Invasive Breast Cancer (IDC/ILC)

Breast cancers that have spread into surrounding breast tissue are known as invasive breast cancer. There are different kinds of invasive breast cancer. Some kinds are more common than others.

Invasive (infiltrating) ductal carcinoma (IDC)

This is the most common type of breast cancer. About 8 of 10 invasive breast cancers are invasive (or infiltrating) ductal carcinomas (IDC).

IDC starts in the cells that line a milk duct in the breast, breaks through the wall of the duct, and grows into the nearby breast tissues. At this point, it may be able to spread (metastasize) to other parts of the body through the lymph system and bloodstream.

Invasive lobular carcinoma (ILC)

Invasive lobular carcinoma (ILC) starts in the milk-producing glands (lobules). Like IDC, it can spread (metastasize) to other parts of the body. About 1  invasive breast cancer in 10  is an ILC. Invasive lobular carcinoma may be harder to detect on physcial exam as well as imaging, like mammograms, than invasive ductal carcinoma. And compared to other kinds of invasive carcinoma, about 1 in 5 women with ILC might have cancer in both breasts.  

Special types of invasive breast cancer

There are some special types of breast cancer that are sub-types of invasive carcinoma. They are much less common than the breast cancers listed named above and each typically make up fewer than 5% of all breast cancers. These are often named after features seen when they are viewed under the microscope, like the ways the cells are arranged.

Some of these may have a better prognosis than standard invasive infiltrating ductal carcinoma. These include:

  • Adenoid cystic (or adenocystic) carcinoma
  • Low-grade adenosquamous carcinoma (this is a type of metaplastic carcinoma)
  • Medullary carcinoma
  • Mucinous (or colloid) carcinoma
  • Papillary carcinoma
  • Tubular carcinoma

Some sub-types have the same or maybe worse prognoses than standard invasive infiltrating ductal carcinoma. These include:

  • Metaplastic carcinoma (most types, including spindle cell and squamous, except low grade adenosquamous carcinoma)
  • Micropapillary carcinoma
  • Mixed carcinoma (has features of both invasive ductal and lobular)

In general, all of these sub-types are still treated like standard invasive infiltrating ductal carcinoma.

Learn about treatments for invasive breast cancer

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

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Last Medical Review: September 25, 2017 Last Revised: September 25, 2017

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