CCR6 and neoplasm: When ductal epithelial growth was quantitated, we observed no statistically significant difference in ductal length, number of terminal end structures or branching between Ccr6WT and Ccr6−/− mice (Additional file 1: Figure S1b-d), and hence the overall effect of CCR6 deletion on normal mammary gland biology appears to be minimal and is unlikely to account for differences in PyMT-driven tumor development between the two genotypes.