Mr.Billfold
12-23-2007, 08:42 PM
STAGING THE MAST CELL TUMOR
In order for a rational therapeutic plan to be devised, the extent of tumor spread (or “stage of the tumor”) must be determined. Between the Stage and the Grade, a plan can be devised. The tumor is Staged 0 through IV as described below:
Stage 0: one tumor but incompletely excised from the skin
Stage I: one tumor confined to the skin with no regional lymph node involvement
Stage II: one tumor confined to the skin but with regional lymph node involvement present
Stage III: many tumors or large deeply infiltrating tumors, with or without lymph node involvement
Stage IV: any tumor with distant spread evident (this stage is further divided into substage a (no clinical signs of illness) and substage b (with clinical signs of illness)
In order to determine the tumor stage some probing of other lymphoid organs must be performed. Your veterinarian may recommend the following tests:
Basic Blood Work
A basic blood panel is part of this evaluation process and should be obtained at this point if it has not already been obtained. This testing will help show any factors that limit kidney or liver function and thus determine what drugs of chemotherapy can or cannot be used. It also will show if there are circulating mast cells in the blood (a very bad sign) or if anemia (low red blood cell count) is present which might related to the tumor.
Buffy Coat Smear/Bone Marrow Tap
The “buffy coat” is the small layer of white blood cells that floats atop the layer of red blood cells when a capillary tube of the patient’s blood has been centrifuged. This layer of cells can be smeared onto a microscope slide and checked for circulating mast cells. This process was once considered an important method of evaluating mast cell spread in dogs but has more recently been found not very helpful. This test is still of use for cats but has been supplanted by an actual bone marrow tap for dogs. The idea behind both of these tests was to determine the presence of malignant mast cells in the bone marrow (malignant cells circulating in the blood/found in the buffy coat would indicate malignant cells in the marrow).
Local Lymph Node Aspiration
The lymph nodes local to the site of the tumor should be aspirated (if they can be found) to see if the tumor has spread there.
Aspiration of the Spleen/Radiographs
The size of the spleen can be evaluated with radiographs but ultrasound guidance is generally needed to withdraw some cells for testing. The spleen is basically an organ of the lymph system and the presence of tumor in the deeper lymph organs such as the spleen and abdominal lymph nodes should be assessed. While the mast cell tumor does not spread to lung the way other tumors do, there are many lymph nodes in the chest and it is helpful to radiograph the chest to assess the size of these lymph nodes and thus help determine the extent of tumor spread.
OTHER FACTORS IN PROGNOSIS
As if Grade and Stage do not pose enough food for thought, there are other factors that add in to the prognosis.
ANATOMIC LOCATION: Mast Cell tumors arising in the following areas tend to be the most malignant: nail bed, genital areas, muzzle, and oral cavity. Mast cell tumors that originate in deeper tissues such as the liver or spleen carry a particularly grave prognosis.
GROWTH RATE OF TUMOR: Tumors that have been present for months or years tend to be more benign.
ARGYROPHILIC NUCLEAR STAINING ORGANIZING REGIONS (AgNORs): The pathologist can use a special silver stain on the tumor sample. The uptake of this stain correlates to the rapidity with which the tumor cells proliferate. The higher the AgNOR count, the more malignant the tumor.
There are other testing features that can be applied to the sample but, in general, the Grade, Stage, Location and symptoms of the patient help point to therapy.
THERAPY
Therapy for Mast Cell tumors consists of surgery, radiation therapy, and chemotherapy (as is the case for almost all types of cancer). What combination of the above is chosen depends on the extent of spread and malignant characteristics of the tumor.
SURGERY
If the tumor can be cured with one or even two surgeries, this is ideal. Mast Cell tumors are highly invasive and very deep and extensive margins (at least 3 cm in all directions) are needed. If for some reason, a grade I or II tumor cannot be completely excised, radiation therapy makes an excellent supplement.
RADIATION THERAPY
While radiation therapy tends to be expensive, the potential to permanently cure a grade I or II Mast Cell tumor is likely worth it. Radiation is a therapy most appropriate for localized disease. If the tumor stages so as to show more distant spread, radiation becomes less helpful and medications (chemotherapy) which can be delivered to the tumor through the patient’s own vasculature become needed.
In January 2004, Hahn, King and Carreras published a study where radiation therapy was used to treat incompletely removed Grade III mast cell tumors. They studied 31 dogs with Grade III mast cell tumors that did not show evidence of distant spread beyond the external area where the tumor was first detected. They treated these dogs with radiation sessions given three days a week for a total of 18 sessions. Approximately 65% of dogs acheived remission and 71% were alive one year after treatment. The median remission time was approximately 28 months, with dogs having ear, or genital tumors doing better than dogs with tumors in other locations. Dogs with tumors < or equal to 3 cm in diameter prior to surgery had a median survival time of 31 months. These are optimistic findings for the Grade III mast cell tumor, eventhough radiotherapy is an expensive treatment method.
