Abstract. Ten veterinary pathologists independently assigned histologic grades to the same 60 canine cutaneous mast cell tumors using the Patnaik classifications. The degree of agreement in grading among the pathologists was compared with the degree of agreement among the same pathologists in a previous study, in which each pathologist used the reference for grading that he/she uses routinely. Mean agreement improved significantly from 50.3% to 62.1% with uniform use of the Patnaik classifications (P ϭ 0.00001), suggesting that there is value in uniform application of a single grading scheme for canine cutaneous mast cell tumors. Agreement among pathologists was still not 100%, suggesting that a more objective grading scheme should be developed and that other histologic indicators of prognosis should be investigated.Key words: Dogs; grade; histopathology; mastocytoma.Mast cell tumors (MCTs) are the most common cutaneous tumors of the dog. 13 These tumors vary widely in their behavior, from nearly benign to highly invasive and metastatic. It has been recognized for more than 30 years that histologic grading is prognostic for the behavior of canine cutaneous MCTs. 3,6,10 The 2 most widely recognized grading systems classify MCTs into 3 grades based on histologic characteristics, including cellularity, cell morphology, invasiveness, mitotic activity, and stromal reaction. 3,10 Both grading systems correlate with the survival rate of canine patients with MCTs and histologic grade is the most important factor in determining the staging tests and adjunctive therapy that will be recommended for a dog with a cutaneous MCT. 9,13 Because of the importance of histologic grade in prognosis and decision making in the therapeutic management of dogs with MCTs, it is essential that veterinarians understand the variability among pathologists in assigning grades to MCTs. In a previous study, it was demonstrated that there was significant variation in the histologic grades assigned to the same 60 canine cutaneous MCTs by 10 veterinary pathologists at 1 institution. 8 Because variation in histologic grading was significantly associated with the use of different references describing grading systems, it was hypothesized that if all pathologists utilized the same reference for grading, there would be improved agreement in the grades as- signed to canine cutaneous MCTs. The objective of this study was to determine whether variation among veterinary pathologists in the histologic grading of canine cutaneous MCTs could be eliminated by uniform use of a single grading scheme.Ten veterinary pathologists independently graded the same 60 canine cutaneous MCTs as grade I, II, or III using the Patnaik classifications (Table 1). 10 These were the same 10 veterinary pathologists who participated in the previous study to evaluate variation among pathologists in histologic grading of canine cutaneous MCTs. 8 Four of these pathologists were from the University of Georgia College of Veterinary Medicine (UGA-CVM) Department of Pathology, 5 were from...

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Medical records of 42 cats treated with mandibulectomy for oral neoplasia at eight institutions were reviewed to determine morbidity, progression-free interval, and survival time. Progression-free and survival rates at 1 and 2 years were 56% and 49%, and 60% and 57%, respectively. Cats with squamous cell carcinoma had significantly shorter survival than cats with fibrosarcoma or osteosarcoma. Seventy-two percent of cats were dysphagic or inappetent immediately postoperatively, and 12% never regained the ability to eat. Despite acute morbidity in 98% and long-term morbidity in 76% of cats, 83% of the 30 owners providing information were satisfied with the outcome of mandibulectomy.

The medical records of 24 dogs with histologically confirmed mast cell tumors (MCT) of the muzzle were retrospectively evaluated to determine their biologic behavior and prognostic factors. Information on signalment, tumor grade and stage, treatment methods, and pattern of and time to failure and death was obtained from the medical record. Twenty-three dogs were treated with combinations of radiotherapy, surgery, and chemotherapy; 1 dog received no treatment. There were 2 Grade I, 15 Grade II, and 7 Grade III tumors. Tumors were stage 0 (n ϭ 8), stage 1 (5), stage 2 (6), stage 3 (4), and stage 4 (1). Mean and median survival times of treated dogs were 36 and 30 months, respectively. Prognostic factors affecting survival time included tumor grade and presence of metastasis at diagnosis. Dogs with Grade I and II tumors survived longer than dogs with Grade III tumors. Variables, including sex, age, gross versus microscopic disease, and treatment type were not found to affect survival. Local control rate was 75% at 1 year and 50% at 3 years. Tumor grade was the only variable found to affect local control. Dogs with Grade I tumors had longer disease-free intervals than those with Grade II tumors, and dogs with Grade II tumors had longer disease-free intervals than dogs with Grade III tumors. Eight of 9 dogs dying of MCT had local or regional disease progression. Muzzle MCT are biologically aggressive tumors with higher regional metastatic rates than previously reported for MCT in other sites.