Lack of Association of
BRAF
Mutation With Negative
Prognostic Indicators in Papillary Thyroid Carcinoma
The University of California, San Francisco, Experience
Christopher Gouveia, MD; Nhu Thuy Can, MD; Alan Bostrom, PhD; James P. Grenert, MD, PhD;Annemieke van Zante, MD, PhD; Lisa A. Orloff, MD
IMPORTANCEPapillary thyroid carcinoma (PTC) is the most common endocrine neoplasm. B-type raf kinase (BRAF) V600E mutation has been proposed as a negative prognostic indicator in PTC, and patients harboring it should receive more aggressive initial therapy. OBJECTIVE To assess the significance ofBRAFV600E mutation in PTC in the largest US sample to date.
DESIGN We identified patients from our institution’s pathology archives diagnosed as having PTC and meeting criteria forBRAFmutation testing. Medical records were analyzed forBRAF status (positive or negative) and a list of standardized clinicopathologic features.
PARTICIPANTSA total of 429 patients with PTC at an academic medical center.
MAIN OUTCOMES AND MEASURESClinicopathologic features in patients with PTC with and withoutBRAFmutation.
RESULTS Of 429 cases with PTC, 314 (73.2%) were positive for theBRAFmutation and 115 (26.8%) tested negative.BRAFmutation was significantly associated with tumor margin positivity (P= .03) and lymph node metastasis (P= .002) on univariate analysis but not on multivariate study.BRAFmutation was a predictor of male sex (odds ratio [OR], 3.2; 95% CI, 1.4-7.2), total thyroidectomy (OR, 2.6; 95% CI, 1.1-6.2), and a negative predictor of follicular variant PTC (OR, 0.1; 95% CI, 0.1-0.4). There was no significant association betweenBRAF positivity and tumor multicentricity, lymphovascular invasion, extranodal extension, central neck involvement, advanced stage (stage III or IV), and distant metastasis.
CONCLUSIONS AND RELEVANCEBRAFV600E mutation has been extensively studied in relation to negative prognostic indicators in PTC, with no consistent relationship emerging. Two recent meta-analyses showed an overall association betweenBRAFstatus and
aggressive disease features and called for tailoring treatment plans in patients accordingly. In this, the largest US study to date,BRAFstatus was not significantly associated with most clinicopathologic features suggestive of more aggressive disease.
JAMA Otolaryngol Head Neck Surg. 2013;139(11):1164-1170. doi:10.1001/jamaoto.2013.4501 Published online September 12, 2013.
Author Affiliations:Department of Otolaryngology–Head and Neck Surgery, University of California, San Francisco, San Francisco (Gouveia, Bostrom, Orloff); Department of Otolaryngology–Head and Neck Surgery, Northwestern University, Chicago, Illinois (Gouveia); Department of Anatomic Pathology, University of California,
San Francisco, San Francisco (Can, Grenert, van Zante); Department of Pathology, University of Chicago, Chicago, Illinois (Can). Corresponding Author:Lisa A. Orloff, MD, Department of Otolaryngology–Head and Neck Surgery, University of California, San Francisco, 2380 Sutter St, Second Floor, San Francisco, CA 94115 ([email protected]).
