Breast Care A-Z · Condition · IDC

Invasive ductal carcinoma

also: IDC, invasive carcinoma of no special type, NST, infiltrating ductal carcinoma

Invasive ductal carcinoma (IDC) is the most common type of breast cancer — it begins in a milk duct and has grown through the duct wall into the surrounding breast tissue. You have probably been told your biopsy or surgery shows IDC, or are reading to understand what the diagnosis means.

Quick answers

Is invasive ductal carcinoma worse than DCIS?

"Worse" depends on what you mean. IDC has the potential to spread, while DCIS does not — so as a category, invasive disease is more serious. But a small, low-grade, ER-positive IDC with no nodal involvement has an excellent outlook, often better than a large or high-grade DCIS. The diagnosis is the start of the conversation, not the answer.

What is the survival rate?

Outcomes vary widely depending on the size of the cancer, lymph node status, grade, and biological features. For early-stage, well-treated IDC the 5-year and 10-year survival rates are high — well over 90% for many patients. Specific figures for an individual case come from the oncology team after the full picture is established at MDT.

Why is my report saying "invasive carcinoma NST" rather than "invasive ductal carcinoma"?

The two terms mean the same thing. Modern pathology reporting uses no special type (NST) as the standard label, distinguishing this most-common cancer from the "special types" (lobular, tubular, mucinous, etc.). If you see one term in one place and another in a different document, they refer to the same cancer.

PLATE XLI · ONCOLOGY · INVASIVE BREAST CANCER invasive ductal carcinoma IDC · INFILTRATING DUCTAL CARCINOMA · NO SPECIAL TYPE (NST) the most common invasive breast cancer, arising from ductal epithelium with breach of the basement membrane and stromal infiltration 1 FIG 01 — BREAST CROSS-SECTION WITH IDC v skin tethering breach IDC NST LVI i spiculated tumour mass ii basement membrane breach iii desmoplastic stromal reaction iv lymphovascular invasion MOLECULAR SUBTYPES Luminal A ER+/PR+/HER2− Ki67 low Luminal B ER+/HER2+ or Ki67 high HER2-enriched ER−/PR−/HER2+ Triple-negative ER−/PR−/HER2− TRIPLE ASSESSMENT Clinical History + exam Radiological Mammogram + USS Pathological Core biopsy → B5b 2 FIG 02 — ER-POSITIVE vs ER-NEGATIVE IDC ER-positive IDC ER-negative IDC Frequency ~75% of IDC ~25% of IDC Molecular subtype Luminal A/B HER2+ or TNBC Grade Often 1–2 Often 3 Ki67 Low High Prognosis Better Worse Hormone therapy Yes (tamoxifen/AI) No Chemotherapy Selected cases Usually indicated HER2 therapy If HER2+ If HER2+ Age at onset Post-menopausal peak Younger average 5-yr survival ~90%+ ~80% 3 FIG 03 — IDC vs ILC vs DCIS Feature IDC (NST) ILC Frequency ~80% invasive ~15% invasive Pattern Irregular mass Diffuse infiltration Mammogram Spiculated mass Often occult Bilaterality <5% 10–15% ER status ~75% ER+ >90% ER+ HER2 Variable Rare E-cadherin Positive Lost (negative) Metastatic sites Lung, liver, bone Peritoneum, GI, meninges Prognosis Grade-dependent Generally similar 4 FIG 04 — CLINICAL PATHWAY Presentation (lump/screen) → Triple assessment clinical + imaging + biopsy → Staging CT + bone scan ↓ MDT decision multidisciplinary ← Surgery WLE/mastectomy + SLNB ← Adjuvant therapy chemo/hormone/RT 5 FIG 05 — IDC SUBTYPES OVERVIEW IDC Grade 1 Well differentiated Low mitoses · ER+ FAVOURABLE IDC Grade 2 Moderately differentiated Intermediate features INTERMEDIATE IDC Grade 3 Poorly differentiated High mitoses · aggressive HIGHER RISK IDC with DCIS Mixed invasive + in situ component COMMON PATTERN Luminal A subtype ER+/PR+/HER2− Ki67 low · best outcomes BEST PROGNOSIS Triple-negative IDC ER−/PR−/HER2− Chemo backbone CHALLENGING 6 FIG 06 — KEY STATISTICS ~80% of all invasive breast cancers [1] ~99% 5-yr survival, Stage I [2] 61 yrs median age at diagnosis [3] ~75% are ER-positive [4] 7 FIG 07 — REFERENCES 1. Makki J. Diversity of breast carcinoma. Clin Med Insights Pathol 2015 2. Cancer Research UK. Survival statistics 2024 3. ONS. Cancer registration statistics England 2022 4. NICE NG101. Early and locally advanced breast cancer 2023 5. WHO Classification of Tumours: Breast 5th ed. IARC 2022 Clinically authored by Dr Fiona Tsang-Wright , FRCS (Gen Surg) GMC 4549831 · ORCID 0000-0003-4801-026X
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Definition
Invasive ductal carcinoma is the most common type of invasive breast cancer, accounting for around 80% of cases — a cancer that began in the milk ducts and has grown through the duct wall into the surrounding breast tissue.

