Fig. 2
Histological examination and immunohistochemical staining of thymus. The thymus tissue was polycystic, and hyperplastic small lymphocytes had diffusely infiltrated the thymus tissue (A HE × 50). Immunohistochemistry (IHC) showed that hyperplastic small lymphocytes were positive for CD20 (B IHC × 50). Lymphoepithelial lesions (C HE × 200; D, HE × 400). IHC showed positive for CK5/6 in Hassall’s corpuscles and the thymic epithelium (E IHC × 200). IHC showed that mononuclear-like B cells invading the epithelium were positive for CD20 (F IHC × 200)