Surgery remains one of the best ways to treat many kinds of cancer. Surgery cures more cancer than any other single modality. It is important however that before surgery is performed, we gather as much information as possible to determine whether surgery is going to be beneficial. It is important to stage the tumor and make a diagnosis of the type of cancer where possible prior to surgery.
What is tumor staging?
Put simply, we need to know the type of cancer, whether it is benign or malignant, whether it has spread and where it has spread to.
In a more complex explanation, we need to know the type, histological grade and clinical TNM.
How do you stage a tumor?
It is important to biopsy the mass for diagnosis and grading. It may then be necessary to do blood tests including a complete blood count, biochemistry profile and urinalysis. Thoracic radiographs are important as well as abdominal ultrasound to look for evidence of metastasis. Sentinel lymph node mapping is also recommended for many kinds of cancer. Needle biopsies of lymph nodes are very inaccurate and it is often necessary to remove the draining lymph node at the time of surgery so it is important to know which lymph node to remove.
The most important factor for staging a local tumor is the size of the mass. Tumor diameter (or size) is important for prognosis.
Tumor staging therefore involves identifiying the type, the size, sentinel lymph node involvement and whether distant metastasis (spread of cancer) to other organs has occurred.
What is tumor grading?
Essentially this is a classification of how aggressive an individual tumor may be. Some cancers although nasty by definition may have a low grade and are less likely to spread and therefore the prognosis with surgery may be good. Alternatively, some cancers may be extremely aggressive and have a high grade and it is possible that it may be too late for a surgical cure alone and adjunct therapies like chemotherapy may be required. This may change the owners opinion of whether to move forward with surgery for their pet.
At Treendale Pet Medical, we would like to give you as much information about the tumor as possible before we launch into surgery. A diagnosis, grade and staging is important to give your pet the best chance at survival but equally to avoid disappointment and unneccary expense.
What is a tumor biopsy?
A biopsy is simply taking a piece of the mass or some cells from the mass to make a diagnosis of what type of cancer it is.
How do you do a cancer biopsy?
The type of biopsy technique depends primarily on the location of the mass and the veterinarian's experience and clinical suspicion. Many skin cancers can have a fine needle biopsy. This is simple and fast and involves having a few cells suctioned from the tumor using a syringe and small needle. Oral cancers and sarcomas often do not exfoliate well so a small piece of tissue is required for histopathology and diagnosis. At Treendale we do needle biopsies, punch biopsies and incisional wedge biopsies to take a small piece of tissue to send to a pathologist for a diagnosis and grading of the tumor. Sometimes this can be done under local anaesthetic.
If the cancer is internally located such as the lungs, liver or other internal organs, biopsy is more challenging. Ultrasound guided needle biopsies or surgical biopsies may be required in this case. Some cancers can be biopsied endoscopically eg stomach and colon.
What is the difference between a benign and a malignant tumor?
A benign tumor essentially doesn't spread and is less life threatening. Benign tumors tend to grow where they are located but do not send out seeds to start growing in other organs. They are usually curable with surgical removal depending of course where they may be located.
What is TNM staging for tumors in animals?
T = Tumor
T0 - No evidence of neoplasia
T1 - Tumor <1cm diameter not invasive
T2 - Tumor 1-3 cm diameter, locally invasive
T3 - Tumor >3cm diameter or evidence of of ulceration or local invasion
N = Node
N0 - No evidence of nodal involvement
N1 - Node enlarged
N2 - Node enlarged and fixed to surrounding tissues
N3 - Nodal involvement beyond the first station
M = Metastasis
M0 - No evidence of metastasis
M1 - metastasis to one organ system eg lungs
M2 - Metastasis to more than one organ system eg lungs AND liver
CURATIVE INTENT SURGERY
After gathering as much information as we can, we make a decision whether the cancer can be cured surgically. It is important for our clients to know whether this is going to work or at least how long the pet might have to make informed decisions. Sometimes a cure can be combined with a combination of surgery and chemo or radiation.
If the cancer is curative, it is crucial that we do everything correctly to make sure we get all of the cancer and don't accidentally spread the cancer with poor surgical technique and spilling or handling the cancer cells and spreading it inappropriately. We work hard on correct surgical principles to maximise success.
What is a surgical margin?
- the tumor should be draped off from the rest of the surgical field
- adequate surgical margins are crucial to prevent regrowth
- all biopsy tracts need to be resected
- the surgeon must be careful not to handle any ulcerated tumor to prevent spreading of cancer cells
- adequate closure of dead space is important to prevent seroma formation and spread of cancer cells
- we use a new set of gloves and surgical instruments to close the wound so there is no contamination of healthy tissue with cancer cells
A surgical margin is an area of tissue around a cancer (tumor). With curative intent surgery, the surgery aims to get all of the cancer and prevent regrowth by having a surgical margin of normal tissue around the tumor. The margin required for curative intent surgery differes with different tumors. A benign fatty lump (lipoma) can be removed with a narrow margin of 1 cm. Soft tissue sarcomas however may need a wide excision of 3cm of normal tissue around the tumor. This is why a biopsy and grading should really be done prior to curative intent surgery to make sure adequate margins of normal tissue are removed to prevent cancer regrowth.
What is a clean surgical margin?
A clean surgical margin means the tumor has been completely removed. There is an adequate margin of normal tissue around the edges of the tumor. The cancer has been completely removed and no cells have been left behind.
What is a dirty surgical margin?
A dirty margin means cancer cells can be seen extending to the edge of the tissue removed. The lumps are sent to a pathologist who makes slides of the tumor and surrounding tissue and examines it under a microscope. If the pathologist can see cancer cells extending to the edge of the tissue, we have a "dirty margin". This means that cancer cells have been left behind in the patient and there is a risk of regrowth or metastasis. The surgeon and clients would then need to make a decision about taking the patient back to surgery to take more tissue away. This is obviously frustrating for all concerned. This is also why it is best to diagnose, grade and stage the cancer prior to surgery.