The use of BRAF V600E mutation‐specific immunohistochemistry in pediatric Langerhans cell histiocytosis

Abstract

BRAF p.V600E mutations are detected in greater than 50% of pediatric Langerhans cell histiocytosis (LCH) lesions. However, the use of mutation-specific BRAF V600E immunohistochemistry (IHC) as a surrogate for molecular testing in pediatric LCH is unknown. We tested the mutation-specific BRAF V600E monoclonal antibody (clone VE1) in formalin-fixed, paraffin-embedded LCH samples from 26 pediatric patients (14 males and 12 females, ages 7 mo-17 y) using allele-specific real-time polymerase chain reaction (PCR) with a limit of detection of 0.5% as the comparative gold standard. BRAF VE1 staining was scored for both intensity (0-3+) and percentage of immunoreactive tumor cells (0%-100%). BRAF VE1 immunoreactivity was determined using both lenient (≥1+, ≥1%) and stringent (≥2+, ≥10%) scoring criteria. Using lenient-scoring criteria, we found that the sensitivity and specificity of IHC compared with allele-specific real-time PCR were 100.0% and 18.2%, respectively. The poor specificity of lenient IHC analysis was attributable to weak, 1+ staining in both BRAF-mutated and wild-type LCH. Using stringent-scoring criteria, we found that specificity improved to 100.0% at the expense of sensitivity that decreased to 80.0%. Stringent scoring generated 3 false-negative results, but in all cases, neoplastic tissue comprised less than 5% of the stained section and/or the specimen was decalcified. In conclusion, highly sensitive molecular assays remain the gold standard for BRAF mutation analysis in LCH paraffin-embedded lesions. To avoid false-positive results, unequivocal VE1 staining of 2+ intensity in greater than or equal to 10% neoplastic histiocytes is required. However, negative VE1 results require additional studies to exclude false-negatives, and stringent-scoring criteria may not be optimal for scant or decalcified specimens.

Mutation Status and Immunohistochemical Correlation of KRAS, NRAS, and BRAF in 260 Chinese Colorectal and Gastric Cancers

“…Although many studies have shown that IHC has a good detection effect on BRAF V600E mutations ( 29 – 32 ), but there will still be a part of false positive results ( 33 , 34 ). Ballester et al ( 35 ) suggested that the highly sensitive molecular assays remain the gold standard for BRAF mutation analysis in paraffin-embedded lesions. Ehsani et al ( 36 ) used IHC to detect BRAF mutations in metastatic malignant melanoma with a false positive rate of 32%.…”

The role of macrophages in interstitial lung diseases

“…The BRAF V600E mutation may be robustly detected using immunohistochemistry using the clone VE1 on formalin-fixed paraffin-embedded tissue [64], while future diagnosis of LCH could achieved by detecting mutations in circulating DNA using liquid biopsy.…”

Descriptive Analysis of Histiocytic and Dendritic Cell Neoplasms: A Single-Institution Experience

“…However, BRAF immuno- histochemistry for BRAF V600E mutation has been reported to have low sensitivity and specificity in LCH or other histiocytic and dendritic cell neoplasms. [29][30][31] Therefore, further validation is required to elucidate the accuracy of immunohistochemistry in determining BRAF V600E mutation status in histiocytic and dendritic cell neoplasms. Our outcome analyses showed that most of the histiocytic and dendritic cell neoplasms exhibit indolent clinical behaviours.…”