Follicular Variant of Papillary Thyroid Carcinoma (FVPTC): Histological Features, BRAF Mutation, and Lymph Node Metastasis
Shikha Bose, Sambit K Mohanty, Charanjeet Singh, Amin Riley-Portuges, Wendy Sacks, Ann E Walts. Cedars-Sinai Medical Center, Los Angeles, CA; University of Minnesota, Minneapolis, MN
Background: FVPTC is currently treated the same as conventional papillary thyroid carcinoma (PTC). Recent reports indicate that well circumscribed FVPTC has a low BRAF mutation rate (similar to follicular neoplasms) whereas infiltrative FVPTC has a higher BRAF mutation rate (similar to conventional PTC) raising the possibility that histopathology and/or BRAF mutation status might help stratify FVPTC. This study aims to correlate histological features and BRAF mutation status in FVPTC with lymph node metastases.
Design: Slides of 56 FVPTC [20 with metastases to regional lymph node(s) (LNP) and 36 with negative regional lymph node(s) (LNN)] were retrieved from our files and reviewed. Patient demographics and tumor focality, size, circumscription, follicular architectural distortion, solid foci, intratumoral fibrosis, encapsulation (capsular integrity, thickness), capsular and lymphvascular invasion (LVI), extrathyroidal extension (ETE), and margin status were charted. Macrodissected formalin fixed paraffin embedded sections from 43 (20 LNP and 23 LNN) of the FVPTC were analyzed for BRAF V600E (1799T>A) mutation using real-time PCR. Correlations between the categorical variables were assessed by Fisher's exact, chi-square, and/or t-test(s) with two-sided p<0.05 considered significant.
Results: The patients (46 female, 10 male) ranged from 24 to 75 years in age (median 51 yrs). BRAF mutation was detected in 5(25%) LNP and in 7(30%) LNN FVPTC.Comparison of the LNP and the LNN groups revealed significant differences in pT-stage, tumor focality, and in the extent of circumscription, follicular architectural distortion, solid foci, papillae, LVI, and ETE. No significant difference was observed in age, gender, tumor size, intratumoral fibrosis, completeness of capsule, capsular thickness, capsular invasion, or margin status. Although BRAF mutation was detected more frequently in unencapsulated FVPTC and in cases with LVI, no significant difference was noted in the prevalence of BRAF mutation between the LNP and LNN groups.
Conclusions: -Tumor focality, circumscription, follicular architectural distortion, solid foci, papillae, LVI, ETE and pT-stage are each significant predictors of nodal involvement by FVPTC.
-In FVPTC, BRAF mutation status does not appear to correlate with lymph node metastasis.
Tuesday, March 20, 2012 1:00 PM
Poster Session IV # 24, Tuesday Afternoon