As the impact of stromal and/or immune cell SK4 channels on tumour development might differ between highly malignantly and slowly progressing tumours, we analysed whether SK4 activity affects the survival rates in an alternative mouse model of spontaneously occurring tumours, that is the MMTV‐cNeutg/+ breast cancer model (Guy et al., 1992b). The gene discussed is KCNN4; the disease is breast cancer.