Evaluation of the VE1 Antibody in Thyroid Cytology Using Ex Vivo Papillary Thyroid Carcinoma Specimens

Principles of Analytic Validation of Immunohistochemical Assays: Guideline Update

CONTEXT.—

In 2014, the College of American Pathologists developed an evidence-based guideline to address analytic validation of immunohistochemical assays. Fourteen recommendations were offered. Per the National Academy of Medicine standards for developing trustworthy guidelines, guidelines should be updated when new evidence suggests modifications.

OBJECTIVE.—

To assess evidence published since the release of the original guideline and develop updated evidence-based recommendations.

DESIGN.—

The College of American Pathologists convened an expert panel to perform a systematic review of the literature and update the original guideline recommendations using the Grading of Recommendations Assessment, Development and Evaluation approach.

RESULTS.—

Two strong recommendations, 1 conditional recommendation, and 12 good practice statements are offered in this updated guideline. They address analytic validation or verification of predictive and nonpredictive assays, and recommended revalidation procedures following changes in assay conditions.

CONCLUSIONS.—

While many of the original guideline statements remain similar, new recommendations address analytic validation of assays with distinct scoring systems, such as programmed death receptor-1 and analytic verification of US Food and Drug Administration approved/cleared assays; more specific guidance is offered for validating immunohistochemistry performed on cytology specimens.

Diagnostic Efficacy of BRAFV600E Immunocytochemistry in Thyroid Aspirates in Bethesda Category IV and Papillary Thyroid Carcinoma

Background

In papillary thyroid carcinoma (PTC), BRAFV600E is a common mutation and is associated with aggressive clinical behaviour. Immunocytochemistry (ICC) and molecular testing are recommended in the Bethesda System for Reporting Thyroid Cytopathology 2017 (TBSRTC) category III, IV and V.

Aims

The current study aimed to evaluate the diagnostic efficacy of conventional FNAC versus FNAC with BRAFV600E immunostaining in cases of TBSRTC category IV, cases of suspicious for PTC and cases of PTC.

Methods and Material

The study included a prospective case series of 45 patients with clinically palpable thyroid nodules with TBSRTC category IV, category V (suspicious for PTC) and PTC. The corresponding histology specimens of all the 45 cases were also analyzed. Immunostaining for BRAFV600E was performed on FNAC cell blocks and their corresponding histology sections using anti-BRAF (VE1) clone (Ventana). The diagnostic efficacy of the BRAFV600E immunostaining was compared on cytological specimens with histological specimens.

Results

BRAFV600E immunostaining helped to improve the sensitivity of the cytology to confirm the PTC as a diagnostic aid for thyroid FNAs. Cytology alone had a sensitivity of 62.96% and a lower specificity of 60.70%. The combination of both the tests together provided 84.62% sensitivity and much higher specificity of 100%. PPV was also increased to 100% and NPV was raised 94.12%.

Conclusions

The performance of BRAFV600E immunostaining on the cytological specimen is a rapid, simple and cost-effective test and could be considered in TBSRTC category IV and suspicious and malignant cases of PTC.

VE1 immunohistochemistry is an adjunct tool for detection of BRAFV600E mutation: Validation in thyroid cancer patients

Papillary thyroid carcinoma (PTC) is the most common endocrine malignancy among other endocrine tumors, and BRAF^V600E is a frequent genetic mutation occurring in the disease. Although different molecular techniques, most importantly sequencing has been widely recognized as a gold standard but molecular diagnosis remains an expensive, laborious, and time‐intensive process. Recently, immunohistochemistry (IHC) with anti‐BRAF V600E (VE1) antibody has increased practical utility and implemented clinically for the detection of BRAF^V600E mutation. Therefore, the study aimed to evaluate diagnostic accuracy of VE1 IHC for detecting the BRAF^V600E mutation frequency and clinical implementation in diagnostic laboratories. In this study, 72 formalin fixed paraffin‐embedded tissues (FFPE) were used to determine the BRAF^V600E mutation status using IHC and Sanger sequencing. The mutation was found in 29% and 28% cases using IHC and Sanger sequencing, respectively. Furthermore, the results showed 100% sensitivity, 98.07% specificity, 95.2% positive predictive value, and 100% negative predictive value. Notably, significant associations were found between BRAF^V600E status and tumor stage, tumor focality, and extrathyroidal extensions, respectively. VE1 IHC was found to be a highly sensitive, specific, and diagnostically accurate method in this cohort. Therefore, BRAF^V600E detection through IHC has been considered as the best tailored technique for routine pathology laboratories.

