Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features Accounts for More Than Half of "Carcinomas" Harboring RAS Mutations

BACKGROUND

Molecular testing of thyroid nodules is increasingly being utilized to guide clinical management decisions. RAS mutations are the most frequent mutations detected in the context of an indeterminate fine-needle aspiration (FNA) diagnosis. The term "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) was recently introduced to promote conservative management of tumors previously classified as noninvasive follicular variant of papillary thyroid carcinoma (FVPTC). This change in terminology was based on the indolent clinical behavior of these tumors and their molecular profile, which includes frequent RAS mutations. The aim of this study was to determine the percentage of RAS-mutant "carcinomas" that would now be classified as NIFTPs.

METHODS

A search was performed for cases with known activating RAS mutations in a database of 199 thyroid carcinomas that underwent molecular characterization as part of Profile:Oncopanel between July 2013 and July 2015. Cases of FVPTC were re-reviewed to identify tumors that now would be categorized as NIFTP. Preceding FNA diagnoses were recorded, and cases with an indeterminate FNA result (defined as a diagnosis of atypia/follicular lesion of undetermined significance, suspicious for follicular neoplasm, or suspicious for malignancy) were identified.

RESULTS

A total of 27 RAS-mutant thyroid tumors were identified. Fifteen (56%) cases had an NRAS mutation, nine (33%) had an HRAS mutation, and three (11%) had a KRAS mutation. Twenty-four (89%) cases had a preceding FNA, 19 (79%) of which had an indeterminate FNA diagnosis. The surgical resection specimen demonstrated FVPTC in 20 (74%) cases, classical type PTC in two (7%), solid variant of PTC in one (4%), and follicular thyroid carcinoma in four (15%). Of the 20 FVPTCs, 16 (80%) would now be classified as NIFTP. NIFTPs accounted for 59% of RAS-mutant carcinomas overall and 63% of RAS-mutant carcinomas with a prior indeterminate FNA diagnosis.

CONCLUSION

NIFTPs accounted for more than half of RAS-mutant "carcinomas" in this cohort. In cases where clinical and sonographic data support a low-risk phenotype, these results suggest that a lobectomy should be considered as the initial surgical approach for a nodule with an indeterminate FNA diagnosis and a RAS mutation.

Radiation-associated neoplasia: clinical, pathological and genomic correlates

Ionizing radiation is an established risk factor for the development of benign and malignant tumours. The epidemiology of radiation-associated neoplasia has been studied over the decades in diverse populations, including Japanese atomic bomb survivors, exposed communities following the Chernobyl nuclear power plant disaster, and paediatric and adult populations receiving therapeutic irradiation. Radiation has been associated with an increased risk of neoplasia throughout the human body, with some sites showing a markedly increased relative risk of developing tumours (thyroid; soft tissues), depending on patient age and the context of exposure. Although the mechanisms of cellular injury and repair resulting from ionizing radiation are well described, the genomics of radiation-induced tumours are still relatively poorly understood, with some exceptions, such as RET rearrangement in thyroid carcinomas following iodine-131 exposure and MYC amplification in cutaneous angiosarcoma following chest wall irradiation for breast cancer. This review will provide a general overview of the epidemiology, molecular mechanism, pathology and genomics of radiation-associated neoplasia in humans.

Qualifiers of atypia in the cytologic diagnosis of thyroid nodules are associated with different Afirma gene expression classifier results and clinical outcomes

BACKGROUND

Thyroid nodules with atypia of undetermined significance (AUS) on fine‐needle aspiration (FNA) have a low risk of malignancy that appears to vary based on specific features described in the AUS diagnosis. The Afirma gene expression classifier (GEC) is a molecular test designed to improve preoperative risk stratification of thyroid nodules, but its performance for different patterns of AUS has not been defined. The objective of this study was to assess GEC results and clinical outcomes in AUS nodules with architectural atypia (AUS‐A), cytologic atypia (AUS‐C) or both (AUS‐C/A).

METHODS

This was a retrospective review of all thyroid nodules with AUS cytopathology that underwent GEC testing at the authors' institution over a period of >4 years.

RESULTS

In 227 nodules that had AUS cytology results and Afirma GEC testing, the rate of benign GEC results was higher in AUS‐A nodules (70 of 107; 65%) than in AUS‐C/A nodules (25 of 65; 38%; P = .0008), and AUS‐C nodules exhibited an intermediate rate of benign results (27 of 55 nodules; 59%). The risk of cancer among patients who had GEC‐suspicious nodules, 86% of whom underwent resection, was 19% (6 of 25) for AUS‐A nodules compared with 57% (21 of 37) for AUS‐C/A nodules (P = .003) and 45% (10 of 22) for AUS‐C nodules (P = .07). In nodules that had an indeterminate repeat cytology result, no difference was observed in the rate of benign GEC results or in the malignancy rate compared with nodules that had a single cytology result.

