CD30 and CD30 ligand (CD30L) expression in regressing lesion (LyP, patient no. 1). Immunohistochemistry on paraffin sections. (a) Typical histologic feature of LyP, type A: large, atypical blasts admixed with small, reactive lymphocytes (H&E, original magnification × 400). (b) CD30 staining is restricted to large neoplastic cells (anti-CD30, PAP method, original magnifica- tion × 400). (c) CD30L is mostly expressed by large neoplastic cells (anti-CD30L, PAP method, original magnification × 400).