CD44 and breast neoplasm: CD44 is recognized as a cancer stem cell marker in canine breast tumours, (Barbieri et al., 2015; Du et al., 2017; Zhou et al., 2018) and its expression is also increased in canine leukaemia, melanoma and osteosarcoma (Gelain et al., 2014; Guth et al., 2014; Milovancev et al., 2013).