Morphologic and immunophenotypic features of FDC sarcomas. A-F. Case No. 1: A and D show classic morphology of FDC sarcoma/tumor. Individual tumor cells have ovoid nuclei and vesicular chromatin. They tend to grow as fascicles in a whirling pattern. Note occasional multinucleated cells (D). D2-40 is strongly and diffusely positive in tumor cells (B, E). CD21 show focal weak positivity (C, F). G-I. Case No. 2: Marked nuclear pleomorphism and high mitotic count are seen in this case. D2-40 (H) and CD21 (I) are strongly and diffusely positive in tumor cells. D2-40 and CD21 reveal a vague whirling pattern (Original magnification: A-C, ×100; D-I, ×400).