by Jason Wasserman MD PhD FRCPC
August 21, 2023
Carcinoma ex pleomorphic adenoma is a type of salivary gland cancer that develops from within a previously noncancerous tumour called pleomorphic adenoma.
In pathology, carcinoma is a general term used to describe a group of cancerous tumours made up of epithelial cells while “ex” means “out of” or “from”. Pleomorphic adenoma is a noncancerous tumour and the most common type of salivary gland tumour in adults. Put together, carcinoma ex pleomorphic adenoma is a cancerous tumour made up of epithelial cells developing from a pleomorphic adenoma.
Most carcinoma ex pleomorphic adenomas are found in the parotid gland, however, any of the salivary glands including the minor salivary glands in the oral cavity can be involved.
The most common symptom of carcinoma ex pleomorphic adenoma is the sudden growth of a tumour that has been present for many months or years. Additional symptoms include pain and weakness in the area of the tumour.
Carcinoma ex pleomorphic adenoma arises from a preexisting pleomorphic adenoma. At present, we do not know why some pleomorphic adenomas undergo this change while others do not.
Any type of salivary gland cancer can develop from within a pleomorphic adenoma. However, the most common types of cancers associated with pleomorphic adenoma are:
Carcinoma ex pleomorphic adenoma is described as intracapsular when all of the malignant (cancerous) cells are found within the capsule (border) of the previously benign (noncancerous) pleomorphic adenoma. Intracapsular means that the cancerous cells have not yet spread into the surrounding tissue. Compared with minimally invasive and invasive tumours (see below), intracapsular tumours are less likely to spread to lymph nodes are other parts of the body and are typically cured by surgery alone.
Carcinoma ex pleomorphic adenoma is described as in situ if all of the malignant (cancerous) cells are found within round structures called ducts and the ducts are located entirely within the capsule (border) of the previously benign (noncancerous) pleomorphic adenoma. Another term used to describe an in situ tumour is non-invasive. Compared with minimally invasive and invasive tumours (see below), in situ tumours are less likely to spread to lymph nodes are other parts of the body and are typically cured by surgery alone.
Carcinoma ex pleomorphic adenoma is described as minimally invasive when the malignant (cancerous) cells have spread no more than 4 to 6 mm past the capsule (border) of the previously benign (noncancerous) pleomorphic adenoma and into the surrounding tissue. Compared with invasive tumours (see below), minimally invasive tumours are associated with better overall prognosis.
Carcinoma ex pleomorphic adenoma is described as invasive when the malignant (cancerous) cells have spread more than 6 mm past the capsule (border) of the previously benign (noncancerous) pleomorphic adenoma and into the surrounding tissue. Compared with intracapsular and minimally invasive tumours (see above), invasive tumours are more likely to spread to lymph nodes and are associated with a worse overall prognosis.
Lymphovascular invasion (LVI) means that cancerous 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 cancerous cells can use blood vessels or lymphatic vessels to spread to other parts of the body such as lymph nodes or the lungs. If lymphovascular invasion is seen, it will be included in your report. The risk of lymphovascular invasion depends on the type of cancer developing within a pleomorphic adenoma (see above).
Perineural invasion (PNI) is a term pathologists use to describe cancerous cells attached to or inside a nerve. A similar term, intraneural invasion, is used to describe cancer cells inside a nerve. Nerves are like long wires made up of groups of cells called neurons. Nerves are found all over the body and they are responsible for sending information (such as temperature, pressure, and pain) between your body and your brain. Perineural invasion is important because the cancerous cells can use the nerve to spread into surrounding organs and tissues. This increases the risk that the tumour will regrow after surgery. If perineural invasion is seen, it will be included in your report.
Lymph nodes are small immune organs found throughout the body. Cancerous cells can spread from a tumour to lymph nodes through small vessels called lymphatics. The risk of cancerous cells spreading to a lymph node depends on the type of cancer found in the pleomorphic adenoma. For this reason, lymph nodes are not always removed at the same time as the tumour. However, when lymph nodes are removed, they will be examined under a microscope and the results will be described in your report.
Cancerous 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 cancerous cells in the lymph node. 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 cancerous cells. If cancerous 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 cancerous cells in a lymph node increases the risk that cancerous 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 cancerous cells. For example, a lymph node that contains cancerous 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 cancerous cells. For example, a lymph node that does not contain cancerous cells may be called “negative for malignancy” or “negative for metastatic carcinoma”.
All lymph nodes are surrounded by a thin layer of tissue called a capsule. Extranodal extension means that cancerous 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 for the purpose of removing the entire tumour. For this reason, margins are not usually described after a procedure called a biopsy is performed for the purpose of removing 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) also 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.