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Malignant breast lumps (breast cancers)

When you read about malignant breast lumps, this means that they are cancerous. It can be hard to understand some of the words you come across when talking or reading about breast cancer. Here, we explain the different breast cancer types and terminologies.

You may come across some of the following terms regarding breast lumps:

Benign breast lumps

Benign tumours are not cancerous. Some may grow or increase in size, but they do not spread outside the breast and are not life threatening.

Find out more about the types of benign breast lumps here.

Malignant breast lumps

Malignant tumours are what are referred to as breast cancer. Cells of malignant tumours have the potential to break off from the main tumour or cancer. From there they can spread to the lymph nodes via the lymphatic ducts, or to more distant organs via the bloodstream.

It is important to understand breast cancer terminology. But this can sometimes be confusing.

There are many kinds of breast cancer. They can be described in terms of their cell type, grade and receptor status.

How far the cells may have spread is referred to as the stage.

These are some of the terms you may come across and what they mean:

1. Cell types of breast cancer

It is important to know that different kinds of breast cancers behave differently and will respond to different treatments than others.

This is important in guiding the treating team in selecting the most appropriate therapies for each individual patient.


A cancer that begins in the lining of the breast ducts (ductal carcinoma) or lobules (lobular carcinoma).


A cancer that starts in glandular tissue (tissue that makes or secretes a substance). The ducts and lobules of the breast are glandular tissue (they make breast milk), so cancers that start in these areas are sometimes called adenocarcinomas.

Carcinoma in situ

This term is used to describe the earliest stage of breast cancer, when it is still only in the layer of cells where it began.

In breast cancer, “in situ” means that the cancer cells are still only in the ducts (ductal carcinoma in situ – DCIS) or in the lobules (lobular carcinoma in situ – LCIS). The cancer cells have not yet invaded the breast tissue. They are sometimes referred to as non-invasive breast cancer.

Invasive (or Infiltrating) carcinomas

An invasive cancer is one that has grown beyond the layer of cells where it started (unlike carcinoma in situ). Most breast cancers are invasive carcinomas – either invasive ductal carcinomas or invasive lobular carcinomas.


These are cancers that start from connective tissue like muscle, fat or blood vessels. Sarcomas of the breast are rare.

Sometimes a breast tumour can be a mix of these types or a mixture of invasive and in-situ cancer.

2. Grades of breast cancer

Grading of a breast cancer is based on the microscopic appearance of the tumour cells and gives an indication of the rate (speed) of growth.

Simplified grades of breast cancer

Grade 1: cells look relatively normal = well defined, slow growing.

Grade 2: characteristics between Grade 1 and 3 = moderately differentiated.

Grade 3: cells lack normal features = poorly differentiated – tend to grow much more quickly.

The grade of a tumour is related to prognosis. The grade 1 or low grade tumour has a better prognosis because it grows more slowly and tends to spread later than higher grade tumours.

Some breast cancer cells have high numbers of receptors for some hormones or growth factors which can influence their growth. The laboratory can do tests for these on the tissue sample from the biopsy.

3. Stages of breast cancer and have excellent information on stages of breast cancer.

The stage of the breast cancer has nothing to do with the type, grade or receptor status of the breast cancer but rather refers to how big the cancer has grown and how far it has spread.

Staging takes into account the following:

  • The size of the tumour
  • where there are any lymph nodes involved
  • and whether it has spread far from its original site or metastasised.

It is an indication of the distance it has spread and not necessarily how that tumour will behave.

Breast cancer cells could spread through either the lymphatics (to the lymph nodes), or via the bloodstream to other parts of the body – such as the bones, lungs and liver.

Simplified stages of breast cancer:

Stage 0: non-invasive (in situ).

Stage 1: invasive but less than 2cm in size and no lymph nodes involved.

Stage 2: invasive with a size of 2-5cm, or smaller but spread to a few lymph nodes in the armpit.

Stage 3: size more than 5cm, or smaller but spread to many lymph nodes which become stuck to one another. Or it has spread to the breast skin, chest wall or internal mammary lymph nodes.

Stage 4: spread to more distant organs.

4. Breast cancer receptors

Some breast cancer cells carry high numbers of receptors to hormones or growth factors which can influence their growth.

The oestrogen and progesterone hormone receptors and the HER2 (human epidermal growth) receptors are common types of receptors in breast cancer cells.

These receptors are detected by the pathology tests which are done on the tumour biopsy.

The reason that this is important is that it can assist in decisions around treatment options.

Hormone receptor-positive

If there are high numbers of oestrogen receptors (ER) or progesterone receptors (PR) reported on the pathology report, the cancer will be called ER or PR positive.

This is important to know in order to plan treatment, as hormone receptor-positive breast cancers will respond well to anti-hormonal treatment (such as Tamoxifen or aromatase inhibitors).

Read more in this article.

HER2 receptor-positive

If there are high numbers of receptors to the human epidermal growth factor receptor 2, the cancer will be called HER2-positive.

HER2-positive tumours tend to be fast-growing. They also respond to the HER2 targeted therapy called Herceptin. has useful information on Her2 receptors.

For more info on your treatment options, read Targeted breast cancer therapies.

More info on breast cancer symptoms, types and treatments’s resource on breast cancer symptoms and types is very useful.

Find out about the various treatments available for breast cancer here.

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