CR2 and lymphoma: Further, bronchoscopy revealed several nodular protrusions along the trachea; Biopsy demonstrated lymphoid hyperplasia, with immunohistochemical examination showing lymphoma cells were positive for CD20, PAX-5, Bcl-2, CD21 (FDC net), CD23 (FDC net), CK (epithelium), Bcl-6 (partial), CD5 (T cell), Ki67 (+15%), but negative for CD10, CD30, Cyclin D1 and SOX11 (Figure 3).