BRAF V600E mutation in Juvenile Xanthogranuloma family neoplasms of the central nervous system (CNS-JXG): a revised diagnostic algorithm to include pediatric Erdheim-Chester disease

• Published in: Acta neuropathologica communications Vol. 7; no. 1; pp. 168 - 13
• Main Authors: Picarsic, J., Pysher, T., Zhou, H., Fluchel, M., Pettit, T., Whitehead, M., Surrey, L. F., Harding, B., Goldstein, G., Fellig, Y., Weintraub, M., Mobley, B. C., Sharples, P. M., Sulis, M. L., Diamond, E. L., Jaffe, R., Shekdar, K., Santi, M.
• Format: Journal Article
• Language: English
• Published: London BioMed Central 04.11.2019; BioMed Central Ltd; BMC
• Subjects: Algorithms; Biomedical and Life Sciences; Biomedicine; BRAF V600E; Central nervous system; Chemotherapy; Child health; CNS; Dabrafenib; Diagnosis; Future predictions; Gene mutation; Genetic aspects; Histiocytosis; Immunohistochemistry; Juvenile Xanthogranuloma; JXG; Neurology; Neurosciences; Pathology; Pediatric; Pediatric diseases; Pediatrics; Surgery; Tumors; V600E; LCH; Juvenile Xanthogranuloma; Central nervous system; ECD; JXG; CNS; Erdheim-Chester disease; Pediatric; BRAF V600E
• ISSN: 2051-5960; 2051-5960
• DOI: 10.1186/s40478-019-0811-6

The family of juvenile xanthogranuloma family neoplasms (JXG) with ERK-pathway mutations are now classified within the “L” (Langerhans) group, which includes Langerhans cell histiocytosis (LCH) and Erdheim Chester disease (ECD). Although the BRAF V600E mutation constitutes the majority of molecular alterations in ECD and LCH, only three reported JXG neoplasms, all in male pediatric patients with localized central nervous system (CNS) involvement, are known to harbor the BRAF mutation. This retrospective case series seeks to redefine the clinicopathologic spectrum of pediatric CNS-JXG family neoplasms in the post-BRAF era, with a revised diagnostic algorithm to include pediatric ECD. Twenty-two CNS-JXG family lesions were retrieved from consult files with 64% ( n  = 14) having informative BRAF V600E mutational testing (molecular and/or VE1 immunohistochemistry). Of these, 71% ( n  = 10) were pediatric cases (≤18 years) and half ( n  = 5) harbored the BRAF V600E mutation. As compared to the BRAF wild-type cohort (WT), the BRAF V600E cohort had a similar mean age at diagnosis [ BRAF  V600E: 7 years (3–12 y), vs. WT: 7.6 years (1–18 y)] but demonstrated a stronger male/female ratio ( BRAF  V600E: 4 vs WT: 0.67), and had both more multifocal CNS disease (  BRAF V600E: 80% vs WT: 20%) and systemic disease ( BRAF  V600E: 40% vs WT: none). Radiographic features of CNS-JXG varied but typically included enhancing CNS mass lesion(s) with associated white matter changes in a subset of BRAF V600E neoplasms. After clinical-radiographic correlation, pediatric ECD was diagnosed in the BRAF V600E cohort. Treatment options varied, including surgical resection, chemotherapy, and targeted therapy with BRAF-inhibitor dabrafenib in one mutated case. BRAF V600E CNS-JXG neoplasms appear associated with male gender and aggressive disease presentation including pediatric ECD. We propose a revised diagnostic algorithm for CNS-JXG that includes an initial morphologic diagnosis with a final integrated diagnosis after clinical-radiographic and molecular correlation, in order to identify cases of pediatric ECD. Future studies with long-term follow-up are required to determine if pediatric BRAF V600E positive CNS-JXG neoplasms are a distinct entity in the L-group histiocytosis category or represent an expanded pediatric spectrum of ECD.