Histologic features of BLL.

The lymphoma is diffuse, with a starry-sky pattern due to admixed phagocytic macrophages, and is composed of medium-sized lymphoid cells showing a jigsaw puzzle effect of cytoplasmic borders. The nuclei vary in size and shape, and the mitotic rate is high (paraffin sections stained with hematoxylin and eosin; upper panels, original magnification × 40 and × 100; lower panels, × 400).