In colon cancer, elevated GM-CSF serum levels due to factor secreting tumors coincide with disseminated tumors and eosinophilia 20, and Tomita et al. 21 describe a GM-CSF regulated increase in tumor cell invasion via the stimulation of matrix metallo-proteinase 2 (MMP-2) and MMP-14 in HNSCC. Here, MMP2 is linked to Increased total eosinophil count.