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cutoff value is not known. Ki67 staining is also associated with prognosis.
· KIT labelling pattern appears to be associated with prognosis as for dogs
· Multiple lesions: Unlike in dogs, multiple cutaneous tumours are associated with splenic involvement and worse outcomes than solitary tumours in cats in some studies, though other studies found no effect on prognosis.
· HIstologic margins may not predict recurrence, though evaluation of this factor in a group of ‘high- risk’ MCT may be of more clinical significance.
· Recurrent tumours may be associated with a worse prognosis
I currently recommend evaluation of local lymph nodes in every cat and abdominal ultrasound and buffy
coat assessment in cats with multiple or high mitotic index MCT. For tumours with aggressive growth, more aggressive surgery is warranted, but given the benign behaviour of the majority of feline cutaneous MCT surgical margins of 1-2 cm seem reasonable.
· Splenic MCT may be solitary or associated with cutaneous tumours. Involvement of the liver
and bone marrow/peripheral blood is common. Splenectomy is the treatment of choice, even if liver involvement or mastocytemia is documented, as it is associated with the longest survival times (> 1 year median). The addition of chemotherapy should be considered for cats with evidence of more distant disease (liver involvement, persistent mastocytemia), though the best protocol, and whether or not it impacts outcome, is not known.
· Intestinal: Prognosis was previously thought to be poor because of extensive disease at diagnosis but a recent study suggests that the behaviour of these tumours is extremely variable. Based on this, my current recommendation is for surgical excision if possible. Chemotherapy could be considered for metastatic or unresectable tumours.
Systemic treatment in feline MCT:
Response rates of approximately 50-80% to CCNU and to toceranib are reported, and there are anecdotal/ case reports of responses to other such as vinblastine, chlorambucil and imatinib. For cats with gross disease, it would seem reasonable to start with CCNU or toceranib and consider the other drugs as alternatives if a good response was not seen.
References:
· In my practice, complete staging involves evaluation of local/draining lymph nodes, abdominal ultrasound with liver and spleen cytology, and bone marrow evaluation. Bone marrow is typically reserved
Your Singapore, the Tropical Garden City
WSV18-0151
ONCOLOGY
CURRENT TREATMENT OPTIONS FOR MAST CELL TUMORS IN DOGS AND CATS
S. Ryan1, C. Cannon1
1The University of Melbourne, UVet Hospital, Werribee, Australia
CURRENT TREATMENT OPTIONS FOR MAST CELL TUMOURS IN DOGS AND CATS
Claire Cannon BVSc (hons) DACVIM (Oncology) MANZCVS
Stewart Ryan BVSc (hons) MS DACVS MANZCVS University of Melbourne U-Vet Animal Hospital claire.cannon@unimelb.edu.au stewart.ryan@unimelb.edu.au
Learning objectives: Understand the perioperative management, staging and surgical oncology principles for cutaneous MCT in dogs and cats, and the indications for adjunctive radiation therapy or chemotherapy in conjunction with surgery. Understand treatment options for non-resectable MCTs.
Canine cutaneous MCTs: Diagnosis:
· Cytology is usually diagnostic, and finding of suspected high grade MCT on cytology is highly predictive for histologic high grade.
  1. Krick EL, Billings AP, Shofer FS, Watanabe S, Sorenmo KU Cytological lymph node evaluation in dogs with mast cell tumours: association with grade and survival Vet Comp Oncol 2009;7:130-138
2. Weishaar KM, Thamm DH, Worley DR, Kamstock DA Correlation of nodal mast cells with clinical outcome in dogs with mast cell tumour and a proposed classification system for the evaluation of node metastasis J Comp Pathol 2014;151:329-338
3. Kry KL, Boston SE. Additional local therapy with primary re-excision or radiation therapy improves survival and local control after incomplete or close surgical excision of MCTs in dogs Vet Surg 2014;43:182-189
4. Miller RL, van Lelyveld S, Warland J, Dobson JM, Foale RD A retrospective review of treatment and response of high-risk MCTs in dogs Vet Comp Oncol 2016;14:361-370
· Lymph node (LN) evaluation is always recommended because low-grade MCT may metastasise. MCTs affecting the muzzle and perioral tissues may be more likely to metastasise. LN mapping is ideal to identify the ‘sentinel’ node. Diagnosis of metastasis from both cytology and histology can be challenging, but criteria have been recently published that may assist (1, 2). Good outcomes can be achieved with aggressive treatment in low grade, stage 2 MCT so identifying metastatic LN prior to surgery is important. Abdominal ultrasound and liver and spleen cytology is recommended in cases of known or suspected high grade tumours or when grade is unknown and local therapy is likely to be radical.
· Histology: The 2-tier histologic grading scheme (low/ high grade) has better inter-pathologist agreement than the 3-tier scheme, however combining the two may give additional information. Mitotic index (per 10 high power fields) is i prognostic, though the most useful value is not fully determined. The significance of additional prognostic factors (Ki67, AgNORs, c-kit staining pattern and mutation) is, in my opinion, not fully determined in terms of effect on prognosis.
for cases with CBC abnormalities because it is uncommon (< 5%).
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