BRAF testing modalities in histiocytic disorders: Comparative analysis and proposed testing algorithm.

Area of Science:

• Oncology
• Pathology
• Genetics

Background:

• Histiocytic disorders are increasingly understood through the lens of mitogen-activated protein kinase (MAPK) pathway mutations, particularly BRAFV600E.
• The optimal diagnostic strategy for assessing BRAFV600E mutations in these disorders remains undefined.

Purpose of the Study:

• To compare the performance of different testing modalities for BRAFV600E mutation detection.
• To propose a framework for evaluating BRAFV600E mutation status in histiocytic disorders.

Main Methods:

• Retrospective review of 120 patients with histiocytic disorders who underwent BRAF mutation testing on lesional tissue.
• Evaluation of immunohistochemistry (IHC), polymerase chain reaction (PCR), and next-generation sequencing (NGS) performance.

Main Results:

• IHC demonstrated high specificity (96.4%) but moderate sensitivity (82.4%) for BRAFV600E detection when compared to NGS as the gold standard.
• False negatives with IHC were linked to low variant allele frequency or decalcified tissue; false positives were rare.
• PCR showed high concordance with NGS, with only one discordance observed among 14 patients.

Conclusions:

• IHC is a highly specific method for detecting BRAFV600E mutations but has limitations regarding false negatives and inability to detect non-BRAFV600E mutations.
• A proposed strategy involves using IHC for initial screening, followed by reflex molecular testing (PCR or NGS) for negative results to ensure comprehensive diagnostic accuracy.