CONCLUSIONS

The performance characteristics of Afirma GEC testing vary, depending on qualifiers of cytologic atypia. Recognition of these differences may enable clinicians to provide improved counseling and treatment recommendations to patients. Cancer Cytopathol 2017;125:313–322. © 2017 American Cancer Society.

Thyroid nodules with atypia of undetermined significance cytology and Afirma gene expression classifier (GEC) testing are analyzed based on the presence of architectural, cytologic, or both cytologic and architectural atypia. Nodules with architectural atypia are the most likely to have a benign GEC result and least likely to be malignant, suggesting that clinicians should be aware of these cytologic qualifiers when advising patients regarding GEC testing and the risk of malignancy.

Nomenclature Revision for Encapsulated Follicular Variant of Papillary Thyroid Carcinoma: A Paradigm Shift to Reduce Overtreatment of Indolent Tumors

IMPORTANCE

Although growing evidence points to highly indolent behavior of encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC), most patients with EFVPTC are treated as having conventional thyroid cancer.

OBJECTIVE

To evaluate clinical outcomes, refine diagnostic criteria, and develop a nomenclature that appropriately reflects the biological and clinical characteristics of EFVPTC.

DESIGN, SETTING, AND PARTICIPANTS

International, multidisciplinary, retrospective study of patients with thyroid nodules diagnosed as EFVPTC, including 109 patients with noninvasive EFVPTC observed for 10 to 26 years and 101 patients with invasive EFVPTC observed for 1 to 18 years. Review of digitized histologic slides collected at 13 sites in 5 countries by 24 thyroid pathologists from 7 countries. A series of teleconferences and a face-to-face conference were used to establish consensus diagnostic criteria and develop new nomenclature.

MAIN OUTCOMES AND MEASURES

Frequency of adverse outcomes, including death from disease, distant or locoregional metastases, and structural or biochemical recurrence, in patients with noninvasive and invasive EFVPTC diagnosed on the basis of a set of reproducible histopathologic criteria.

RESULTS

Consensus diagnostic criteria for EFVPTC were developed by 24 thyroid pathologists. All of the 109 patients with noninvasive EFVPTC (67 treated with only lobectomy, none received radioactive iodine ablation) were alive with no evidence of disease at final follow-up (median [range], 13 [10-26] years). An adverse event was seen in 12 of 101 (12%) of the cases of invasive EFVPTC, including 5 patients developing distant metastases, 2 of whom died of disease. Based on the outcome information for noninvasive EFVPTC, the name "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) was adopted. A simplified diagnostic nuclear scoring scheme was developed and validated, yielding a sensitivity of 98.6% (95% CI, 96.3%-99.4%), specificity of 90.1% (95% CI, 86.0%-93.1%), and overall classification accuracy of 94.3% (95% CI, 92.1%-96.0%) for NIFTP.

CONCLUSIONS AND RELEVANCE

Thyroid tumors currently diagnosed as noninvasive EFVPTC have a very low risk of adverse outcome and should be termed NIFTP. This reclassification will affect a large population of patients worldwide and result in a significant reduction in psychological and clinical consequences associated with the diagnosis of cancer.

Prevalence of Contralateral Tumors in Patients with Follicular Variant of Papillary Thyroid Cancer

BACKGROUND

Thyroid lobectomy alone is being performed increasingly for patients with encapsulated follicular variant of papillary thyroid carcinoma (fvPTC). However, the prevalence of contralateral disease in these patients is unknown. We investigated the presence of synchronous disease in fvPTC to improve decision making about the extent of surgical resection and need for surveillance.

STUDY DESIGN

We performed a retrospective review of patients who underwent thyroid surgery from October 2009 to February 2013 with a diagnosis of fvPTC as their primary lesion. We collected information on patient demographics, nodule size, multifocality, fine-needle aspiration results, lymphovascular invasion, extrathyroidal extension, and lymph node metastasis. Tumors were divided into noninvasive and invasive/infiltrative fvPTC categories. Characteristics of solitary and bilateral fvPTC were compared.

