How Common Is Invasive Ductal Carcinoma Compared With DCIS?

Invasive ductal carcinoma (IDC)—increasingly referred to by pathologists as invasive carcinoma of no special type—is the most common type of breast cancer. When looking at broad United States population estimates for all new breast cancer diagnoses, roughly 20% to 25% are ductal carcinoma in situ (DCIS), while the remaining 75% to 80% are invasive breast cancers ^[1][2].

Of those invasive cancers, approximately 70% to 80% are invasive ductal carcinoma ^[3].

A critical fact to understand right away: “invasive” does not mean your cancer is metastatic or Stage IV. “Invasive” simply means the cancer cells have stepped outside the exact location where they formed, but many invasive cancers are caught early and remain localized to the breast or nearby lymph nodes.

Invasive Breast Cancer vs. DCIS

Breast cancers are broadly categorized based on whether the abnormal cells have broken through the natural barriers of the breast’s milk ducts or milk-producing glands (lobules).

• Ductal Carcinoma In Situ (DCIS): DCIS is defined as non-invasive (or pre-invasive) because the abnormal cells are confined entirely within the milk ducts ^[4]. They have not broken through the duct wall (the basement membrane) into the surrounding breast tissue ^[5]. Roughly 50,000 cases of DCIS are diagnosed each year in the United States ^[6], accounting for about 1 in 5 (20–25%) of all new breast cancer diagnoses ^[1][2].
• Invasive Breast Cancer: If the cancer cells break through the basement membrane of a duct or lobule into the surrounding breast tissue, the diagnosis becomes invasive ^[4][5]. The vast majority of newly diagnosed breast cancers (close to 80%) fall into this category ^[7].

If your biopsy shows both DCIS and an invasive cancer, your care team will primarily base your treatment plan and overall stage on the invasive component.

Breakdown of Invasive Breast Cancers

When a tumor is invasive, pathologists further classify it by its histology, which means how the cells look under a microscope. While percentages can vary slightly depending on the specific registry and year, general estimates show:

• Invasive Ductal Carcinoma (IDC): This is the most common subtype, representing about 70% to 80% of all invasive breast cancers ^[3].
• Invasive Lobular Carcinoma (ILC): The second most common type, making up approximately 10% to 15% of invasive breast cancers ^[8][9].
• Mixed and Rare Subtypes: A small percentage of cancers have a mix of ductal and lobular features, or belong to rarer subtypes like tubular or mucinous carcinomas ^[10][11].

What Do These Statistics Mean for My Outlook?

While it is natural to wonder what incidence statistics mean for your future, how common a cancer is does not determine its severity or your prognosis. Knowing that IDC is the most common type of breast cancer simply means that oncologists have extensive experience treating it, and there is a wealth of research guiding standard-of-care treatments.

Instead of population statistics, your individual outlook is determined by a formal assessment called prognostic staging ^[12][13]. This formal stage combines:

• Anatomic Stage: The physical size of the tumor and whether cancer cells have spread to nearby lymph nodes or other parts of the body ^[12].
• Tumor Biology (Biomarkers): Whether your cancer cells are fueled by hormones (estrogen and progesterone receptors, or ER/PR) or overexpress a growth-promoting protein called HER2 ^[14].
• Tumor Grade: How abnormal the cancer cells look compared to healthy cells, which helps estimate how aggressively the cancer may behave ^[15].

Beyond formal staging, other personal factors guide your specific treatment decisions:

• Genomic Assays: For certain early-stage, hormone-receptor-positive cancers, specialized tests (like Oncotype DX or MammaPrint) analyze the genes within the tumor. These help predict recurrence risk and whether chemotherapy will be beneficial, though they are not used for every patient ^[14].
• Your Age and Overall Health: Your body’s ability to tolerate different treatments and any other health conditions you may have play a major role in your care plan ^[16].

Because breast cancer is biologically complex, two people with IDC can have completely different treatment paths and outlooks ^[17][18]. Discussing your specific pathology report with your care team will give you a much more accurate picture of your outlook than general population statistics ^[14].