all of which are described at www.genenames.org. Gene symbols are italicized whereas symbols for gene products are not italicized.

248 Word count, text (from the beginning of Introduction to the end of Discussion): 4,467 Reference count: 48 Table count: 3 Figure count: 3 Supplementary online material: 12 figures and 8 tables Disclosure of Potential Conflicts of Interest: M.C.L., J.B., S.O., and J.A.N. are listed as co-inventors on a provisional application for a patent titled "System for and Method of Discovering Spatially-Derived Signatures of Tumor-Immune Cell Interactions through Tumor-Immune Partitioning and Clustering" regarding novel methods for characterizing immune cell distributions in solid tumors that has been filed through Partners Healthcare. J.L.G. is a consultant for GlaxoSmithKline, Codagenix, Array BioPharma, and Verseau Therapeutics; and receives research support from GlaxoSmithKline, Eli Lilly and Array BioPharma for the study of the breast tumor microenvironment. A.T.