RESULTS

We identified 124 patients with final pathology demonstrating fvPTC. The most common fine-needle aspiration diagnosis was "suspicious for malignancy" (n = 53). Sixty-five contralateral tumors were identified in 44 of 124 patients (35.5%) and included fvPTC (n = 40), classical PTC (n = 22), tall cell PTC (n = 2), and follicular carcinoma (n = 1). Fifty contralateral tumors were 1 to 5 mm, 10 measured 6 to 9 mm, and 5 were ≥10 mm. Contralateral disease correlated significantly with lymphovascular invasion (p = 0.037) and larger primary lesions (p = 0.020). There was no significant difference noted in extrathyroidal extension or lymph node metastasis. Both noninvasive and invasive/infiltrative fvPTC demonstrated similar rates of contralateral disease.

CONCLUSIONS

Bilateral disease is common in fvPTC, primarily in the form of papillary microcarcinomas. Future monitoring of the contralateral lobe should be discussed with fvPTC patients who do not undergo completion thyroidectomy.

Clinical, Sonographic, and Pathological Characteristics of RAS-Positive Versus BRAF-Positive Thyroid Carcinoma

CONTEXT

Mutations in the BRAF and RAS oncogenes are responsible for most well-differentiated thyroid cancer. Yet, our clinical understanding of how BRAF-positive and RAS-positive thyroid cancers differ is incomplete.

OBJECTIVE

We correlated clinical, radiographic, and pathological findings from patients with thyroid cancer harboring a BRAF or RAS mutation.

DESIGN

Prospective cohort study.

SETTING

Academic, tertiary care hospital.

PATIENTS

A total of 101 consecutive patients with well-differentiated thyroid cancer.

MAIN OUTCOME MEASURE

We compared the clinical, sonographic, and pathological characteristics of patients with BRAF-positive cancer to those with RAS-positive cancer.

RESULTS

Of 101 patients harboring these mutations, 71 were BRAF-positive, whereas 30 were RAS-positive. Upon sonographic evaluation, RAS-positive nodules were significantly larger (P = .04), although BRAF-positive nodules were more likely to harbor concerning sonographic characteristics (hypoechogenicity [P < .001]; irregular margins [P = .04]). Cytologically, 70% of BRAF-positive nodules were classified positive for PTC, whereas 87% of RAS-positive nodules were indeterminate (P < .001). Histologically, 96% of RAS-positive PTC malignancies were follicular variants of PTC, whereas 70% of BRAF-positive malignancies were classical variants of PTC. BRAF-positive malignancies were more likely to demonstrate extrathyroidal extension (P = .003), lymphovascular invasion (P = .02), and lymph node metastasis (P < .001).

CONCLUSIONS

BRAF-positive malignant nodules most often demonstrate worrisome sonographic features and are frequently associated with positive or suspicious Bethesda cytology. In contrast, RAS-positive malignancy most often demonstrates indolent sonographic features and more commonly associates with lower risk, "indeterminate" cytology. Because BRAF and RAS mutations are the most common molecular perturbations associated with well-differentiated thyroid cancer, these findings may assist with improved preoperative risk assessment by suggesting the likely molecular profile of a thyroid cancer, even when postsurgical molecular analysis is unavailable.

Genomic Heterogeneity and Exceptional Response to Dual Pathway Inhibition in Anaplastic Thyroid Cancer

Purpose: Cancers may resist single-agent targeted therapies when the flux of cellular growth signals is shifted from one pathway to another. Blockade of multiple pathways may be necessary for effective inhibition of tumor growth. We document a case in which a patient with anaplastic thyroid carcinoma (ATC) failed to respond to either mTOR/PI3K or combined RAF/MEK inhibition but experienced a dramatic response when both drug regimens were combined.Experimental Design: Multi-region whole-exome sequencing of five diagnostic and four autopsy tumor biopsies was performed. Meta-analysis of DNA and RNA sequencing studies of ATC was performed.Results: Sequencing revealed truncal BRAF and PIK3CA mutations, which are known to activate the MAPK and PI3K/AKT pathways, respectively. Meta-analysis demonstrated 10.3% cooccurrence of MAPK and PI3K pathway alterations in ATC. These tumors display a separate transcriptional profile from other ATCs, consistent with a novel subgroup of ATC.Conclusions: BRAF and PIK3CA mutations define a distinct subset of ATC. Blockade of the MAPK and PI3K pathways appears necessary for tumor response in this subset of ATC. This identification of synergistic activity between targeted agents may inform clinical trial design in ATC. Clin Cancer Res; 23(9); 2367-73. ©2016 AACR.

