This article will help you read and understand your pathology report for chondrosarcoma.
by Bibianna Purgina, MD FRCPC, updated on July 30, 2020
Cartilage is a special ‘elastic’ type of tissue which means that can be bent or compressed (put under pressure) without breaking. Cartilage is found throughout the body although most cartilage is found between bones where it helps form a cushion that protects the ends of the bones from damage. Some parts of the body, such as the nose and ears, are made almost entirely out of cartilage. The cells that make up cartilage are called chondrocytes.
Chondrosarcoma is a type of cancer called a sarcoma. Sarcomas are cancers that develop from mesenchymal tissues such as cartilage, fat, bone, and muscle. Chondrosarcoma develops from cartilage.
Chondrosarcomas can start within a bone or any other part of the body where cartilage is normally found such as the nose or ears. The most common locations for chondrosarcoma are the spine and pelvis. It typically affect older adults and it is the second most common type of bone sarcoma.
This diagnosis is usually made after a small sample of tissue is removed in a procedure called a biopsy. The biopsy is sent to a pathologist who examines the tissue under a microscope. Another surgery is then performed to remove the entire tumour which will also be sent to a pathologist for examination. Some patients will be offered radiation and/or chemotherapy before surgery.
There are different types of chondrosarcoma and each one is called a histologic type. The histologic type is based on the way the cells look and where on the bone the tumour is growing. Your pathologist will determine the histologic type of your tumour after examining it under the microscope.
Histologic types of chondrosarcoma include:
The most common histologic type of chondrosarcoma is conventional chondrosarcoma. A dedifferentiated chondrosarcoma is a conventional chondrosarcoma that has changed into a high grade sarcoma (pathologists call this kind of change ‘transformation’).
The histologic type of chondrosarcoma is important because it is used to determine the tumour grade (see Histologic grade below). Some types of chondrosarcoma, such as the mesenchymal and dedifferentiated types, are always given a higher grade and are associated with worse prognosis.
Grade is a way of comparing cancer cells with normal, healthy cells. Your pathologist can only determine the grade of your tumour after examining a tissue sample under the microscope.
For most chondrosarcomas, the grade ranges from 1 (low) to 3 (high). Grade 1 cells look the most like normal cartilage while grade 3 cells look the least like normal cartilage.
However, some histologic types are always given the same grade. For example, clear cell chondrosarcoma is always a grade 1 (low grade) tumour. In contrast, mesenchymal and dedifferentiated chondrosarcomas are always grade 3 (high grade).
If you were diagnosed with a conventional chondrosarcoma, your pathologist will closely examine the tumour for three microscopic features in order to determine the grade:
A grade is then given to the tumour as follows:
Grade is important because it is used to predict the behavior of the tumour. For example, grade 1 tumours may come back in the same location (local recurrence) but it is rare for them to spread to more distant parts of the body. The movement of cancer cells to another part of the body is called metastasis. Higher grade tumours (grade 2 and 3) are more likely to spread to distant parts of the body and are usually associated with worse prognosis.
These tumours are measured in three dimensions but only the largest dimension is typically included in the report. For example, if the tumour measures 5.0 cm by 3.2 cm by 1.1 cm, the report may describe the tumour size as 5.0 cm in greatest dimension.
The tumour size is important because it is used to determine the tumour stage (see Pathologic stage below). Larger tumours are more likely to spread to other parts of the body. The movement of tumour cells to another part of the body is called metastasis.
Some larger chondrosarcomas may break through the bone and grow into the surrounding tissue including muscle, tendons, or the joint space. If this has occurred, it may be included in your report and is usually described as extraosseous extension.
Some bones are made up of multiple parts. If the chondrosarcoma has grown from one part into another, your report will describe the tumour as invading adjacent bones.
Tumour extension is used to determine the tumour stage (see Pathologic stage below). This is particularly important for tumours in the spine or pelvis as both of these bones are made up of multiple parts.
