Primary central nervous system lymphoma (PCNSL) is characterized by perivascular growth of large atypical lymphoid cells. With continued proliferation, the distribution becomes more diffuse and sheet-like. The angiocentric growth of lymphoid cells is often accompanied by perivascular reticulin deposits in a concentric fashion as shown here. Image courtesy of: Dr. Luciano de Souza Queiroz, Dept. of Pathology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, São Paulo State, BRAZIL.