ER-positive patients treated with tamoxifen (n = 304):– Nuclear SK1 expression is associated with shorter time to recurrence on tamoxifen and shorter disease-specific survival– High levels of cytoplasmic SK1 and cytoplasmic ERK1/2 are associated with shorter time to recurrence on tamoxifen– High membrane S1PR1 expression is associated with shorter time to recurrence– High cytoplasmic S1PR3 expression is associated with shorter disease-specific survival– Membrane and cytoplasmic S1PR3 expression correlated with PR status and nuclear S1PR3 correlated with tumor size. The gene discussed is MAPK3; the disease is neoplasm.