# Intraductal carcinoma of the prostate (IDC-P)

Source: https://onco.cc/terms/intraductal-carcinoma-prostate/  
OnCo record `intraductal-carcinoma-prostate` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Cancer cells filling prostate ducts and acini that still have their own outer basal cell layer. It is almost always found beside an invasive cancer, it marks a worse outlook, and on its own it is one of the reasons the NHS and the NCCN offer inherited-cancer gene testing.

## Summary

The WHO fifth edition defines intraductal carcinoma of the prostate as a neoplastic epithelial proliferation involving pre-existing, generally expanded duct and acinar structures, with architectural and cytological atypia beyond what is acceptable for high-grade prostatic intraepithelial neoplasia: lumen-spanning solid or cribriform patterns, or loose cribriform and micropapillary patterns with enlarged nuclei. The basal cell layer is retained, which is what separates it from invasive cribriform cancer and which usually needs an immunohistochemical stain for p63 and high-molecular-weight cytokeratin to demonstrate. The fifth edition also introduces atypical intraductal proliferation for lesions with more atypia than high-grade PIN but less than IDC-P, and moves what used to be called cribriform high-grade PIN into that category.

The Royal College of Pathologists made reporting the presence of intraductal carcinoma a core item of the UK dataset in its 2024 revision, alongside invasive cribriform carcinoma and the percentage of Gleason pattern 4. Two things follow from finding it. It is associated with high-grade disease and a poor prognosis, so it argues against active surveillance. And both the NCCN and the Philadelphia Prostate Cancer Consensus Conference recommend germline genetic testing for anyone whose prostate cancer shows intraductal or cribriform morphology, although a large case-control study found no association between germline BRCA2 mutations and either pattern while still finding one with somatic biallelic loss in the tumour.

Whether foci of IDC-P should be counted when the Gleason grade is assigned is unresolved and reported practice varies. The 2014 ISUP consensus said not to grade IDC-P without invasive carcinoma and the 2016 WHO edition went further, saying it should not be factored into grading at all; the two main urological pathology societies now diverge on the point and the fifth edition deliberately endorses neither, asking instead that pathologists state which convention their report follows. A study of biopsies from 1,031 men found that including IDC-P and invasive cribriform carcinoma in the grade group improved prediction of metastasis-free and disease-specific survival, though not of biochemical recurrence.

## Fields

- Kind: Term
- Last checked: 2026-09-25
- Also known as: IDC-P; IDC; intraductal carcinoma; intraductal; intraductal prostate; atypical intraductal proliferation; AIP

## Sources

- Royal College of Pathologists G084: dataset for histopathology reports for prostatic carcinoma, version 4, October 2024: https://www.rcpath.org/static/8cc88604-2c8d-4df4-a99542df41c102af/G084-dataset-for-histopathology-reports-for-prostatic-carcinoma.pdf
- Kench et al., Histopathology 2022: WHO Classification of Tumours fifth edition, evolving issues in the classification, diagnosis and prognostication of prostate cancer: https://doi.org/10.1111/his.14711
- WHO Classification of Tumours, 5th edition: tumours of the prostate (IARC, 2022): https://tumourclassification.iarc.who.int/chapters/36

## Connected records

- terms: [Acinar adenocarcinoma of the prostate](https://onco.cc/terms/prostate-acinar-adenocarcinoma/), [Carcinoma in situ (CIS)](https://onco.cc/terms/carcinoma-in-situ/), [Cribriform growth pattern in prostate cancer](https://onco.cc/terms/cribriform-prostate-cancer/), [Gleason score / Grade Group](https://onco.cc/terms/gleason-grade-group/), [High-grade prostatic intraepithelial neoplasia (HGPIN)](https://onco.cc/terms/high-grade-pin/), [Percentage of Gleason pattern 4](https://onco.cc/terms/percentage-gleason-pattern-4/), [Whole-mount pathology](https://onco.cc/terms/whole-mount-pathology/)
- technologies: [Germline (hereditary) testing](https://onco.cc/technologies/germline-testing/), [Histopathology & immunohistochemistry](https://onco.cc/technologies/histopathology-ihc/)
- cancers: [Ductal adenocarcinoma of the prostate](https://onco.cc/cancers/prostate-ductal-adenocarcinoma/), [Localised prostate cancer, high and very high risk](https://onco.cc/cancers/prostate-high-risk/), [Localised prostate cancer, intermediate risk](https://onco.cc/cancers/prostate-intermediate-risk/), [Prostate cancer](https://onco.cc/cancers/prostate/)
- fronts: [Diagnostics & Biomarkers](https://onco.cc/fronts/diagnostics/)
- key papers: [Germline BRCA2 mutations drive prostate cancers with distinct evolutionary trajectories](https://onco.cc/key-papers/paper-taylor-germline-brca2-evolutionary-trajectories-nat-commun-2017/), [In vivo amplification of the androgen receptor gene and progression of human prostate cancer](https://onco.cc/key-papers/paper-visakorpi-ar-amplification-recurrent-prostate-nat-genet-1995/), [Intraductal and ductal histology and lymphovascular invasion are associated with germline DNA-repair gene mutations in prostate cancer](https://onco.cc/key-papers/paper-isaacsson-velho-intraductal-germline-dna-repair-prostate-2018/)

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