ERBB2 and prostate cancer: Cholesterol sulfate, a structural componentof cellular membranes, has been previously identified in DESI MS experimentsas a potential biomarker of prostate cancer. Here it is a strong contributor to the “yellow” cornerof low dimensional space where pixels from the ErbB2 tumor are positioned.This appears to be a strong marker for ErbB2 over MYC tumors and NMGand it is localized across the whole tumor.