In human (ER−) HER2+ breast cancer, the PVT1 intron 1, which is close to the PVT1 promoter, is abnormally prone to cleavage, which might result in the fusion of PVT1 with another gene on the same chromosome leading to an abnormal transcription process not regulated by the PVT1 promoter. This evidence concerns the gene PVT1 and breast cancer.