Histopathologic Characteristics of Thyroid Tumors Positive for BRAF V600E Mutation
Wadicar Nugent, Christopher Coyne, Marina N Nikiforova, Yuri E Nikiforov. University of Pittsburgh, Pittsburgh
Background: While large body of information has been accumulated on BRAF V600E mutation in papillary thyroid carcinoma (PTC) and its association with histopathological tumor features and a more aggressive behavior, another mutation of this gene, BRAF K601E, has not been well characterized. Herein, we report the largest to date series of BRAF K601E mutation found in thyroid nodules.
Design: Histopathologic, cytologic and molecular reports for the last five years (06/2007-06/2011) were reviewed to identify thyroid cases with various types of BRAF mutation. All case positive for BRAF K601E mutation were reviewed to confirm histopathologic diagnosis, tumor variant, and assess other features.
Results: Our analysis identified 548 tumors with BRAF mutations identified in the surgically excised of FNA samples. They included 527 (96.1%) V600E mutations, 17 (3.1%) K601E mutations, and 4 (0.8%) other BRAF mutation types. Patients with K601E positive nodules were 23-86 year old (average age, 50.3 years), with female:male ration of 3.2:1. Of those, 15 cases had surgical pathology results available for review. Fourteen (93%) of tumors positive for this mutations were papillary carcinomas, and 1 (7%) was follicular carcinoma. Excluding one case that had a complex mutation K601E+T599I, most of K601E-positive papillary carcinomas were of the follicular variant and one tumor was solid variant. Encapsulation was present in all but one case, and 5 cases showed areas of capsular or vascular invasion. Thirteen cases (86.7%) were T1 lesions, and 2 (13.3%) were T2 lesions.
Conclusions: We find that BRAF K601E mutation comprises approximately 3% of all BRAF mutations found in thyroid cancer. This mutation is strongly associated with the follicular-patterned thyroid cancer, particularly with the follicular variant of papillary carcinoma. In addition, we report for the first time the occurrence of BRAF K601E mutation in a follicular thyroid carcinoma. BRAF K601E does not appear to be as aggressive as the BRAF V600E mutation, and the majority of the tumors positive for this mutation were T1 lesions.
Tuesday, March 20, 2012 1:00 PM
Poster Session IV # 22, Tuesday Afternoon