Sky's Mast Cell Tumors: Diagnosis, Surgery, and Chemotherapy with Kinavet-CA1

Sky was diagnosed with Mast Cell Tumors on 8/14.

In July, I found a lump on Sky's rear left leg. It looked like a marble was just under her skin. The hair had come off of it and it had a moist brown crust. It was flesh colored and felt like it was soft and mushy. I'd never seen anything like it. This is on the outside of her left leg, near her knee.

So I took her to the vet on 7/15. Sky had chewed on it in the mean time, so it looked a little scabby in places when we went to the vet. I thought her allergies were acting up, she was scratching and chewing like crazy. (I've since found out that Mast Cell Tumors release histamines, which were making her itchy all over.) So she got the e-collar at that point. But she still scratched until she bled. The vet tried to get a fine needle aspirate, but couldn't get anything out of it. So she prescribed an antibiotic for 10 days, which did nothing. So we scheduled surgery for 8/10 to remove it. The night before her surgery, I found another lump on her right side where her waist dips in. My vet calls that her flank. This growth was smaller (no picture). The vet removed both and sent the one from her leg to the lab to be analyzed. Her leg wound got six stitches.

Her flank got five stitches.

The lab results came in on 8/14 (shown with my highlights for emphasis):

Microscopic Interpretation (Biopsy)

Cutaneous mast cell tumor, Patnaik grade 2 (low mitotic index), ulcerated and severely inflamed

Two tier histologic grading = low grade

Mitotic index = one (total mitotic figures counted in ten equivalent 400x high power fields).

Margins = this mast cell tumor forms a loosely circumscribed, base heavy nodule within the dermis and subcutis, 11 x 8 mm; it appears to be completely excised, closest approach to deep central margin is 1.0 mm, and the nearest lateral margin is approximately 2.0 mm.

Comments:

This inflamed mast cell tumor is classified as a grade 2 or intermediate grade tumor based upon the Patnaik grading system (1=low grade, 2=intermediate grade, 3=high grade).

Also, utilizing the recently proposed two tier histologic grading system for canine cutaneous mast cell tumors, this would be categorized as LOW grade mast cell tumor (see Vet Pathol Jan 2011: 48(1):147-155). Median survival time for high grade MCTs on this system was less than 4 months, while the median survival time for low grade tumors was not reached after 2 years of follow-up.

Histological grading may be the most important prognostic indicator overall but other clinical factors specific to each patient need to be considered as well. Negative prognostic factors include signs of systemic illness; rapid growth of tumor; and recurrent growth. Wide surgical excision with 2-3 cm lateral margins and 1 fascial plane is the standard recommendation for removal of MCTs. However, tumor recurrence and/or metastases were not observed with lateral margins of 10 mm and deep margins of 4 mm in one recent study (JAVMA 2011, 239,11:1464-1469).

Furthermore, it has recently been shown to that mitotic index is an important prognostic indicator, regardless of the grade (see Vet Pathol 2007 May 44 (3):335-41). For grade 2 mast cell neoplasms with mitotic index greater than five, median survival was five months, whereas tumors with mitotic index less than or equal to five, the median survival with longer than 70 months. This mast cell neoplasm has a low mitotic index, suggesting more favorable prognosis.

Assessment of these factors will dictate if any additional diagnostic tests may be required and will determine which therapeutic option (further surgery, radiation, chemotherapy) is best suited for your patient.

Approximately 15% of dogs will demonstrate multiple cutaneous mast cell tumors, either concurrently or sequentially. Though the current WHO staging of canine cutaneous mast cell tumors considers multicentricity a negative prognostic indicator, other studies have failed to demonstrate a difference in outcome for patients with multiple tumors (see JAVMA 2006;228:91-95).

 
 OK. So, Mast Cell Tumors are bad news, but it could be worse... The lab results give me reason to hope. There is a contradiction. It states that "negative prognostic factors include... recurrent growth." But then in states that "...studies have failed to demonstrate a difference in outcome for patients with multiple tumors."


We were supposed to return to the vet 10 days after surgery (8/19) to have the stitches removed. But I found another tumor on the night of 8/17 on her right shoulder. This one is even smaller than the other two. I wouldn't have found it if I hadn't been looking. It did have the same moist brown crust as the one on her leg, so I was pretty sure it was also a Mast Cell Tumor.

On 8/18, I arranged for another surgery on 8/19, instead of just going in for removal of the stitches. The vet would cut out the tumor and remove the stitches from the first two tumors while she was under anesthetic. Good thing for the anesthesia... The area where Mast Cell Tumors are removed often don't heal very quickly and sure enough, the wounds hadn't healed. So the vet stapled all three wounds with an abundance of staples. Leg:

Side (she jumped out of the car before I could lift her down, causing a little bit of bleeding. She's a Houdini. If she sees an inch of daylight, she's going for it!):

Shoulder:

 I count more than 50 staples... Poor girl. The e-collar is to keep her from chewing her leg and side. The t-shirt is to keep her from scratching her shoulder. (She's in a size 4T thrift store $1 t-shirt...) There's a shaved spot on her front right leg where she had an IV during the surgery. She is still just as cute and as happy as can be!

Sky's t-shirt is a rainbow smiley face with hearts and peace signs. She's so fashionable!

I have decided to give her Chemotherapy. I have always said that I'd never do Chemotherapy for a dog. But she can't live with these tumors since they cause her to scratch until she bleeds. And I don't want to keep subjecting her to surgery. So, the way I see it, my choices are Chemotherapy, or put her down. So, I'm going with the Chemotherapy, especially since the lab results show that she could have a good outcome and the chemotherapy looks so promising. Kinavet is a fairly new drug which inhibits the thing that causes the tumors. It can shrink and get rid of these tumors. Check out Oz's story. My vet had to order the Kinavet. I just picked it up on 8/21 and gave her the first dose with her dinner.

I'm supposed to give her two pills once a day. The pills are coated, but there's still a warning to wash with soap and water after handling the pills. And if I need to clean up her feces, urine, or vomit, I have to wear gloves (I guess since there's no protection from the pill coating once it's been ingested.) One month of pills is $138. She has to have blood work done every two weeks. There are a bunch of life-threatening adverse reactions that could result from this therapy, so she will need to be closely monitored. The vet said she could be on this drug for 6 months to lifetime. Sky is only 10 years old, she could have many more good years left in her...

I'm not sure what the cost is at this point. I'm missing a receipt for the first surgery. I know how much that was, but I also had her teeth cleaned while she was under and her nails clipped. So I don't want to include those expenses... I'll post when I find that receipt...

I'm optimistic at this point. The lab analysis points to a good outcome. We just need her to tolerate it well (no vomiting or diarrhea) and none of those life-threatening adverse reactions. So far she seems fine after her first dose last night. I'd love to hear from anyone who has experience with these tumors or this drug. You can leave a comment even if you don't have an account. It would just be from 'anonymous' but you can put whatever name you want as a signature in your comment...