Response dynamics of skeletal and nodal LCH involvement sites upon PI3Kα inhibition. (A-C) panels depicting imaging data relevant to the lytic lesion in T11. (A) PET, CT, and fusion axial data layers at the level of vertebra T11 derived from PET/CT studies performed before and during systemic treatment with alpelisib. (B-C) Quantification of lesion (B) SUVmax values and (C) HU as apparent in panel A increase in 9 m; HU: P < .001. (D-G) Panels depicting imaging data relevant to the right-sided cervical lymphadenopathy. (D) PET, CT, and fusion axial data layers at the level of vertebra C1 derived from PET/CT studies performed before and during systemic treatment with alpelisib. (E-G) Quantification of lesion (E) SUVmax values, (F) HU and dimensions (G) as apparent in panel D. Abnormal FDG uptake foci in the diagnostic PET and fusion images in A and D are indicated by white arrows. CT, computed tomography; FDG, fluorodeoxyglucose; HU, Hounsfield units; PET, positron emitted tomography; SUVmax, maximum standard unit value.