PAX5 and neoplasm: In this study, 24 feline lymphomas of the nervous system growing with different anatomical patterns were submitted to phenotyping investigation by immunohistochemistry using CD20, CD79a, PAX5, and MUM-1 as B cell markers, CD3 as a T cell marker, CD56 as a marker for NK cells or T cells (19), and CD44 to mark tumor cell interaction with host tissue cells and extracellular-matrix (22).