Preoperative Cytologic Diagnosis of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: A Prospective Analysis

BACKGROUND

The term noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) has been proposed to replace noninvasive follicular variant of papillary thyroid carcinoma (FVPTC) in recognition of the indolent behavior of this tumor. The ability to differentiate NIFTP from classical papillary thyroid carcinoma (cPTC) by fine-needle aspiration (FNA) would facilitate conservative management for NIFTP. The aim of this study was to determine if NIFTP can be distinguished prospectively from cPTC.

METHODS

From June 2015 to January 2016, thyroid FNAs with a diagnosis of "malignant" or "suspicious for malignancy" were prospectively scored for features associated with NIFTP/FVPTC (microfollicular architecture) or cPTC (papillae, psammomatous calcifications, sheet-like architecture, and nuclear pseudoinclusions) and categorized as NIFTP/FVPTC, cPTC, or indeterminate. Results were correlated with subsequent histologic diagnoses.

RESULTS

The study included 52 patients with 56 resected nodules with a cytologic diagnosis of "malignant" (43/56) or "suspicious for malignancy" (13/56). Forty-nine patients (94%) underwent initial total thyroidectomy. Histopathologic diagnoses included 42 cPTC, 8 NIFTP, 3 invasive FVPTC, 2 follicular adenomas, and 1 poorly differentiated carcinoma. Excluding 7 indeterminate cases, 89% (8/9) of nodules classified as NIFTP/FVPTC on FNA demonstrated follicular-patterned lesions on histology (5 NIFTP, 1 invasive FVPTC, 2 follicular adenomas). Cytopathologists prospectively identified cPTC in 95% (38/40) of cases.

CONCLUSIONS

In thyroid FNAs with cytologic features concerning for PTC, NIFTP/FVPTC can be distinguished from cPTC in most cases by assessing a limited number of features. Therefore, it is both feasible and appropriate to attempt to separate NIFTP/FVPTC from cPTC on FNA to promote appropriate clinical management.

Noninvasive Follicular Variant of Papillary Thyroid Carcinoma and the Afirma Gene-Expression Classifier

BACKGROUND

It is now recognized that noninvasive follicular variant of papillary thyroid carcinoma (NFVPTC) is a distinct subset of FVPTC with an exceedingly indolent clinical course. The Afirma gene-expression classifier (GEC) helps guide clinicians in the management of thyroid nodules with indeterminate fine-needle aspiration (FNA) results. Thyroid surgery is recommended for nodules with a suspicious Afirma result, whereas observation is deemed reasonable for most nodules with a benign result. The aim of this study was to confirm that the Afirma test detects NFVPTCs and to determine how many carcinomas detected by the Afirma GEC represent NFVPTCs.

METHODS

From a database of 249 FNAs sent for Afirma testing between January 2012 and October 2014, a search was conducted for cases with a preceding FNA diagnosis of atypia/follicular lesion of undetermined significance (AUS/FLUS) or suspicious for a follicular neoplasm (SFN), a suspicious Afirma result, and a corresponding resection specimen reviewed at Brigham and Women's Hospital. The diagnoses of the prior FNAs and subsequent resection specimens were recorded. Slides for all resection specimens with a diagnosis of FVPTC were reviewed to identify NFVPTCs.

RESULTS

Sixty-three cases met the inclusion criteria. The preceding FNA diagnosis was AUS/FLUS in 34 (54%) cases and SFN in 29 (46%) cases. The surgical resection specimen demonstrated 16 (25%) FVPTCs, five (8%) follicular thyroid carcinomas, one (2%) classical type PTC, and 41 (65%) benign tumors/nodules. Of the 16 FVPTCs, 14 (88%) were NFVPTCs. Thus, NFVPTCs accounted for 64% of the carcinomas in the cohort.

CONCLUSION

These results indicate that the Afirma GEC detects NFVPTCs and that many of the carcinomas detected by Afirma are NFVPTCs. While all care should be individualized and include clinical and sonographic assessment, these results suggest lobectomy as opposed to total thyroidectomy should be considered for nodules with a preceding AUS/FLUS or SFN on cytology and a suspicious Afirma result.

Fine-needle aspiration diagnoses of noninvasive follicular variant of papillary thyroid carcinoma

OBJECTIVES

Endocrine pathologists are reconsidering whether tumors characterized as noninvasive follicular variant of papillary thyroid carcinoma (NFVPTC) warrant a diagnosis of carcinoma. A change in terminology would affect cytology diagnoses; thus, our aim was to study the preceding fine-needle aspiration (FNA) diagnoses of this group of tumors.

METHODS

We evaluated the FNA diagnoses of a primary cohort of 72 consecutively resected NFVPTCs and the cytologic and molecular features of an additional cohort of 39 tumors that included both NFVPTCs and classical papillary thyroid carcinomas (cPTCs).

