Prostate cancer is generally multifocal and consists of a dominant focus—measured by tumour volume and deemed the index lesion—and one or more separate, secondary tumour foci of smaller volume. Much laboratory and clinical evidence has shown that we need to rethink how we regard low-grade and low-volume prostate lesions. In this Personal View, we discuss why small, low-grade Gleason pattern prostate lesions, which are currently designated as prostate cancer, could be regarded as non-malignant. These lesions either do not meet the criteria of the hallmarks of cancer or robust evidence that they do so is absent, by contrast with large lesions with a high Gleason grade, which seem to cause most metastatic disease.