Khani F, et al. - Because intraductal carcinoma of the prostate (IDC-P) most often seems to be related to high-grade invasive prostate carcinoma (PCa), where it is believed to be a retrograde spread, however, IDC-P rarely occurs as an isolated finding in radical prostatectomy or concurrent low-grade (Grade Group 1) invasive carcinoma, investigators hypothesized that in these unusual cases isolated IDC-P (iIDC-P) may represent a distinct in situ lesion and molecularly profiled 15 cases. Findings revealed that iIDC-P is enriched with potentially targetable oncogenic driver mutations in MAPK/PI3K genes despite a copy number alteration profile similar to conventional PCa. Based on the status of PTEN and ERG, iIDC-P is unlikely to be a precursor to the associated low-grade invasive PCa, but is an unclear clinical significance molecularly unique in situ tumor.