RESULTS

For our primary cohort, the preceding FNA diagnosis associated with the highest risk of malignancy was suspicious for PTC in nearly half (48.6%) of cases. In contrast to the majority of cPTCs, no NFVPTCs in our second cohort had papillae or pseudoinclusions on cytologic evaluation of the FNA specimens, and none harbored a BRAF V600E mutation.

CONCLUSIONS

If NFVPTCs were no longer termed carcinomas, this would affect the rate of malignancy of FNA diagnostic categories. Cytologic and molecular features could aid in identifying NFVPTCs at the time of FNA diagnosis.

The Influence of Patient Age on Thyroid Nodule Formation, Multinodularity, and Thyroid Cancer Risk

INTRODUCTION

Although advancing age is known to influence the formation of thyroid nodules, the precise relationship remains unclear. Furthermore, it is uncertain whether age influences the risk that any thyroid nodule may prove cancerous.

AIM

The aim was to determine the impact of patient age on nodule formation, multinodularity, and risk of thyroid malignancy.

METHOD

We conducted a prospective cohort analysis of consecutive adults (ages 20-95 y) who presented for evaluation of nodular disease from 1995 to 2011. A total of 6391 patients underwent ultrasound and fine-needle aspiration of 12 115 nodules ≥ 1 cm. Patients were divided into six age groups and compared using sonographic, cytological, and histological endpoints.

RESULT

The prevalence of thyroid nodular disease increases with advancing age. The mean number of nodules at presentation increased from 1.5 in the youngest cohort (age, 20-30 y) to 2.2 in the oldest cohort (age, >70 y; P < .001), demonstrating a 1.6% annual increased risk for multinodularity (odds ratio, 1.02; P < .001). In contrast, the risk of malignancy in a newly identified nodule declined with advancing age. Thyroid cancer incidence per patient was 22.9% in the youngest cohort, but 12.6% in the oldest cohort (odds ratio, 0.972; P < .001), demonstrating a 2.2% decrease per year in the relative risk of malignancy between ages 20 and 60 years, which stabilized thereafter. Despite a lower likelihood of malignancy, identified cancers in older patients demonstrated higher risk histological phenotypes. Although nearly all malignancies in younger patients were well-differentiated, older patients were more likely to have higher risk papillary thyroid carcinoma variants, poorly differentiated cancer, or anaplastic carcinoma (P < .001).

CONCLUSION

With advancing age, the prevalence of clinically relevant thyroid nodules increases, whereas the risk that such nodules are malignant decreases. Nonetheless, when thyroid cancer is detected in older individuals, a higher-risk histological phenotype is more likely. These data provide insight into the clinical paradox that confronts physicians managing this common illness.

The Impact of Noninvasive Follicular Variant of Papillary Thyroid Carcinoma on Rates of Malignancy for Fine-Needle Aspiration Diagnostic Categories

BACKGROUND

Increased recognition of the indolent nature of noninvasive follicular variant of papillary thyroid carcinoma (NFVPTC) along with greater insight into the molecular alterations of these tumors has prompted endocrine pathologists to question whether these tumors warrant a diagnosis of carcinoma. However, a change in terminology would affect the rates of malignancy of fine-needle aspiration (FNA) diagnostic categories. Therefore, the aim of this study was to determine the percentage decrease in associated risk of malignancy for each FNA diagnostic category if NFVPTCs were no longer termed carcinomas.

METHODS

We evaluated a cohort of 655 FNAs with subsequent resection specimens over a 22-month time period. The diagnoses of the preceding FNAs were recorded according to the Bethesda System for Reporting Thyroid Cytopathology. For cases with more than one preceding FNA, the FNA diagnosis associated with the highest risk of malignancy was identified. Slides for all resection specimens with a diagnosis of FVPTC were reviewed to identify noninvasive tumors. By definition, all of these tumors were encapsulated, partially encapsulated, or well circumscribed and lacked any indication of infiltrative growth, capsular penetration, or lymphovascular invasion.

