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case_images: (A-C) Transbronchial cryobiopsy of the lung with Langerhans cell histiocytosis. At low power magnification, there are characteristic bronchiolocentric nodules with stellate appearance (A). One nodule starts to form a characteristic cyst (HE; original magnification, 100x). The marked area shows aggregates of Langerhans cells (B), which stain for CD1a by immunohistochemistry (C) (B, C; original magnification, 200x). (D, E) Evolution of imaging findings in FDG-PET/CT over time. FDG-PET at initial diagnosis of LCH (at diagnosis, D) shows increased accumulation of FDG in mediastinal lymph nodes (triangular arrow) and bone marrow (arrow), and diffusely distributed across the lungs. The post-therapy scan (13 months later, E) shows regression of the lymph nodes in size and normal FDG uptake of lymph nodes, bone marrow, and lung parenchyma.
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case_images: Histology of transbronchial cryobiopsy was consistent with LCH ( Figures 1A-C ). Finally, PET/CT scan demonstrated increased accumulation of 18F-fluorodeoxyglucose (18F-FDG) in the spleen, the lungs (diffuse), and bone marrow, and in multiple, enlarged cervical, mediastinal, and abdominopelvic lymph nodes ( Figure 1D ). PET/CT also demonstrated a near complete morphological and metabolic remission of the LCH (isolated, residual hypermetabolic cervical lymph node) ( Figure 1E ).