Finally, it is worth noting that in solid cancers, such as breast cancer, a differential CCR7 expression between different histologic subtypes is determined by tumor microenvironment factors (e.g. hormonal, inflammatory, and growth stimulating) which may disable migration of CCR7-expressing tumor cells towards CCL21 and, consequently, the presence of LN migrations (106). The gene discussed is CCR7; the disease is neoplasm.