P
apillary thyroid carcinoma (PTC) is the most common endocrine neoplasm, accounting for 88% of all thyroid malignant neoplasms.1Although treatment is oftencu-rative, there is a 15% recurrence rate over the course of 10 years, and approximately 10% of patients die as a result of disease progression.2,3Furthermore, the incidence of PTC is
increas-ing across all demographics.4
The association of B-type raf (BRAF) kinase V600E muta-tion to PTC has been extensively studied. Multiple individual publications have shown correlation ofBRAFmutation with known negative prognostic clinicopathologic features, includ-ing advanced age at diagnosis, male sex, larger tumor size, ex-trathyroidal extension, tumor multifocality, advanced TNM stage, lymph node metastasis, and recurrence.5-11In
addi-tion,BRAFmutation has been reported to be associated with overall increased mortality.12However, the results across
stud-ies have been inconsistent, and several similar large retrospec-tive trials have failed to corroborate these results.13-17The
over-all significance ofBRAFmutation in PTC therefore remains debatable.18
Two recent meta-analyses have shown an overall correla-tion ofBRAFwith extrathyroidal extension, lymph node me-tastasis, advanced TNM stage, and recurrent disease.2,19There
remains no definitive correlation betweenBRAFV600E mu-tation and the clinicopathologic features of PTC, but these stud-ies add support to the consensus thatBRAFmutation is an over-all negative prognostic indicator and cover-all for consideration of tailoring initial treatment accordingly. The usual limitations of meta-analysis, along with wide variation inBRAF muta-tion rates and heterogeneity in geographic subgroups among the included studies, restrict the translation of these results. There is a continuing need for large, nation-wide studies of the relationship betweenBRAFmutation and PTC.
The aim of this study was to summarize our institution’s experience withBRAFmutation in PTC to provide the largest US study to date. To accomplish this, we analyzed a spectrum of clinical and pathologic features in PTC tumors with and with-outBRAFV600E mutation.
Methods
This retrospective study was approved by our institutional re-view board. The Department of Pathology at the University of California, San Francisco, began routineBRAFV600E testing of all PTC tumor specimens 0.4 cm or larger in April 2009. We identified 439 patients as having hadBRAFtesting of their thy-roid specimens. We included all patients with PTC who un-derwent partial or total thyroidectomy with or without lymph node sampling or neck dissection between April 2009 and April 2012. We excluded 10 patients for the following reasons: 4 for incomplete medical records, 3 for initial pathological results that were performed at an outside hospital, 2 for unknown pri-mary tumor, and 1 for recurrent disease.
All patient medical records were reviewed forBRAF sta-tus, age, sex, type of surgery, PTC subtype, multicentricity, ex-trathyroidal extension, lymphovascular invasion, tumor mar-gin status, lymph node status (including central neck
involvement), extranodal extension, distant metastasis, and final TNM stage.
BRAF
Testing
All specimens were formalin fixed and paraffin embedded. Areas of PTC with at least 50% tumor cells were identified and circled on hematoxylin-eosin–stained slides by a pathologist. These areas were scraped from corresponding unstained slides for DNA extraction using either the QIAamp DNA Mini Kit or EZ1 automated extraction system (both, Qiagen). A portion of
BRAFexon 15 encompassing codon 600 was amplified by poly-merase chain reaction (PCR) with specific primers, and codon
Table 1. Clinicopathologic Characteristics of the 429 Patients With Papillary Thyroid Carcinoma in the Study Population
Characteristic No. (%) Age at diagnosis, y Mean (SD) [range] 46.8 (14.4) [15-84] ≥45 243 (56.6) <45 186 (43.4) Sex Male 102 (23.8) Female 327 (76.2) Procedure Total thyroidectomy 367 (85.5) Hemithyroidectomy 62 (14.5) Tumor size, cma Mean (SD) [range] 1.81 (1.25) [0.15-8.50] ≤2 293 (68.3) >2 to <4 105 (24.5) ≥4 31 (7.7) Histologic subtype Classic type 370 (86.2) Follicular variant 43 (10.0) Other 16 (3.7) Multicentric 232 (54.1) Extrathyroidal extension 73 (17.0) Lymphatic invasion 42 (9.8) Vascular invasion 25 (5.8) Lymph node involvement 167 (38.9) Extranodal extension 58 (13.5) Central neck dissection
Not performed 282 (65.7)
Positive 99 (23.1)
Negative 36 (8.4)
Level not specified 12 (2.8) Margin involvement 98 (22.8) Distant metastases 11 (2.6) TNM stageb I 206 (48.0) II 20 (4.7) III 45 (10.5) IV 45 (10.5) a
Largest tumor diameter based on either gross or microscopic measurement.
b
Based on criteria established by American Joint Cancer Committee–Union Internationale Contre le Cancer, Seventh Edition, Staging System.
