by Jason Wasserman MD PhD FRCPC
June 5, 2022
Intestinal-type adenocarcinoma (ITAC) is a type of head neck cancer. The tumour starts from the tissue that lines the inside of the nasal cavity or the paranasal sinuses such as the ethmoid or maxillary sinus. ITAC is an aggressive type of cancer that quickly spreads into other parts of the head including the space around the eyes and the brain.
Most patients who develop ITAC have a history of working with wood dust, leather dust, textile dust, or formaldehyde for a prolonged period of time. These chemicals damage the tissue on the inside of the nasal cavity and paranasal sinuses which can lead to the development of cancer.
The diagnosis of ITAC is usually made after a small sample of tissue is removed in a procedure called a biopsy. The diagnosis can also be made after the entire tumour is removed in a procedure called a resection. The tissue is then sent to a pathologist who examines it under a microscope.
Before making the diagnosis of ITAC, your pathologist will likely review your medical record, in particular any recent imaging studies that were done to confirm that you do not have a history of gastrointestinal cancer (especially colon cancer) and that are no suspicious masses in your gastrointestinal tract. This information is important because a metastasis from a gastrointestinal tumour can look the same as intestinal-type adenocarcinoma under the microscope and metastases must be ruled out before making the diagnosis of ITAC.
When examined under the microscope, the tumour looks very similar to a type of cancer that normally develops in the colon called adenocarcinoma (which is why the tumour is called “intestinal-type”). The tumour cells often connect together to form round structures called glands or long finger-like projections called papillae. The glands may be arranged in a back-to-back manner that pathologists describe as cribriform. A type of cell death called necrosis is commonly seen, especially on the inside of the glands. Pathologists use the term “dirty necrosis” to describe this type of cell death.
Your pathologists may perform a test called immunohistochemistry to confirm the diagnosis. When performed, the tumour cells in ITAC are usually positive for markers normally seen in the colon including CK20, CDX-2, and villin. The tumour cells may also be positive for CK7, another marker often seen in the digestive tract.
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 a term pathologists use to describe tumour cells attached to a nerve. Perineural invasion is important because the tumour cells can use the nerve to spread into surrounding tissues. This increases the risk that the tumour will re-grow after treatment.
Blood moves around the body through long thin tubes called blood vessels. Another type of fluid called lymph which contains waste and immune cells moves around the body through specialized vessels called lymphatics. The term lymphovascular invasion is used to describe tumour cells that are found inside a blood or lymphatic vessel. Lymphovascular invasion is important because these cells are able to metastasize (spread) to other parts of the body such as lymph nodes or the lungs.
A margin is any tissue that was cut by the surgeon in order to remove the tumour from your body. Whenever possible, surgeons will try to cut tissue outside of the tumour to reduce the risk that any cancer cells will be left behind after the tumour is removed.
The types of margins described in your report will depend on the parts of the sinonasal tract involved and the type of surgery performed. Margins are usually only described in your report after the entire tumour has been removed.
A negative margin means that no tumour cells were seen at any of the cut edges of tissue. A margin is called positive when there are tumour cells at the very edge of the cut tissue. A positive margin is associated with a higher risk that the tumour will recur in the same site after treatment.
Because ITAC is often removed in multiple pieces, your pathologist may not be able to reliably assess the margins of the tumour. For that reason, most pathology reports for ITAC do not have information about margins.
Lymph nodes are small immune organs located throughout the body. Tumour cells can travel from the tumour to a lymph node through lymphatic channels located in and around the tumour (see Lymphovascular invasion above). The movement of tumour cells from the tumour to a lymph node is called metastasis.
Lymph nodes from the neck are sometimes removed at the same time as the main tumour in a procedure called a neck dissection. The lymph nodes removed usually come from different areas of the neck and each area is called a level. The levels in the neck include 1, 2, 3, 4, and 5. Your pathology report will often describe how many lymph nodes were seen in each level sent for examination. Lymph nodes on the same side as the tumour are called ipsilateral while those on the opposite side of the tumour are called contralateral.
Your pathologist will carefully examine each lymph node for tumour cells. Lymph nodes that contain tumour cells are often called positive while those that do not contain any tumour cells are called negative. Most reports include the total number of lymph nodes examined and the number, if any, that contain tumour cells.
A group of tumour cells inside of a lymph node is called a tumour deposit. If a tumour deposit is found, your pathologist will measure the deposit and the largest tumour deposit found will be described in your report. Larger tumour deposits are associated with a worse prognosis. The size of the largest tumour deposit is also used to determine the nodal stage (see Pathologic stage below).
The pathologic stage for ITAC is based on the TNM staging system, an internationally recognized system originally created by the American Joint Committee on Cancer. This system uses information about the primary tumour (pT), lymph nodes (pN), and distant metastatic disease (pM) to determine the complete pathologic stage (pTNM). Your pathologist will examine the tissue submitted and give each part a number. In general, a higher number means more advanced disease and a worse prognosis.
These tumours are given a tumour stage between 1 and 4. The tumour stage is based on how far the tumour has spread outside of the nasal cavity or ethmoid sinus.
These tumours are given a tumour stage between 1 and 4. The tumour stage is based on how far the tumour has spread outside of the maxillary sinus.
These tumours are given a nodal stage between 0 and 3 based on the following three features:
The nodal stage will be higher if any of the tumour deposits are larger than 3 cm, more than one lymph node contains cancer cells, cancer cells are found in lymph nodes on both sides of the neck, and if any of the lymph nodes show extranodal extension.
If no cancer cells are found in any of the lymph nodes examined, the nodal stage is N0. If no lymph nodes are submitted for pathological examination, the nodal cannot be determined and the stage is listed as NX.
Intestinal-type adenocarcinoma is given a metastasis stage (pM) of 0 or 1 based on the presence of cancer cells at a distant site in the body (for example the lungs). The metastatic stage can only be determined if tissue from a distant site is submitted for pathological examination. Because this tissue is rarely present, the metastasis stage cannot be determined and is listed as MX.