P2RY8 and breast cancer: Of the cancer types not depicted in Fig. 6, the breast cancer data set has a commonly co-occurring set of size 4, {CLDN4, INSR, P2RY8, SORL} none of which ranks in the top 20 genes, and the colorectal cancer data set has a different commonly co-occurring set of size 4, {GABRE, GPRR, LGR5, PTPRJ}.