Table 2. Clinicopathologic Features of Papillary Thyroid Carcinoma With and Without theBRAFV600E Mutation in 429 Patients Characteristic Mutation, No. (%) PValue Positive (n = 314) Negative (n = 115) Age at diagnosis, y ≥45 177 (72.8) 66 (27.2) .91 <45 137 (73.7) 49 (26.3) Sex Male 82 (80.4) 20 (19.6) .07 Female 232 (70.9) 95 (29.1) Procedure Total thyroidectomy 283 (77.1) 84 (22.9) <.001 Hemithyroidectomy 31 (50.0) 31 (5.0) Tumor size, cma 0 to ≤2 224 (76.5) 69 (23.5) .02 >2 to <4 72 (68.6) 33 (31.4) ≥4 18 (58.1) 13 (41.9) Histologic subtype Classic type 297 (80.3) 73 (19.7) <.001 Follicular variant 11 (25.6) 32 (74.4) Other 6 (37.5) 10 (62.5) Multicentric Yes 167 (72.0) 65 (28.0) .59 No 147 (74.5) 50 (25.5) Extrathyroidal extension Yes 60 (82.2) 13 (17.8) .06 No 254 (71.3) 102 (28.7) Lymphatic invasion Yes 34 (81.0) 8 (19.0) .27 No 280 (72.4) 107 (27.6) Vascular invasion Yes 17 (68.0) 8 (32.0) .64 No 297 (73.5) 107 (26.6)
Lymph node involvement
Yes 136 (81.4) 31 (18.6) .002 No 94 (65.7) 49 (34.3) Extranodal extension Yes 46 (79.3) 12 (20.7) .32 No 181 (72.7) 68 (27.3)
Central neck dissection
Not performed 202 (71.6) 80 (28.4) .72 Performed 100 (74.1) 35 (25.9) Positive 73 (73.7) 26 (26.3) .63 Negative 27 (75.0) 9 (25.0) Margin involvement Yes 79 (80.6) 19 (19.4) .30 No 235 (71.0) 96 (29.0) Distant metastases Yes 10 (90.9) 1 (9.1) .30 No 304 (72.7) 114 (27.3)
Advanced stage (III and IV)b
Yes 71 (78.9) 19 (21.1)
.21
No 162 (71.7) 64 (28.3)
aLargest tumor diameter based on
either gross or microscopic measurement.
bBased on criteria established by
American Joint Cancer Committee–Union Internationale Contre le Cancer, Seventh Edition, Staging System.
600 was analyzed with fluorescence-labeled hybridization probes in a real-time LightCycler 480 PCR (Roche Applied Sci-ence) melting curve assay following the protocol of Rowe et al.20A melting temperature of approximately 65°C
corre-sponds with the wild-type sequence, while melting at approxi-mately 60°C indicates the T to A transversion at nucleotide 1799 that results in the V600E mutation. This assay was validated to have sensitivity for V600E mutation detection down to a minimum of at least 25% tumor cells in the specimen.
Statistical Analysis
Associations of demographic and clinical variables withBRAF
were analyzed using Fisher exact test for nominal variables and a Mann-Whitney nonparametric test for ordinal and continu-ous variables. AllPvalues were 2-tailed, andP< .05 was con-sidered statistically significant. Variables associated withBRAF
V600E mutation atP< .10 were used in a multivariate logis-tic regression model forBRAFmutation positivity. All com-putations were performed using SAS statistical software (ver-sion 9.2).
Results
A total of 429 patients with PTC from our institution met in-clusion criteria. A total of 314 (73.2%) were positive forBRAF, and 115 (26.8%) tested negative. Results of demographic fea-tures (Table 1), univariate analysis (Table 2), and multivariate analysis (Table 3) are shown.
