by Jason Wasserman MD PhD FRCPC
November 17, 2023
Invasive apocrine carcinoma is a rare type of breast cancer. Although it starts from epithelial cells normally found inside the ducts and glands in the breast, the tumour is made up of large pink cells that resemble the cells normally found in apocrine-type sweat glands in the skin.
This article was written by doctors to help you read and understand your pathology report for invasive apocrine carcinoma of the breast. The sections below describe the results found in most pathology reports, however, all reports are different and results may vary. Contact us if you have any questions about this article or your pathology report. Read this article for a more general introduction to the parts of a typical pathology report.
Invasive apocrine carcinoma is a rare type of cancer, representing approximately 1% of all breast cancers.
This type of cancer often presents as a noticeable lump in the breast.
Most invasive apocrine carcinomas are sporadic which means the tumour develops without any known genetic or environmental cause.
The diagnosis of invasive apocrine carcinoma is usually made after a small sample of the tumour is removed in a procedure called a biopsy. The tissue is then sent to a pathologist for examination under a microscope.
When examined under a microscope, invasive apocrine carcinoma is made up of large pink cells that look very similar to the cells found in a type of sweat gland called an apocrine gland. The cells appear pink because the cytoplasm of the cell (body of the cell) is full of a protein that sticks to eosin, a pink-coloured dye found in the hematoxylin and eosin (H&E) stain. The nucleus of the cell (the part of the cell that holds the genetic material) tends to be large and round and clumps of genetic material called nucleoli are often seen. The tumour cells often produce a protein called androgen receptor (AR) which pathologists can see by performing a test called immunohistochemistry.
The Nottingham histologic grading system is used to divide invasive apocrine carcinoma into three levels or grades numbered 1, 2, and 3. The grade is important because grade 2 and grade 3 tumours tend to grow more quickly and are more likely to spread to other parts of the body such as lymph nodes.
The Nottingham grade can only be determined after the tumour is examined under the microscope. When examining the tumour, pathologists look for the following three microscopic features:
The score from each category is added to determine the overall grade as follows:
The size of a breast tumour is important because it is used to determine the pathologic tumour stage (pT) and because larger tumours are more likely to metastasize (spread) to lymph nodes and other parts of the body. The tumour size can only be determined after the entire tumour has been removed. For this reason, it will not be included in your pathology report after a biopsy.
Prognostic markers are proteins or other biological elements that can be measured to help predict how a disease such as cancer will behave over time and how it will respond to treatment. The most commonly tested prognostic markers in the breast are the hormone receptors estrogen receptor (ER) and progesterone receptor (PR) and the growth factor HER2.
ER and PR are hormone receptors that allow cells to respond to the actions of the sex hormones estrogen and progesterone. ER and PR are made by normal breast cells and by some breast cancers.
Your pathologist will perform a test called immunohistochemistry to see if the cells in the tumour are making ER and PR. This test is often performed on the biopsy sample. However, in some situations, it may only be performed after the entire tumour is removed.
Pathologists determine the ER and PR scores by measuring the percentage of tumour cells that have protein in a part of the cell called the nucleus and the intensity of the stain. Most reports give a range for the percentage of cells that show nuclear positivity while the intensity is described as weak, moderate, or high.
HER2 is a protein that is made by normal, healthy cells throughout the body. The tumour cells in some types of cancer make extra HER2 and this allows the cells in the tumour to grow faster than normal cells.
Two tests are commonly performed to measure the amount of HER2 in tumour cells. The first test is called immunohistochemistry and it allows your pathologist to see the HER2 protein on the surface of the cell. This test is given a score of 0 through 3.
HER2 immunohistochemistry score:
The second test that is used to measure HER2 is called fluorescence in situ hybridization (FISH). This test is usually only performed after a score of 2 on the immunohistochemistry test. Instead of looking for HER2 on the outside of the cell, FISH uses probes that stick to the HER2 gene inside the nucleus of the cell. Normal cells have 2 copies of the HER2 gene in the nucleus of the cell. The purpose of the HER FISH test is to identify tumour cells that have more copies of the HER2 gene which allows them to make more copies of the HER2 protein.
HER2 FISH score:
Invasive apocrine carcinoma starts inside the breast but the tumour may spread into the overlying skin or the muscles of the chest wall. The term tumour extension is used when tumour cells are found in either the skin or the muscles below the breast. Tumour extension is important because it is associated with a higher risk that the tumour will grow back after treatment (local recurrence) or that cancer cells will travel to a distant body site such as the lung. Tumour extension is also used to determine the pathologic tumour stage (pT).
Lymphovascular invasion means that cancer cells were seen inside a blood vessel or lymphatic vessel. Blood vessels are long thin tubes that carry blood around the body. Lymphatic vessels are similar to small blood vessels except that they carry a fluid called lymph instead of blood. The lymphatic vessels connect with small immune organs called lymph nodes that are found throughout the body. Lymphovascular invasion is important because cancer cells can use blood vessels or lymphatic vessels to spread to other parts of the body such as lymph nodes or the lungs.
