Tumor Pathology

Mercy Breast Center

Important terms to understand about the pathology report:

Non-invasive tumor

Tumors that are confined to the ducts are in-situ or non-invasive. This is called DCIS – ductal carcinoma in situ. These tumor cells cannot spread beyond the breast. This represents Stage 0 disease.

Please note that LCIS or lobular carcinoma in situ is not a cancer.

Invasive tumor

Tumor cells have spread into the breast tissue outside the duct or gland. These tumors have the ability to spread to lymph nodes or elsewhere in the body. The likelihood of spread outside the breast is determined by numerous factors.

Tumor grade

Pathologists divide tumors into three grades based on their appearance under the microscope (how abnormal the cells look). Grade 1 is well differentiated, grade 2 is moderately differentiated and grade 3 is poorly differentiated. This should not be confused with the stage of the disease.

Hormone Receptor Status (ER and PR)

Normal ducts and lobule in the breast have estrogen receptors (ER) and progesterone receptors (PR) expressed on their surface. If tumor cells have these same receptors, they are called ER positive and PR positive, respectively. If they have lost these receptors, they are ER negative and PR negative.

If the tumor is ER or PR positive, the patient is a candidate to receive hormonal agents that block the action of estrogen. The most frequently used hormonal agents are Tamoxifen and Aromatase inhibitors. However, these agents have no role if the tumor is ER and PR negative.


About 20-30% of breast cancers overexpress a growth factor receptor, called HER2/neu - human epidermal growth factor receptor 2.  The pathologists assess all breast tumors for expression of this receptor by two methods - immunohistochemistry (IHC) or fluorescence in situ hybridization (FISH).  A monoclonal antibody that targets the HER2/neu receptor, called Trastuzumab (Herceptin) is now available to treat these tumors.  Your medical oncologist can review the risks and benefits of this drug with you.

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Oncotype Dx

Oncotype Dx is a molecular profiling test of the tumor, usually performed in patients who have Stage I or Stage II hormone receptor positive breast cancers.  It helps determine the magnitude of benefit of giving chemotherapy in addition to hormonal therapy in this group of patients. It also calculates the risk of relapse at 10 years.

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Stage of the tumor

Treatment decisions are made in part according to the stage of the cancer. Some other features of the tumor are taken into consideration – the estrogen-receptor (ER) and progesterone-receptor (PR) status, human epidermal growth factor receptor 2 (HER2/neu) status, and the Oncotype Dx result where applicable. Certain patient-related factors include the age, menopausal status, and the general health of the patient.

The stage defines the extent of a cancer in the body. Staging is usually based on the size of the tumor, whether lymph nodes contain cancer, and whether the cancer has spread from breast to other parts of the body.

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