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Invasive and Infiltrating Cancer

The term "invasive" or "infiltrating" cancer means that cancer cells have spread beyond the lining of the milk duct. It is most frequently discovered as a lump which can be felt on physical exam or seen on mammography and/or ultrasound.

Other signs of breast cancer include:

  • Skin changes such as thickening or retraction
  • Nipple retraction
  • A localized area of nodularity on physical exam
  • Spontaneous nipple discharge originating from a single milk duct
  • Axillary (underarm) lymph node enlargement

The majority of invasive breast cancers are classified as ductal, which means the cancer started within the milk duct. A small number of cancers are tubular, papillary, medullary or mucinous. These types of cancer typically provide a better prognosis for the patient.

Approximately 20% of breast cancers are called lobular, meaning the origin of the cancer is the portion of the milk gland called a lobule.

A growth which is not invasive and not considered cancerous is lobular carcinoma in situ (LCIS). However, women who are diagnosed with LCIS have about a one percent year risk of developing breast cancer. An invasive cancer can occur in either breast, not necessarily where the LCIS was found. LCIS is not a cancer, but rather a marker of increased risk of development of cancer in either breast.

There are other less common forms of breast cancer. Inflammatory breast cancer causes redness and swelling which could be confused with an inflammatory reaction to infection or injury. This type of cancer grows quickly and treatment for this cancer needs to begin as soon as possible. Another type is Paget's Disease which presents as scaling on the nipple. This is most often associated with an underlying infiltrating ductal carcinoma.

Successful treatment of breast cancer depends on several factors, a discussion of which follows.

Tumor Grade

Tissue removed at biopsy is examined under a microscope by a pathologist. The grade of tumor is made by determining how the cells look. A tumor with cells that more closely resemble normal cells will be given a low grade. A tumor with a high grade is a more aggressive cancer. The pathologist also looks at how the cells are dividing. A slowly growing tumor will have few cells dividing, whereas a faster growing tumor will have cells that divide rapidly. Four categories of grade are currently recognized:

  • Grade 1 - Well differentiated (low grade)
  • Grade 2 - Moderately differentiated (intermediate grade)
  • Grade 3 - Poorly differentiated (high grade)
  • Grade 4 - Undifferentiated (high grade)

Tumor Stage

Staging cannot be determined at the time of the initial biopsy. In staging a breast cancer, several factors are considered. The size of the tumor, the presence of tumor cells in lymph nodes and the presence of metastases to other body parts. Tumor size and lymph node involvement can be ascertained by the pathologist when the cancer is removed at surgery. Metastasis to other parts of the body is determined by x-rays, CAT scans and blood work. There are five stages of breast cancer:

  • Stage 0
  • Stage 1
  • Stage 2
  • Stage 3
  • Stage 4
  • Stage 5

Please visit the American Cancer Society and the National Cancer Insitute for more information on staging.

Hormone (estrogen and progesterone) receptor status

Some breast cancer cells contain hormone receptors on the surface. Receptors are structures that capture hormone molecules from the blood stream, attach them to the cells and allow them to stimulate tumor growth. A cancer that is stimulated to grow by the hormone estrogen is ER-positive. Likewise, a cancer that is stimulated to grow with progesterone is PR-positive. These cancers can be treated with medications that reduce the amount of estrogen in the body or by keeping the hormone from reaching the receptor. Some breast cancer cells are ER-PR negative, meaning they are not stimulated to grow with estrogen or progesterone.

Please visit for more information on hormone receptors.

HER2/neu status

Human Epidermal growth factor Receptor 2 (HER2 or HER2/neu) is a gene which helps normal cells grow. About 25% of breast cancer tumors are HER2/neu positive. This means the cancer cells have an abnormally high number of HER2 genes in each cell and as a result, too much HER2 protein appears on the surface of the cancer cells. This excess amount of protein causes cancer cells to grow and divide more quickly. For this reason, HER2 positive cancer is considered more aggressive and requires prompt treatment.

A patient whose tumor is HER2/neu positive can benefit from treatment with a special group of medications such Herceptin and Tykerb. These medications work by attaching to cancer cells and telling the body's defense system to target the HER2+ cancer cells or by shutting down the growth pathway of cancer cells.

Please visit for more information on HER2/neu treatment.

Oncotype DX

Oncotype DX is a relatively new test used to determine which chemotherapy regimen is best for a particular patient. It is performed only on estrogen receptor-positive tumors which have not spread to the lymph nodes. This test can only be performed after surgical pathology evaluation is complete. Your surgeon will order this test if it is indicated.

Please visit for information on this test.


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