RESULTS

Our cohort of 655 FNAs with subsequent resection specimens included 53 (8.1%) nondiagnostic (ND), 167 (25.5%) benign, 97 (14.8%) atypia/follicular lesion of undetermined significance (AUS/FLUS), 88 (13.4%) suspicious for follicular neoplasm (SFN), 94 (14.4%) suspicious for malignancy (SUS), and 156 (23.8%) malignant cases (POS). Surgical resections demonstrated benign findings in 309 (47.2%) and malignant tumors in 346 (52.8%), including 85 NFVPTCs accounting for 24.6% of malignancies. Our rates of malignancy for ND, benign, AUS/FLUS, SFN, SUS, and POS were 18.9%, 13.2%, 39.2%, 45.5%, 87.2%, and 98.7%, respectively. If NFVPTC were no longer termed carcinoma, these rates would drop to 17.0% (10% decrease), 5.4% (59% decrease), 21.6% (45% decrease), 37.5% (18% decrease), 45.7% (48% decrease), and 93.6% (5% decrease), respectively.

CONCLUSION

Our findings demonstrate that if terminology were changed and NFVPTCs were not considered carcinomas, the rates of malignancy for FNA diagnostic categories would be substantially decreased, with the most clinically significant decrease seen in the SUS category, which demonstrated a relative decrease of nearly 50%.

The variable phenotype and low-risk nature of RAS-positive thyroid nodules

BACKGROUND

Oncogenic mutations are common in thyroid cancers. While the frequently detected RAS-oncogene mutations have been studied for diagnostic use in cytologically indeterminate thyroid nodules, no investigation has studied such mutations in an unselected population of thyroid nodules. No long-term study of RAS-positive thyroid nodules has been performed.

METHODS

We performed a prospective, blinded cohort study in 362 consecutive patients presenting with clinically relevant (>1 cm) thyroid nodules. Fine needle aspiration cytology and mutational testing were obtained for all nodules. Post-operative histopathology was obtained for malignant or indeterminate nodules, and benign nodules were sonographically followed. Histopathological features were compared between RAS- and BRAF-positive malignancies. RAS-positive benign nodules were analyzed for growth or cellular change from prior aspirations.

RESULTS

Overall, 17 of 362 nodules were RAS-positive. Nine separate nodules were BRAF-positive, of which eight underwent surgery and all proved malignant (100%). Out of the 17 RAS-positive nodules, ten underwent surgery, of which eight proved malignant (47%). All RAS-positive malignancies were low risk - all follicular variants of papillary carcinoma, without extrathyroidal extension, metastases, or lymphovascular invasion. RAS-positivity was associated with malignancy in younger patients (P = 0.028). Of the nine RAS-positive benign nodules, five had long-term prospective sonographic follow-up (mean 8.3 years) showing no growth or signs of malignancy. Four of these nodules also had previous aspirations (mean 5.8 years prior), all with similar benign results.

CONCLUSIONS

While RAS-oncogene mutations increase malignancy risk, these data demonstrate a low-risk phenotype for most RAS-positive cancers. Furthermore, cytologically benign, yet RAS-positive nodules behave in an indolent fashion over years. RAS-positivity alone should therefore not dictate clinical decisions.

Genomic landscape of high-grade T1 micropapillary bladder tumors

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Background: The genomic landscape of high-grade T1 micropapillary bladder tumors (HGT1micropap) is unknown. Clinically, micropapillary bladder cancer is an aggressive and possibly lethal disease. Our main objective was to assess the genomic landscape of HGT1micropap through identifying mutations, insertions/deletions (indels), translocations, and copy number variations (CNVs). Methods: We prospectively identified nine HGT1micropap with 45.4 months of median follow up. Patients were treated in a uniform manner using TUR, BCG, and appropriate follow up. We performed whole exome sequencing using Ilumina Exome _v5 plus translocation. Mutations and indels were called using the Firehose pipeline. CNVs were called using ExomeCNV. We examined the mutational landscape and compared the genomic alterations to TCGA (>T2, n=131)2 and publicly available data on non-muscle invasive bladder tumors (Ta/T1, n=37)1. Results: Within the HGT1micropap, mutations on TP53, KMT2D, TSC1, and ATM were suggested to occur more frequently compared to the NMIBC control group1. FGFR3 was seen at the expected frequency for NMIBC. The mutations of interest are presented in Table 1 with the percentage seen in the other cohorts. Of interest, TSC1 was seen in higher frequency in micropapillary than in the NMIBC or the TCGA cohort2. We did not see any patterns between CNVs and mutations. We also saw two patients with severe chromothripsis. 3 patients had loss of chromosome 9 or 9q without any other severe chromosome alterations. CNV alterations will be presented and compared to MIBC. Conclusions: In this preliminary analysis, our HGT1micropap, showed a mutational landscape more similar to MIBC compared to NMIBC bladder landscape. We did not find any clear driver of the micropapillary histology at the exome level in this limited sample of patient, which may indicate that tumor heterogeneity or epigentic changes may be driving this aggressive phenotype. [Table: see text]

