BM intrasinusoidal infiltration pattern in different SL entities. (A) SMZL: mixed nodular and intrasinusoidal infiltration. (B) SDRPSBCL: neoplastic cells are exclusively lodged inside the dilated sinusoids. (C) T-LGL: subtle intrasinusoidal and interstitial infiltration. (D) HSTL: highly atypical large neoplastic cells engulf the BM sinusoids. (A-B) Anti-CD20 immunostaining using the streptavidin-biotin-peroxidase complex and 3–3′-diaminobenzidine (brown signal). (C-D) Anti-CD3 immunostaining using the streptavidin-biotin-peroxidase complex and 3–3′-diaminobenzidine (brown signal). (A-D) Original magnification ×200. Images were captured by a Leica DM 3000 optical microscope, Leica DFC 320 digital camera, and Leica IM50 software.