ALK and neoplasm: The microscopic morphologic characteristics of 5 ALK-positive DLBCL patients and 2 PBL patients were as follows: ALK-positive DLBCL, the tumor showed a sinusoidal growth pattern and was composed of monomorphic large immunoblast-like cells with round pale nuclei containing large central nuclei and abundant cytoplasm, with multinucleated neoplastic giant cells in 3 cases; PBL, the tumor showed a diffuse and cohesive proliferation of cells resembling immunoblasts and mitotic figures were observed in tumor cells.