Demographics
There was no significant association ofBRAFmutation with pa-tient age (P= .91). A higher proportion of male patients was found to beBRAFpositive compared with female patients (80.4% vs 70.9%), but this was not significant (P= .07). On multivariate analysis, male sex was found to be a predictor of positiveBRAF
status (odds ratio [OR], 3.2; 95% CI, 1.4-7.2). Patients who under-went total thyroidectomy were more likely to test positive for
BRAFthan those who received hemithyroidectomy (77.1% v. 50.0%;P< .001), and total thyroidectomy was a significant pre-dictor ofBRAFmutation (OR, 2.6; 95% CI, 1.1-6.2).
Tumor Characteristics
Classic-type PTC was significantly associated withBRAF mu-tation (P< .001) vs follicular variant and other, less common subtypes. Follicular variant was a predictor of negative status (OR, 0.1; 95% CI, 0.1-0.4). When examining patients with clas-sic-type PTC in our population, smaller tumor size was the only clinicopathologic feature significantly associated withBRAF
V600E mutation (Table 4). There was no correlation between
BRAFmutation and tumor size (P= .15).
TheBRAFmutation-positive group had a significant as-sociation with tumor margin positivity (P= .03) and a trend to-ward increased extrathyroidal extension (P= .06). In multi-variate models, these were not significantly associated with
BRAFstatus. There was no significant association between tu-mor multicentricity (P= .59) or lymphovascular invasion with
BRAFV600E mutation (P= .27 andP= .64, respectively).
Lymph Node Features and Metastasis
BRAFstatus had no association with central neck dissection (P= .72) or with positive central compartment lymph nodes (P= .63). Lymph node metastasis was significantly associ-ated withBRAFmutation (P= .002). This association did not remain significant in multivariate analysis (OR, 1.4; 95% CI, 0.7-2.6). There was no significant relationship with
BRAFstatus and extranodal extension (P= .32). There was no significant association between distant metastasis or advanced-stage disease (stage III and IV) andBRAF
positivity.
Discussion
The significance ofBRAFmutation in the management of PTC remains unclear. Several articles have shown a signifi-cant association between poor prognostic variables and
BRAFstatus,5-12but the results are inconsistent with some
studies showing a lack thereof.13-17Despite this, 2 recent
meta-analyses2,19that showed an overall relationship
betweenBRAFmutation and high-risk features concluded that steps should be taken to modify initial treatments in
BRAF-positive patients with PTC.
Given this controversy, the purpose of our study was to pro-vide a large, single-institution sampling to evaluate the asso-ciation ofBRAFmutation and poor prognostic variables in PTC. To our knowledge, this is the largest US study examining this relationship. Our results showed a lack of association be-tweenBRAFmutation status and most clinicopathologic risk
Table 3. Multivariate Analysis of the Association ofBRAFV600E Mutation and Clinicopathologic Features of Papillary Thyroid Cancer
Characteristic Odds Ratio (95% CI) PValue Sex Male 3.2 (1.4-7.2) .06 Female 1 [Reference] Procedure Total thyroidectomy 2.6 (1.1-6.2) .32 Hemithyroidectomy 1 [Reference] Tumor size, cma 0.8 (0.7-1.1) .15 Histologic subtype
Classic type 1 [Reference]
Follicular variant 0.1 (0.1-0.4) <.001 Other 0.3 (0.1-1.3) .10 Extrathyroidal extension Yes 0.9 (0.4-2.1) .82 No 1 [Reference]
Lymph node involvement
Yes 1.4 (0.7-2.6) .36 No 1 [Reference] Margin involvement Yes 2.0 (0.9-4.4) .10 No 1 [Reference]
factors studied. Only male sex, increased rate of total thyroid-ectomy, and classic-type PTC were significantly associated with positiveBRAFstatus on multivariate analysis.