Common questions The questions patients ask first

Is invasive ductal carcinoma worse than DCIS?
'Worse' depends on what you mean. IDC has the potential to spread, while DCIS does not — so as a category, invasive disease is more serious. But a small, low-grade, ER-positive IDC with no nodal involvement has an excellent outlook, often better than a large or high-grade DCIS5. The diagnosis is the start of the conversation, not the answer.
What is the survival rate?
Outcomes vary widely depending on the size of the cancer, lymph node status, grade, and biological features. For early-stage, well-treated IDC the 5-year and 10-year survival rates are high — well over 90% for many patients5. Specific figures for an individual case come from the oncology team after the full picture is established at MDT.
Why is my report saying 'invasive carcinoma NST' rather than 'invasive ductal carcinoma'?
The two terms mean the same thing1. Modern pathology reporting uses no special type (NST) as the standard label, distinguishing this most-common cancer from the 'special types' (lobular, tubular, mucinous, etc.). If you see one term in one place and another in a different document, they refer to the same cancer.
Will I need chemotherapy?
Not necessarily2. Chemotherapy is recommended for cancers where the absolute benefit is clinically meaningful6 — usually larger cancers, higher-grade cancers, those with significant lymph node involvement, or those with biological features (HER2 positive4, ER negative, high genomic test score7) that predict benefit. Many patients with smaller, ER-positive cancers do not need chemotherapy. The decision is made at MDT and discussed with you in clinic.

Invasive ductal carcinoma is the most common type of invasive breast cancer, accounting for around 70–80% of cases1 — a cancer that began in the milk ducts and has grown through the duct wall into the surrounding breast tissue.

IDC is the breast cancer most patients are referring to when they say “breast cancer”. The treatment is determined by the cancer’s biology — its size, grade, hormone-receptor status, and HER2 status — rather than by the IDC label itself. The newer term in pathology is invasive carcinoma of no special type (NST), which means the same thing.

Orientation Why you might be reading about this

You have probably been told that your biopsy or surgery shows invasive ductal carcinoma, or you are reading to understand what that diagnosis means. The label can sound serious in isolation; what it tells you is the cancer’s type, but not its severity — that depends on the additional features described in the histology report. This page explains what IDC is and how it sits within the broader cancer picture.

Related terms: DCIS · Invasive lobular carcinoma · Mastectomy · Lumpectomy · Oestrogen receptor · HER2

Definition What “invasive ductal carcinoma” means in practice

The breast is built around a system of milk ducts — small tubes that lead from the milk-producing lobules to the nipple. Ductal carcinoma in situ (DCIS) is cancer that has formed inside the duct lining but has not yet broken through the duct wall. Invasive ductal carcinoma is cancer that has done so — the cells have crossed the duct wall and are growing in the surrounding breast tissue.

Once a cancer is invasive, it has the potential — though not the certainty — to spread further: to nearby lymph nodes and, in some cases, beyond. Most modern cancer treatment is built around this distinction: in-situ disease (DCIS) is treated with surgery and sometimes radiotherapy alone, while invasive disease is treated with surgery, often radiotherapy, and (depending on the cancer’s biology) systemic treatments such as chemotherapy, hormone therapy, or targeted therapy.

The newer pathology term invasive carcinoma of no special type (NST) has largely replaced invasive ductal carcinoma in formal reports1. The two mean the same thing — they refer to the most common form of invasive breast cancer, distinguished from “special type” invasive cancers (invasive lobular carcinoma, tubular, mucinous, medullary, and others) that have specific microscopic features.

How it differs How IDC differs from in-situ disease

The key practical differences:

Feature DCIS Invasive ductal carcinoma
Cells confined to duct? Yes No (have grown through duct wall)
Can it spread to lymph nodes? No Yes (in some cases)
Sentinel lymph node biopsy? Sometimes (with mastectomy — because a small proportion of DCIS is upgraded to invasive cancer on final pathology, and SLNB cannot be done retrospectively once the breast is removed) Almost always
Adjuvant systemic treatment? Hormone therapy in selected cases Often (decided by biology)
Radiotherapy after lumpectomy? Usually Almost always

A patient with a small, low-grade IDC and no lymph node involvement may have an excellent outlook with a treatment that is, in practical terms, similar to DCIS treatment plus a sentinel biopsy. The “invasive” label by itself does not predict outcome — the additional histology features do.

Pathology What the histology report tells the team

After a biopsy or surgery, the pathologist reports on:

  • Size of the invasive cancer.
  • Grade — a measure of how aggressive the cells look, scored 1–3. See grade and stage.
  • Hormone-receptor status — whether the cancer is oestrogen receptor (ER) positive and progesterone-receptor (PR) positive. ER-positive cancers respond to hormone therapy.
  • HER2 status — positive or negative; HER2-positive cancers respond to targeted antibody therapies.
  • Lymph node status — once the sentinel or axillary specimen is examined, the report includes how many of the removed nodes contain cancer.
  • Margins — whether the cancer has been removed with a clear rim of healthy tissue.

