In node-negative, SHR-positive undifferentiated (G3) tumours, patients with a PIK3CA-mutation (n = 14) had a worse 5 year-RFI (70.5%) than those with wildtype PIK3CA (5 year RFI 96.4%, HR 11.92; 95% CI 1.724–82.461, p = 0.012). Here, PIK3CA is linked to neoplasm.