BRAF V600E mutations are not an oncogenic driver of solitary xanthogranuloma and reticulohistiocytoma: Testing may be useful in screening for Erdheim-Chester disease.

BRAF V600E is the predominant oncogenic driver of L-group histiocytoses, which includes Erdheim-Chester disease (ECD); however, limited data exist on the prevalence of this mutation in sporadic XG family lesions. This study sought to determine the incidence of BRAF V600E mutation in a clinically annotated cohort of patients with xanthogranulomas (XG) and reticulohistiocytomas (RH). A retrospective review of 58 lesions was performed, including 41 XG and 17 RH. Immunohistochemistry (HC) and PCR-based methods were performed to evaluate for the BRAF V600E mutation. The BRAF V600E mutation was detected by IHC/PCR in 3 RH from an adult who had no history of arthritis, malignancy, xanthelasma, diabetes insipidus or bone pain. All other XG and RH were negative for the BRAF V600E mutation. No associated systemic diseases were identified in this cohort. Our findings suggest that BRAF V600E mutations are not an oncogenic driver of sporadic XG and solitary RH. Therefore, identification of such a mutation in a patient with multiple lesions should raise consideration for ECD. We also report the first known BRAF V600E mutation in a patient with multiple reticulohistiocytomas.