Nerves are like long wires made up of groups of cells called neurons. Nerves send information (such as temperature, pressure, and pain) between your brain and your body. Perineural invasion means that cancer cells were seen attached to a nerve.
Cancer cells that have attached to a nerve can use the nerve to travel into tissue outside of the original tumour. This increases the risk that the tumour will come back in the same area of the body (recurrence) after treatment. However, perineural invasion is not commonly seen in chondrosarcoma.
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 lymphatic channels.
Cancer cells can use blood vessels and lymphatics to travel away from the tumour to other parts of the body. The movement of cancer cells from the tumour to another part of the body is called metastasis.
Before cancer cells can metastasize, they need to enter a blood vessel or lymphatic. This is called lymphovascular invasion.
Lymphovascular invasion increases the risk that cancer cells will be found in a lymph node or a distant part of the body such as the lungs. However, chondrosarcoma rarely shows lymphovascular invasion.
A margin is any tissue that was cut by the surgeon to remove the bone (or part of the bone) and tumour from your body. Depending on the type of surgery you have had, the types of margins, which could include proximal (the part of the bone closest to the middle of your body) and distal (the part of the bone farthest from the middle of your body) bone margins, soft tissue margins, blood vessel margins, and nerve margins.
All margins will be very closely examined under the microscope by your pathologist to determine the margin status. A margin is considered negative when there are no cancer cells at the edge of the cut tissue. A margin is considered positive when there are cancer cells at the 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 (local recurrence).
Lymph nodes are small immune organs located throughout the body. Cancer 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 cancer cells from the tumour to a lymph node is called a metastasis.
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 cancer cells. Lymph nodes that contain cancer cells are often called positive while those that do not contain any cancer cells are called negative. Most reports include the total number of lymph nodes examined and the number, if any, that contain cancer cells.
Lymph nodes are used to determine the nodal stage (see Pathologic stage below). The tumour cells in a chondrosarcoma rarely travel to a lymph node.
The pathologic stage for chondrosarcoma 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 (T), lymph nodes (N), and distant metastatic disease (M) 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 worse prognosis.
The pathologic stage will only be included in your report after the entire tumour has been removed. It will not be included after a biopsy.
Tumour stage (pT) for chondrosarcoma
For bone cancers such as chondrosarcoma, the primary tumour (pT) stage depends on where the tumour was located in your body.
Tumours in appendicular skeleton
These are bones of your appendages, and include the arms, legs, shoulder, trunk, skull, and facial bones. A tumour from these region is given a tumour stage from 1-3 based on tumour size whether there a separate tumor nodule(s).
Tumours in the spine
Tumours located in the spine are given a tumour stage from 1-4 based on the extent of tumor growth.
Tumours in the pelvis
Tumours located in your pelvis are given a tumour stage from 1-4 based on the size of the tumour and extent of tumor growth.
If after microscopic examination, no tumour is seen in the resection specimen sent to pathology for examination, it is given the tumour stage pT0 which means there is no evidence of primary tumour.
If your pathologist cannot reliable evaluate the tumor size or the extent of growth, it is given the tumour stage pTX (primary tumour cannot be assessed). This may happen if the tumour is received as multiple small fragments.
Nodal stage (pN) for chondrosarcoma
Primary bone cancers including chondrosarcoma are given an nodal stage of 0 or 1 based on finding cancer cells in one or more lymph nodes.
Metastasis stage (pM) for chondrosaroma
Primary bone cancers including chondrosarcoma are given a metastatic stage only if the presence of metastasis has been confirmed by a pathologist. There are two metastatic stages in primary bone sarcomas, M1a and M1b. If there are confirmed lung metastasis, then the tumor metastatic stage is 1a.
The metastatic stage can only be given if tissue from a distant site is sent for pathological examination. Because this tissue is rarely present, the metastatic stage cannot be determined, and it is typically not included in your report.