Autoimmune lymphoproliferative syndrome (ALPS), which is associated with autoimmunity and germline or somatic pathogenetic changes in genes involved in FAS-mediated apoptosis [206], has nodal or extranodal infiltrates of CD4-, CD8- T cells, which may appear as atypical medium-sized cells with clear cytoplasm that may mimic lymphoma. This evidence concerns the gene FAS and autoimmune lymphoproliferative syndrome.