HER2 as a target in invasive urothelial carcinoma

We evaluated primary tumors from two cohorts, Spain (N = 111) and Greece (N = 102), for patients who were treated with platinum-based chemotherapy. Patients were tested for HER2 status (IHC score of 3+ or FISH ratio of ≥ 2.2) by immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), DNA copy number, mRNA expression, and mutation status in patients with metastatic urothelial carcinoma (UC), and its impact on survival. ERBB2 mutation was determined by hotspot sequencing. mRNA expression was assessed using NanoString counting. Association of overall survival (OS) and HER2 status was assessed by a Cox regression model. NIH-3T3 cells containing HER2 V777L were assessed for growth, invasion, and HER2 kinase activation. In all, 22% of Spanish and 4% of Greek cohorts had 3+ HER2 staining by IHC. FISH amplification was identified in 20% of Spanish and 4% of Greek cohorts. Kappa coefficient between FISH and IHC was 0.47. HER2 status was not associated with OS in univariate (Spanish P = 0.34; Greek P = 0.11) or multivariate (Spanish P = 0.49; Greek P = 0.12) analysis. HER2-positive tumors expressed higher levels of HER2 mRNA than HER2-negative tumors (P < 0.001). HER2 mutations (V777L and L755S) were identified in two (2%) patients. In vitro analysis of V777L results in transformation of NIH-3T3 cells, leading to increased growth, invasion on soft agar, and HER2 kinase constitutive activation. In summary, HER2 overexpression or amplification in the primary tumor did not predict OS in patients with metastatic UC. HER2 positivity rates can differ between different populations. Further trials in genomically screened patients are needed to assess HER2-targeted therapies in UC.

BRAF V600E mutation-specific antibody: A review

The significance of BRAF mutations in neoplasia was first recognized in 2002 when mutations were discovered in a broad range of cancers. Numerous subsequent studies expanded our understanding of BRAF V600E as a critical diagnostic, prognostic, and predictive biomarker in many cancers. Additionally, the advent of small-molecule inhibitors of BRAF V600E rendered assessment of BRAF mutation status essential in tumors such as melanoma. In clinical practice, evaluation of BRAF mutation status has routinely been performed by DNA-based assays utilizing polymerase chain reaction (PCR). However, molecular testing is not available at many hospitals since it is time-consuming, expensive, and requires expertise in molecular techniques. The first BRAF V600E-specific antibody was reported in 2011 (clone VE1). A purified version of this antibody as well as a second monoclonal antibody targeted to BRAF V600E is now commercially available. In this review, clinicopathologic characteristics associated with BRAF-mutant tumors will be highlighted, and the prognostic and predictive implications of a BRAF V600E mutation will be discussed with a focus on melanoma, thyroid carcinoma and colorectal carcinoma. Additionally, we will review the correlation between immunohistochemistry and molecular results and deliberate how BRAF immunohistochemistry might be utilized in the evaluation of these tumors.

Reexamining treatment of high-grade T1 bladder cancer according to depth of lamina propria invasion: a prospective trial of 200 patients

BACKGROUND

Management of high-grade T1 (HGT1) bladder cancer represents a major challenge. We studied a treatment strategy according to substaging by depth of lamina propria invasion.

METHODS

In this prospective observational cohort study, patients received initial transurethral resection (TUR), mitomycin-C, and BCG. Subjects with shallower lamina propria invasion (HGT1a) were followed without further surgery, whereas subjects with HGT1b received a second TUR. Association of clinical and histological features with outcomes (primary: progression; secondary: recurrence and cancer-specific survival) was assessed using Cox regression.

RESULTS

Median age was 71 years; 89.5% were males, with 89 (44.5%) cases T1a and 111 (55.5%) T1b. At median follow-up of 71 months, disease progression was observed in 31 (15.5%) and in univariate analysis, substaging, carcinoma in situ, tumour size, and tumour pattern predicted progression. On multivariate analysis only substaging, associated carcinoma in situ, and tumour size remained significant for progression.

CONCLUSIONS

In HGT1 bladder cancer, the strategy of performing a second TUR only in T1b cases results in a global low progression rate of 15.5%. Tumours deeply invading the lamina propria (HGT1b) showed a three-fold increase in risk of progression. Substaging should be routinely evaluated, with HGT1b cases being thoroughly evaluated for cystectomy. Inclusion in the TNM system should also be carefully considered.