Together, these features determine the multidisciplinary team’s recommended treatment plan — surgery type, radiotherapy, hormone therapy, chemotherapy, targeted therapy.

Treatment Treatment overview

Treatment for IDC follows the same principles as for any invasive breast cancer:

  • Surgery — lumpectomy plus radiotherapy, or mastectomy (with or without reconstruction), depending on the cancer’s size, position, and the patient’s preference2. Sentinel lymph node biopsy is part of either operation.
  • Radiotherapy — recommended after lumpectomy in most cases; in selected older patients with small, low-risk, ER-positive cancers, the MDT may discuss omitting radiotherapy. Sometimes recommended after mastectomy if there is significant nodal involvement or other risk factors2.
  • Hormone therapy (tamoxifen, aromatase inhibitors) — for ER-positive cancers, typically for 5–10 years3.
  • Targeted therapy — for HER2-positive cancers (trastuzumab, pertuzumab), typically for 12 months4.
  • Chemotherapy — recommended for higher-risk cancers based on size, grade, lymph node status6, and modern genomic tests (Oncotype DX, MammaPrint)7.

Most patients with IDC do not need every treatment; the plan is tailored to the individual cancer.

At consultation What to discuss with your surgeon

Once a diagnosis of IDC is established, the conversation usually covers:

  • The full histology — size, grade, ER/PR/HER2 status, and what each means.
  • Surgical options — lumpectomy versus mastectomy, with or without reconstruction.
  • The MDT plan for adjuvant treatment, once the operation specimen has been reviewed.
  • The likely overall outlook — given the specific features of your cancer, what to expect over the next year and the next decade.

Once the histology is complete, a second-opinion consultation is a routine way to review the proposed plan before you decide.

Resources Further reading

Sources & guidance

Every figure on this page is anchored to a published source. Tap a number in the text or below to jump to the reference.

  1. reference text WHO Classification of Tumours Editorial Board. Breast Tumours. WHO Classification of Tumours, 5th edition, vol. 2. Lyon: International Agency for Research on Cancer. 2019 ;Invasive carcinoma of no special type https://tumourclassification.iarc.who.int/ Cited for: Definition of invasive carcinoma of no special type (NST), formerly invasive ductal carcinoma; relative frequency among invasive breast cancers (~70–80%).
  2. guideline National Institute for Health and Care Excellence. Early and locally advanced breast cancer: diagnosis and management (NG101). London: NICE. 2018 ;Last updated 2024 https://www.nice.org.uk/guidance/ng101 Cited for: UK pathway for surgery, radiotherapy and adjuvant systemic therapy decisions in invasive breast cancer.
  3. meta analysis Early Breast Cancer Trialists' Collaborative Group (EBCTCG). Relevance of breast cancer hormone receptors and other factors to the efficacy of adjuvant tamoxifen: patient-level meta-analysis of randomised trials. The Lancet. 2011 ;378(9793):771-784 doi:10.1016/S0140-6736(11)60993-8 Cited for: Magnitude and durability of tamoxifen benefit in ER-positive breast cancer; ~50% reduction in recurrence over 5 years.
  4. review Loibl S, Gianni L. HER2-positive breast cancer. The Lancet. 2017 ;389(10087):2415-2429 doi:10.1016/S0140-6736(16)32417-5 Cited for: HER2 overexpression frequency (~15-20%); adjuvant trastuzumab benefit and 12-month duration standard.
  5. cohort Allemani C, Matsuda T, Di Carlo V, et al. Global surveillance of trends in cancer survival 2000-14 (CONCORD-3): analysis of individual records for 37 513 025 patients diagnosed with one of 18 cancers from 322 population-based registries in 71 countries. Lancet. 2018 ;391(10125):1023-1075 doi:10.1016/S0140-6736(17)33326-3 Cited for: International population-based survival benchmarks for breast cancer; >90% 5-year survival for early-stage disease in high-income settings.
  6. meta analysis Early Breast Cancer Trialists' Collaborative Group (EBCTCG). Comparisons between different polychemotherapy regimens for early breast cancer: meta-analyses of long-term outcome among 100,000 women in 123 randomised trials. Lancet. 2012 ;379(9814):432-444 doi:10.1016/S0140-6736(11)61625-5 Cited for: EBCTCG polychemotherapy meta-analysis: magnitude of adjuvant chemotherapy benefit in early breast cancer.
  7. rct Sparano JA, Gray RJ, Makower DF, et al. Adjuvant chemotherapy guided by a 21-gene expression assay in breast cancer. New England Journal of Medicine. 2018 ;379(2):111-121 doi:10.1056/NEJMoa1804710 Cited for: TAILORx: 21-gene Oncotype DX recurrence-score-guided chemotherapy decisions in ER-positive HER2-negative early breast cancer.