Histologic changes--Late lesions: Healing can lead to scar, and both active, cellular lesions as well as scarred ones may be present in the same biopsy. Image A shows a cavity with a scarred wall (left) connected to cavities with cellular walls. The pleura lies at the top. Lesions like this one predispose to pneumothorax, a complication of Langerhans' cell histiocytosis. Inflammatory destruction of cavity walls (upper right) and air trapping in the cavities are probable mechanisms. Note the preservation of alveolar architecture around the active lesion (lower middle) and the destruction of alveolar walls (paracicatricial emphysema) around the scarred one (bottom left).

A

Image B shows a late, stellate scar with pericicatricial emphysema. Two lymphoid aggregates are present at the bottom. The cells in the scar did not stain with the CD1a stain, and at this stage, the diagnosis can only be suspected, but not confirmed, histologically.

B

Clinical summary Discussion

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