Poorly Differentiated Thyroid Carcinoma

Poorly differentiated thyroid carcinoma (PDTC) has been recognized for the past 30 years as an entity showing intermediate differentiation and clinical behavior between well-differentiated thyroid carcinomas (ie, papillary thyroid carcinoma and follicular thyroid carcinoma) and anaplastic thyroid carcinoma; however, there has been considerable controversy around the definition of PDTC. In this review, the evolution in the definition of PDTC, current diagnostic criteria, differential diagnoses, potentially helpful immunohistochemical studies, and molecular alterations are discussed with the aim of highlighting where the diagnosis of PDTC currently stands.

Response and acquired resistance to everolimus in anaplastic thyroid cancer

Everolimus, an inhibitor of the mammalian target of rapamycin (mTOR), is effective in treating tumors harboring alterations in the mTOR pathway. Mechanisms of resistance to everolimus remain undefined. Resistance developed in a patient with metastatic anaplastic thyroid carcinoma after an extraordinary 18-month response. Whole-exome sequencing of pretreatment and drug-resistant tumors revealed a nonsense mutation in TSC2, a negative regulator of mTOR, suggesting a mechanism for exquisite sensitivity to everolimus. The resistant tumor also harbored a mutation in MTOR that confers resistance to allosteric mTOR inhibition. The mutation remains sensitive to mTOR kinase inhibitors.

Abstract 1724: Genomic mechanisms of exquisite sensitivity and acquired resistance to everolimus in a patient with anaplastic thyroid carcinoma

Understanding genetic mechanisms of sensitivity and resistance to targeted anticancer therapies may improve patient selection and rational treatment designs. One approach to increase this understanding involves the study of exceptional responders: rare patients with unexpected exquisite sensitivity or durable responses to therapy. We identified an exceptional responder on a study of the allosteric mTOR inhibitor everolimus in thyroid cancer: a 57-yr-old woman with refractory metastatic anaplastic thyroid carcinoma (ATC), a highly aggressive neoplasm with no adequate therapies and a median survival of 5 months. After beginning treatment with everolimus, the patient experienced a near complete response that lasted for 18 months, followed by progressive disease, which was then re-biopsied. To date, mechanisms of clinical resistance to mTOR inhibition have not been described.

We performed whole exome sequencing (WES) of both pre-treatment and drug resistant tumor tissue to look for the underlying mechanisms of exquisite sensitivity and acquired resistance to everolimus. WES of the pre-treatment tumor revealed a somatic nonsense mutation in TSC2, a tumor suppressor gene whose inactivation is known to activate the mTOR pathway and result in sensitivity to mTOR inhibition in some cancers. WES of the drug resistant tumor additionally revealed a mutation in mTOR (mTOR-F2108L) not detected in the pre-treatment tumor. Structural modeling demonstrated that this mutation occurs in the FKBP12-rapamycin binding domain of mTOR and is predicted to prevent binding of the drug to the protein. Overexpressing mTOR-F2108L in HEK-293T cells resulted in significant resistance to rapamycin compared to cells expressing wild type (wt) mTOR. In cells expressing the mutant mTOR, rapamycin did not decrease phosphorylation of S6K1, a downstream target of mTOR, compared with cells expressing wt mTOR. Notably, cells expressing mTOR-F2108L remained sensitive to the direct TOR inhibitor torin, suggesting a therapeutic approach to overcome resistance in this patient.

In summary, we add ATC to the growing list of cancers found to be exquisitely sensitive to everolimus when activating mTOR pathway mutations are present. Moreover, we present the first reported, to our knowledge, mechanism of acquired resistance to everolimus identified in patients. The fact that this occurs via a binding domain mutation that blocks allosteric mTOR inhibition suggests that followup therapy with direct TOR inhibitors may still have benefit in some patients who develop resistance to everolimus. The use of precision medicine approaches in ATC to screen for alterations in the mTOR pathway may help identify subsets of patients who would benefit from targeted therapies directed against mTOR. Moreover, the use of serial biopsies to profile patients who develop resistance to everolimus could dictate optimal followup treatment in ATC and other cancers.

Citation Format: Nikhil Wagle, Brian C. Grabiner, Eliezer M. Van Allen, Ali Amin-Mansour, Scott C. Carter, Nathanael Gray, Justine A. Barletta, Scott J. Swanson, Daniel Ruan, David J. Kwiatkowski, Glenn J. Hanna, Robert I. Haddad, David Sabatini, Pasi A. Janne, Levi A. Garraway, Jochen H. Lorch. Genomic mechanisms of exquisite sensitivity and acquired resistance to everolimus in a patient with anaplastic thyroid carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1724. doi:10.1158/1538-7445.AM2014-1724