Utility of the BRAF p.V600E immunoperoxidase stain in FNA direct smears and cell block preparations from patients with thyroid carcinoma

BACKGROUND

The identification of BRAF mutations in thyroid cancer has prognostic and therapeutic implications. Although the gold standard for identifying BRAF mutations is molecular testing, the ability to perform BRAF p.V600E immunostaining on fine-needle aspiration (FNA) samples can facilitate the rapid triaging of patients to treatment options.

METHODS

A total of 50 thyroid carcinoma FNA samples, including papillary (29 samples), poorly differentiated (10 samples), anaplastic (9 samples), and Hurthle cell (2 samples) carcinomas, with a known BRAF p.V600E mutation status were selected for the current study. Immunostaining was performed on smears and cell block sections using an anti-BRAF p.V600E antibody (clone VE1). The results were compared with the known mutation status obtained by molecular testing and/or immunostaining of surgical pathology material from the same patient.

RESULTS

Of the total of 50 cases, 26 cases had smears available for the evaluation of BRAF p.V600E immunostaining; positive immunostaining was noted in 16 samples and negative immunostaining was noted in 4 samples, whereas 6 cases were equivocal. Of the 34 cases for which cell blocks were available for evaluation, BRAF p.V600E immunostaining was positive in 17 cases, negative in 16 cases, and equivocal in 1 case. The overall sensitivity and specificity of BRAF p.V600E immunostaining on the cell block preparation was 94.4% and 100%, respectively, whereas for the smears it was 80% and 63.6%, respectively.

CONCLUSIONS

BRAF p.V600E immunostaining can be performed reliably on thyroid FNA cell block preparations. However, false-positive results on direct smears limit their utility and therefore need to be interpreted with caution. Cancer Cytopathol 2018;126:406-13. © 2018 American Cancer Society.

Thyroid Fine-Needle Aspiration Cytology Practice in Korea

We reviewed the current status of thyroid fine-needle aspiration cytology (FNAC) in Korea. Thyroid aspiration biopsy was first introduced in Korea in 1977. Currently, radiologists aspirate the thyroid nodule under the guidance of ultrasonography, and cytologic interpretation is only legally approved when a cytopathologist makes the diagnosis. In 2008, eight thyroid-related societies came together to form the Korean Thyroid Association. The Korean Society for Cytopathology and the endocrine pathology study group of the Korean Society for Pathologists have been updating the cytologic diagnostic guidelines. The Bethesda System for Reporting Thyroid Cytopathology was first introduced in 2009, and has been used by up to 94% of institutions by 2016. The average diagnosis rates are as follows for each category: I (12.4%), II (57.9%), III (10.4%), IV (2.9%), V (3.7%), and VI (12.7%). The malignancy rates in surgical cases are as follows for each category: I (28.7%), II (27.8%), III (50.6%), IV (52.3%), V (90.7%), and VI (100.0%). Liquid-based cytology has been used since 2010, and it was utilized by 68% of institutions in 2016. The categorization of thyroid lesions into "atypia of undetermined significance" or "follicular lesion of undetermined significance" is necessary to draw consensus in our society. Immunocytochemistry for galectin-3 and BRAF is used. Additionally, a molecular test for BRAF in thyroid FNACs is actively used. Core biopsies were performed in only 44% of institutions. Even the institutions that perform core biopsies only perform them for less than 3% of all FNACs. However, only 5% of institutions performed core biopsies up to three times more than FNAC.

Refinement of the criteria for ultrastructural peritubular capillary basement membrane multilayering in the diagnosis of chronic active/acute antibody-mediated rejection

Chronic active/acute antibody-mediated rejection (cABMR) is the main cause of late renal allograft loss. Severe peritubular capillary basement membrane multilayering (PTCML) assessed on electron microscopy is one diagnostic feature of cABMR according to the Banff 2013 classification. We aimed to refine the PTCML criteria for an earlier diagnosis of cABMR. We retrospectively investigated ultrastructural features of 159 consecutive renal allografts and 44 nonallografts. The presence of serum donor-specific antibodies at the time of biopsy of allografts was also examined. Forty-three patients (27.0%) fulfilled the criteria of cABMR, regardless of PTCML, and comprised the cABMR group. Forty-one patients (25.8%) did not exhibit cABMR features and comprised the non-cABMR allograft control group. In addition, 15 zero-day wedge resections and 29 native kidney biopsies comprised the nonallograft control group. When the diagnostic accuracies of various PTCML features were assessed using the cABMR and non-cABMR allograft control groups, ≥4 PTCML, either circumferential or partial, in ≥2 peritubular capillaries of the three most affected capillaries exhibited the highest AUC value (0.885), greater than the Banff 2013 classification (0.640). None of the nonallograft control groups exhibited PTCML features. We suggest that ≥4 PTCML in ≥2 peritubular capillaries of the three most affected cortical capillaries represents the proper cutoff for cABMR.