One good thing in heme/onc: January 20, 2026. Langerhans Cell Histiocytosis (LCH): 5 Clinical Pearls • LCH is a rare clonal myeloid neoplasm driven by MAPK pathway activation (most commonly BRAF V600E). • Adult LCH often presents as single-system disease (bone, lung, or skin) & many patients can be managed with observation alone. • Risk-organ involvement (liver, spleen, bone marrow) predicts prognosis and guides treatment intensity. • Treatment decisions are based on disease behavior and organ i