Male sex is an established poor prognostic factor in PTC19
and was found to be a predictor of positiveBRAFstatus on
mul-tivariate analysis in our study. This association is inconsis-tent with findings in prior studies, with many articles unable to establish a relationship between patient sex and the pres-ence ofBRAFmutation.6,10,12,14,15,21-23There was a significant
association betweenBRAFV600E positivity and receiving a
Table 4. Clinicopathologic Features of Classic-Type Papillary Thyroid Carcinoma With and Without theBRAF
V600E Mutation Characteristic Mutation, No. (%) PValue Positive (n = 297) Negative (n = 73) Age at diagnosis, y ≥45 165 (79.7) 42 (20.3) .79 <45 132 (81.0) 31 (19.0) Sex Male 80 (26.9) 13 (17.8) .13 Female 217 (73.1) 60 (82.2) Procedure Total thyroidectomy 268 (81.5) 61 (18.5) .09 Hemithyroidectomy 29 (70.7) 12 (29.3) Tumor size, cma 0 to ≤2 213 (82.9) 44 (17.1) .02 >2 to <4 69 (78.4) 19 (21.6) ≥4 15 (60.0) 10 (40.0) Multicentric Yes 154 (76.6) 47 (23.4) .07 No 143 (84.5) 26 (15.5) Extrathyroidal extension Yes 59 (85.5) 10 (14.5) .31 No 238 (79.1) 63 (20.9) Lymphatic invasion Yes 33 (84.6) 6 (15.4) .67 No 265 (79.8) 67 (20.2) Vascular invasion Yes 15 (78.9) 4 (21.1) .78 No 282 (80.3) 69 (19.7)
Lymph node involvement
Yes 132 (83.5) 26 (16.5) .12 No 85 (75.9) 27 (24.1) Extranodal extension Yes 44 (80.0) 11 (20.0) <.99 No 171 (80.3) 42 (19.7)
Central neck dissection
Not performed 195 (80.9) 46 (19.1) .58 Performed 97 (78.2) 27 (21.8) Positive 72 (76.6) 22 (23.4) .61 Negative 25 (83.3) 5 (16.7) Margin involvement Yes 76 (84.4) 14 (15.6) .22 No 221 (78.9) 59 (21.1) Distant metastases Yes 8 (88.9) 1 (11.1) <.99 No 289 (81.4) 66 (18.6)
Advanced stage (III and IV)b
Yes 61 (81.3) 14 (18.7)
.87
No 236 (80.0) 59 (20.0)
aLargest tumor diameter based on
either gross or microscopic measurement.
bBased on criteria established by
American Joint Cancer Committee–Union Internationale Contre le Cancer, Seventh Edition, Staging System.
total vs subtotal thyroidectomy in our patient population. The cause for this association is unclear but may be due toBRAF
mutation being associated with higher-risk fine-needle aspi-ration features or neck ultrasonographic findings that would sway a surgeon toward definitive surgery; we did not exam-ine these factors in our study. We also found a significant as-sociation betweenBRAFmutation and classic-type PTC, whereas follicular variant PTC was found to be a negative pre-dictor ofBRAFmutation status on multivariate analysis. This association betweenBRAFmutation and PTC variants is well documented and highlights the importance of classifying sub-type in the study and management of PTC.7,10,13-15,22,23We
con-ducted a separate analysis of patients with classic-type PTC only and found no significant differences from our overall study population. Our study included 59 patients with nonclassic PTC. While this could contribute to our study’s overall find-ings, it is a small percentage of our sample and is accounted for in the multivariate analysis.
There are several possible explanations for the differ-ence between our findings and those of prior studies show-ing significant association ofBRAFmutation and negative prognostic factors in PTC. We analyzed data for 429 patients, the largest study in the United States and one of the largest internationally, which could show differences vs smaller individual studies with less power.BRAF-positive patients accounted for 74% of our study population. While this is within the range of prior studies, it is on the higher end of the spectrum and likely represents a heterogeneous population. Our sample is from 1 region of the United States, in contrast with prior studies, most of which are
interna-tional. However, the patient population in our study is eth-nically diverse. Genetic, dietary, and other environmental differences have been hypothesized as accounting for dif-ferences in incidence ofBRAFmutation, although we did not analyze specific ethnic factors in this study. In the meta-analysis by Kim et al,2subgroup analysis by country and
BRAFmutation rates showed the association betweenBRAF
mutation and negative prognostic variables remained true overall but could be significantly affected by each, strength-ening our study’s findings.