In order for a rational therapeutic plan to be devised, the extent of tumor spread (or “stage of the tumor”) must be determined. Between the Stage and the Grade, a plan can be devised. The tumor is Staged 0 through IV as described below:
Stage 0: one tumor but incompletely excised from the skin
Stage I: one tumor confined to the skin with no regional lymph node involvement
Stage II: one tumor confined to the skin but with regional lymph node involvement present
Stage III: many tumors or large deeply infiltrating tumors, with or without lymph node involvement
Stage IV: any tumor with distant spread evident (this stage is further divided into substage a (no clinical signs of illness) and substage b (with clinical signs of illness)
In order to determine the tumor stage some probing of other lymphoid organs must be performed. Your veterinarian may recommend the following tests:
Basic Blood Work
A basic blood panel is part of this evaluation process and should be obtained at this point if it has not already been obtained. This testing will help show any factors that limit kidney or liver function and thus determine what drugs of chemotherapy can or cannot be used. It also will show if there are circulating mast cells in the blood (a very bad sign) or if anemia (low red blood cell count) is present which might related to the tumor.
Buffy Coat Smear/Bone Marrow Tap
The “buffy coat” is the small layer of white blood cells that floats atop the layer of red blood cells when a capillary tube of the patient’s blood has been centrifuged. This layer of cells can be smeared onto a microscope slide and checked for circulating mast cells. This process was once considered an important method of evaluating mast cell spread in dogs but has more recently been found not very helpful. This test is still of use for cats but has been supplanted by an actual bone marrow tap for dogs. The idea behind both of these tests was to determine the presence of malignant mast cells in the bone marrow (malignant cells circulating in the blood/found in the buffy coat would indicate malignant cells in the marrow).
Local Lymph Node Aspiration
The lymph nodes local to the site of the tumor should be aspirated (if they can be found) to see if the tumor has spread there.
Aspiration of the Spleen/Radiographs
The size of the spleen can be evaluated with radiographs but ultrasound guidance is generally needed to withdraw some cells for testing. The spleen is basically an organ of the lymph system and the presence of tumor in the deeper lymph organs such as the spleen and abdominal lymph nodes should be assessed. While the mast cell tumor does not spread to lung the way other tumors do, there are many lymph nodes in the chest and it is helpful to radiograph the chest to assess the size of these lymph nodes and thus help determine the extent of tumor spread.
OTHER FACTORS IN PROGNOSIS
As if Grade and Stage do not pose enough food for thought, there are other factors that add in to the prognosis.
ANATOMIC LOCATION: Mast Cell tumors arising in the following areas tend to be the most malignant: nail bed, genital areas, muzzle, and oral cavity. Mast cell tumors that originate in deeper tissues such as the liver or spleen carry a particularly grave prognosis.
GROWTH RATE OF TUMOR: Tumors that have been present for months or years tend to be more benign.
ARGYROPHILIC NUCLEAR STAINING ORGANIZING REGIONS (AgNORs): The pathologist can use a special silver stain on the tumor sample. The uptake of this stain correlates to the rapidity with which the tumor cells proliferate. The higher the AgNOR count, the more malignant the tumor.
There are other testing features that can be applied to the sample but, in general, the Grade, Stage, Location and symptoms of the patient help point to therapy.
THERAPY
Therapy for Mast Cell tumors consists of surgery, radiation therapy, and chemotherapy (as is the case for almost all types of cancer). What combination of the above is chosen depends on the extent of spread and malignant characteristics of the tumor.
SURGERY
If the tumor can be cured with one or even two surgeries, this is ideal. Mast Cell tumors are highly invasive and very deep and extensive margins (at least 3 cm in all directions) are needed. If for some reason, a grade I or II tumor cannot be completely excised, radiation therapy makes an excellent supplement.
RADIATION THERAPY
While radiation therapy tends to be expensive, the potential to permanently cure a grade I or II Mast Cell tumor is likely worth it. Radiation is a therapy most appropriate for localized disease. If the tumor stages so as to show more distant spread, radiation becomes less helpful and medications (chemotherapy) which can be delivered to the tumor through the patient’s own vasculature become needed.
In January 2004, Hahn, King and Carreras published a study where radiation therapy was used to treat incompletely removed Grade III mast cell tumors. They studied 31 dogs with Grade III mast cell tumors that did not show evidence of distant spread beyond the external area where the tumor was first detected. They treated these dogs with radiation sessions given three days a week for a total of 18 sessions. Approximately 65% of dogs acheived remission and 71% were alive one year after treatment. The median remission time was approximately 28 months, with dogs having ear, or genital tumors doing better than dogs with tumors in other locations. Dogs with tumors < or equal to 3 cm in diameter prior to surgery had a median survival time of 31 months. These are optimistic findings for the Grade III mast cell tumor, eventhough radiotherapy is an expensive treatment method.