PPM1A and breast cancer: To examine whether PPM1A deletion was more often seen in a particular breast cancer subtype, we compared the somatic alteration of PPM1A across different breast cancer subsets defined by Pam50 gene signatures.32 PPM1A deletion was seen most commonly in basal breast cancers, at a rate of approximately 60%, while a rate of only 10–20% was observed in other breast cancer subtypes.