Our study did not evaluate disease recurrence and mor-tality association. Papillary thyroid carcinoma is a slowly pro-gressive, often curable disease, so obtaining long-term fol-low-up data is an area in need of further study. The role and value of central neck dissection in PTC is still being investi-gated, and its relationship toBRAFmutation has been inconsistent.11,24,25Our study found no significant
associa-tion between central neck dissecassocia-tion rates or positive central neck lymph nodes withBRAFmutation status.
In conclusion, the results of the present study show little correlation betweenBRAFV600E mutation and negative prognostic indicators in PTC. If anything, the absence of
BRAFmutation may prove to be a favorable prognostic indi-cator and a basis for deescalation of therapy, such as more selective use of radioactive iodine or lymph node dissection, in patients with PTC. Such data have not yet been adequately studied. Certainly, efforts to recommend more aggressive ini-tial therapies toBRAF-positive patients with PTC should be tempered until more long-term data related to outcome are available.
ARTICLE INFORMATION
Submitted for Publication:February 27, 2013; final revision received May 16, 2013; accepted June 21, 2013.
Published Online:September 12, 2013. doi:10.1001/jamaoto.2013.4501.
Author Contributions:Dr Orloff had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design:Gouveia, Can, van Zante, Orloff.
Acquisition of data:Gouveia, Can, Grenert, van Zante, Orloff.
Analysis and interpretation of data:Gouveia, Can, Bostrom, Grenert, Orloff.
Drafting of the manuscript:Gouveia, Can, Bostrom. Critical revision of the manuscript for important intellectual content:Gouveia, Grenert, van Zante, Orloff.
Statistical analysis:Gouveia, Bostrom. Administrative, technical, or material support: Grenert, Orloff.
Study supervision:van Zante, Orloff.
Conflict of Interest Disclosures:None reported. Previous Presentation:This study was presented at the American Head and Neck Society 2013 Annual Meeting; April 11, 2013; Orlando, Florida.
REFERENCES
1. Davies L, Welch HG. Increasing incidence of thyroid cancer in the United States, 1973-2002. JAMA. 2006;295(18):2164-2167.
2. Kim TH, Park YJ, Lim JA, et al. The association of theBRAF(V600E) mutation with prognostic factors and poor clinical outcome in papillary thyroid cancer: a meta-analysis.Cancer. 2012;118(7):1764-1773.
3. Hundahl SA, Fleming ID, Fremgen AM, Menck HR. A National Cancer Data Base report on 53,856 cases of thyroid carcinoma treated in the U.S., 1985-1995.Cancer. 1998;83(12):2638-2648. 4. Chen AY, Jemal A, Ward EM. Increasing incidence of differentiated thyroid cancer in the United States, 1988-2005.Cancer.
2009;115(16):3801-3807.
5. Xing M, Westra WH, Tufano RP, et al.BRAF mutation predicts a poorer clinical prognosis for papillary thyroid cancer.J Clin Endocrinol Metab. 2005;90(12):6373-6379.
6. Yip L, Nikiforova MN, Carty SE, et al. Optimizing surgical treatment of papillary thyroid carcinoma associated withBRAFmutation.Surgery. 2009;146(6):1215-1223.
7. Xing M.BRAFmutation in thyroid cancer.Endocr Relat Cancer. 2005;12(2):245-262.
8. Lin KL, Wang OC, Zhang XH, Dai XX, Hu XQ, Qu JM. TheBRAFmutation is predictive of aggressive clinicopathological characteristics in papillary
thyroid microcarcinoma.Ann Surg Oncol. 2010;17(12):3294-3300.
9. Chakraborty A, Narkar A, Mukhopadhyaya R, Kane S, D’Cruz A, Rajan MG.BRAFV600E mutation in papillary thyroid carcinoma: significant association with node metastases and extra thyroidal invasion.Endocr Pathol. 2012;23(2):83-93.
