c-cell origin. 2) The receptor expression pattern is predominantly diffuse cytoplasmic with high expression (2 to 3+) within tumor cells. 3) The presence of PDGFR suggests a possible target for tyrosine kinase inhibitors for the spectrum of thyroid neoplasms.
Category: Endocrine

Tuesday, March 10, 2009 1:00 PM

Poster Session IV # 88, Tuesday Afternoon