Response dynamics of pulmonary LCH involvement sites upon PI3Kα inhibition. (A) PET, CT, and fusion axial data layers at the level of the lungs were derived from PET/CT studies performed before and during systemic treatment with alpelisib. (B) Quantification of lesion SUVmax values as apparent in panel A. Abnormal FDG uptake in multiple lung nodules on the diagnostic PET image (white arrows). CT, computed tomography; FDG, fluorodeoxyglucose; PET, positron emitted tomography; SUVmax, maximum standard unit value.