OP63 – Follicular Variant Papillary Thyroid Microcarcinoma: Does Size Correlate with Aggressive Features?

      Hennessy, Max1; Goldenberg, David2; Warrick, Josh3 1 Medical Student, Penn State College of Medicine, Hershey, PA, United States 2 Department of Otolaryngology – Head and Neck Surgery, Penn State Health, Hershey, PA, United States 3 Department of Pathology, Penn State Health, Hershey, PA, United States   Background/Purpose: The behavior of papillary thyroid microcarcinomas (nodules ? 1cm) and follicular variant papillary thyroid cancer (FVPTC) are highly-debated topics, particularly in light of the recent reclassification of a subset of FVPTC as a benign entity. The purpose of this study was to evaluate and compare the prevalence of aggressive features in papillary thyroid cancer (PTC), papillary thyroid microcarcinomas (mPTC), FVPTC, and follicular variant papillary thyroid microcarcinoma (mFVPTC). Methods: A comprehensive chart review was conducted for all patients undergoing thyroidectomy at our institution from 2000-2012.  In total, 181 PTC, 96 mPTC, 68 FVPTC, and 44 mFVPTC patients were identified. Data on high risk features was gathered and analysis was performed using the Fisher exact test. Results: The findings indicate mPTC spreads to regional lymph nodes at a lower rate than PTC (p<0.05).  FVPTC is also less likely to metastasize to regional lymph nodes than PTC (p<0.001).  mFVPTC, however, has a similar nodal metastasis rate to both FVPTC and mPTC.  PTC was more likely to recur than mPTC (p<0.01) and FVPTC (p<0.05). We found no difference in recurrence between FVPTC versus mFVPTC or mPTC versus mFVPTC.    Discussion and Conclusion: This is the first institutional study to demonstrate that mFVPTC metastasizes to regional lymph nodes and recurs at comparable rates to both FVPTC and mPTC.  This finding is in contrast to 1998-2010 SEER data1 that suggests mPTC is twice as likely as mFVPTC to metastasis to regional nodes.   References:
    1. Singhal S, Sippel RS, Chen H, Schneider DF. Distinguishing Classical Papillary Thyroid Microcancers From Follicular-Variant Microcancers. The Journal of surgical research. 2014;190(1):151-156. doi:10.1016/j.jss.2014.03.032.


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