Lymph nodes are small immune organs found throughout the body. Cancer cells can spread from a tumour to lymph nodes through small vessels called lymphatics. For this reason, lymph nodes are commonly removed and examined under a microscope to look for cancer cells. The movement of cancer cells from the tumour to another part of the body such as a lymph node is called a metastasis.
Cancer cells typically spread first to lymph nodes close to the tumour although lymph nodes far away from the tumour can also be involved. For this reason, the first lymph nodes removed are usually close to the tumour. Lymph nodes further away from the tumour are only typically removed if they are enlarged and there is a high clinical suspicion that there may be cancer cells in the lymph node.
If any lymph nodes were removed from your body, they will be examined under the microscope by a pathologist and the results of this examination will be described in your report. Most reports will include the total number of lymph nodes examined, where in the body the lymph nodes were found, and the number (if any) that contain cancer cells. If cancer cells were seen in a lymph node, the size of the largest group of cancer cells (often described as “focus” or “deposit”) will also be included.
The examination of lymph nodes is important for two reasons. First, this information is used to determine the pathologic nodal stage (pN). Second, finding cancer cells in a lymph node increases the risk that cancer cells will be found in other parts of the body in the future. As a result, your doctor will use this information when deciding if additional treatment such as chemotherapy, radiation therapy, or immunotherapy is required.
Pathologists often use the term “positive” to describe a lymph node that contains cancer cells. For example, a lymph node that contains cancer cells may be called “positive for malignancy” or “positive for metastatic carcinoma”.
Pathologists often use the term “negative” to describe a lymph node that does not contain any cancer cells. For example, a lymph node that does not contain cancer cells may be called “negative for malignancy” or “negative for metastatic carcinoma”.
Pathologists use the term ‘isolated tumour cells’ to describe a group of tumour cells that measures 0.2 mm or less and is found in a lymph node. Lymph nodes with only isolated tumour cells (ITCs) are not counted as being ‘positive’ for the pathologic nodal stage (pN).
A ‘micrometastasis’ is a group of tumour cells that measures from 0.2 mm to 2 mm and is found in a lymph node. If only micrometastases are found in all the lymph nodes examined, the pathologic nodal stage is pN1mi.
A sentinel lymph node is the first lymph node in the chain of lymph nodes that drains fluid from the breast. It is usually found in the axilla (the armpit). If cancer is found in the axilla, it will usually be found in the sentinel node first.
All lymph nodes are surrounded by a thin layer of tissue called a capsule. Extranodal extension means that cancer cells within the lymph node have broken through the capsule and have spread into the tissue outside of the lymph node. Extranodal extension is important because it increases the risk that the tumour will regrow in the same location after surgery. For some types of cancer, extranodal extension is also a reason to consider additional treatment such as chemotherapy or radiation therapy.
In pathology, a margin is the edge of a tissue that is cut when removing a tumour from the body. The margins described in a pathology report are very important because they tell you if the entire tumour was removed or if some of the tumour was left behind. The margin status will determine what (if any) additional treatment you may require.
Most pathology reports only describe margins after a surgical procedure called an excision or resection has been performed to remove the entire tumour. For this reason, margins are not usually described after a procedure called a biopsy is performed to remove only part of the tumour. The number of margins described in a pathology report depends on the types of tissues removed and the location of the tumour. The size of the margin (the amount of normal tissue between the tumour and the cut edge) depends on the type of tumour being removed and the location of the tumour.
Pathologists carefully examine the margins to look for tumour cells at the cut edge of the tissue. If tumour cells are seen at the cut edge of the tissue, the margin will be described as positive. If no tumour cells are seen at the cut edge of the tissue, a margin will be described as negative. Even if all of the margins are negative, some pathology reports will also provide a measurement of the closest tumour cells to the cut edge of the tissue.
A positive (or very close) margin is important because it means that tumour cells may have been left behind in your body when the tumour was surgically removed. For this reason, patients who have a positive margin may be offered another surgery to remove the rest of the tumour or radiation therapy to the area of the body with the positive margin. The decision to offer additional treatment and the type of treatment options offered will depend on a variety of factors including the type of tumour removed and the area of the body involved. For example, additional treatment may not be necessary for a benign (non-cancerous) type of tumour but may be strongly advised for a malignant (cancerous) type of tumour such as invasive apocrine carcinoma.
If you received treatment (either chemotherapy or radiation therapy) before the tumour was removed, your pathologist will examine all of the tissue submitted to see how much of the tumour is still alive (viable). Lymph nodes with cancer cells will also be examined for treatment effects. A greater treatment effect (no or very few remaining viable tumour cells) is associated with better disease-free and overall survival.