Fig. 4

Lymphocytes infiltrated lung tissue and locally formed lymphoid follicles. A large number of small lymphocytes infiltrated in lung lesion (A HE × 100). IHC showed that the small lymphocytes were positive for CD20 (B IHC × 100). Lymphatic follicles formed in the local area of lung tissue (C HE × 200). Ki67 is highly expressed in germinal center (D IHC × 200)