10. Kim SJ, Lee KE, Myong JP, et al.BRAFV600E mutation is associated with tumor aggressiveness in papillary thyroid cancer.World J Surg. 2012;36(2):310-317.
11. Howell GM, Nikiforova MN, Carty SE, et al.BRAF V600E mutation independently predicts central compartment lymph node metastasis in patients with papillary thyroid cancer.Ann Surg Oncol. 2013;20(1):47-52.
12. Elisei R, Ugolini C, Viola D, et al.BRAF(V600E) mutation and outcome of patients with papillary thyroid carcinoma: a 15-year median follow-up study.J Clin Endocrinol Metab. 2008;93(10): 3943-3949.
13. Fugazzola L, Mannavola D, Cirello V, et al. BRAFmutations in an Italian cohort of thyroid cancers.Clin Endocrinol (Oxf). 2004;61(2):239-243. 14. Fugazzola L, Puxeddu E, Avenia N, et al. Correlation betweenBRAF-V600E mutation and clinico-pathologic parameters in papillary thyroid carcinoma: data from a multicentric Italian study and review of the literature.Endocr Relat Cancer. 2006;13(2):455-464.
15. Kim TY, Kim WB, Song JY, et al. TheBRAF mutation is not associated with poor prognostic factors in Korean patients with conventional papillary thyroid microcarcinoma.Clin Endocrinol (Oxf). 2005;63(5):588-593.
16. Brzeziańska E, Pastuszak-Lewandoska D, Wojciechowska K, et al. Investigation of V600E BRAFmutation in papillary thyroid carcinoma in the Polish population.Neuro Endocrinol Lett. 2007;28(4):351-359.
17. Ito Y, Yoshida H, Maruo R, et al.BRAFmutation in papillary thyroid carcinoma in a Japanese population: its lack of correlation with high-risk clinicopathological features and disease-free survival of patients.Endocr J. 2009;56(1):89-97. 18. Sipos JA, Mazzaferri EL. Thyroid cancer epidemiology and prognostic variables.Clin Oncol (R Coll Radiol). 2010;22(6):395-404.
19. Tufano RP, Teixeira GV, Bishop J, Carson KA, Xing M.BRAFmutation in papillary thyroid cancer and its value in tailoring initial treatment: a systematic review and meta-analysis.Medicine (Baltimore). 2012;91(5):274-286.
20. Rowe LR, Bentz BG, Bentz JS. Detection of BRAFV600E activating mutation in papillary thyroid carcinoma using PCR with allele-specific fluorescent probe melting curve analysis.J Clin Pathol. 2007;60(11):1211-1215.
21. Rivera M, Ricarte-Filho J, Tuttle RM, et al. Molecular, morphologic, and outcome analysis of thyroid carcinomas according to degree of extrathyroid extension.Thyroid. 2010;20(10): 1085-1093.
22. Lupi C, Giannini R, Ugolini C, et al. Association ofBRAFV600E mutation with poor
clinicopathological outcomes in 500 consecutive
cases of papillary thyroid carcinoma.J Clin Endocrinol Metab. 2007;92(11):4085-4090. 23. Ricarte-Filho J, Ganly I, Rivera M, et al. Papillary thyroid carcinomas with cervical lymph node metastases can be stratified into clinically relevant prognostic categories using oncogenicBRAF, the number of nodal metastases, and extra-nodal extension.Thyroid. 2012;22(6):575-584. 24. Paulson L, Shindo M, Schuff K, Corless C. The role of molecular markers and tumor histological type in central lymph node metastasis of papillary thyroid carcinoma.Arch Otolaryngol Head Neck Surg. 2012;138(1):44-49.
25. Shen WT, Ogawa L, Ruan D, et al. Central neck lymph node dissection for papillary thyroid cancer: comparison of complication and recurrence rates in 295 initial dissections and reoperations.Arch Surg. 2010;145(3):272-275.
