Consistent with the known role of myeloid cells in promoting 4T1 tumor metastasis [26, 27, 29], we observed isolated regions of metastatic mammary carcinoma cells in the lungs of SHIP−/− mice (Supplemental Fig. 4C), while there were no obvious microscopic pulmonary metastases in WT mice 15 days after 4T1 tumor implantation. This evidence concerns the gene INPP5D and neoplasm.