Abstract. In this study, age, sex, recurrence, metastasis, death rate, and histologic patterns were in agreement with those of previous reports on canine mast cell tumors. Histologic grading, mitotic index, chromosome nucleolar organizer regions stained with silver (AgNORs), and anti-proliferating cell nuclear antigen (PCNA) were evaluated as indicators of prognosis. Histologic grading, AgNORs estimated in 100 cells, and PCNAlabeled fraction estimated in five high power fields (HPFs) were significantly different between recurring and nonrecurring tumors. Those prognostic factors were also significantly different between tumors that metastasized and those that did not. The survival time was lower in dogs with mast cell tumors with histologic grade 3 (Patnaik's), AgNOR counts higher than 2.25, and PCNA count in five HPFs higher than 261. The significance of these factors as markers for prognosis determined by logistic regression analysis differed with the time period considered. By combining the three most significant prognostic factors in a prognostic index, three models were obtained to determine the probability of nonrecurrence at 3, 6, and 9 months after surgery. The models were accurate in the prediction of the outcome of up to 80% of mast cell tumors. The use of these models provides a less subjective means of prognosticating mast cell tumors than the use of any one component alone.

Abstract. Idiopathic cutaneous and renal glomerular vasculopathy (CRGV) (Alabama rot) is a potentially fatal disease of unknown etiology that affects the skin and kidneys of racing-and training-age Greyhounds. Ultrastructural examinations were performed on two healthy control Greyhounds and 1 2 Greyhounds diagnosed with CRGV based on the presence of characteristic, well-demarcated cutaneous ulcers of the extremities (1 2/ 12), thrombocytopenia (<200,000 plateletddl) (1 2/12), and acute renal insufficiency (BUN > 40 mg/dl, serum creatinine > 2.0 mg/dl) (7/ 12). Early glomerular ultrastructural changes included endothelial swelling, detachment, and necrosis; membranous whorl formation; and platelet adhesion and aggregation. Some capillaries were occluded with aggregated platelets, cellular fragments, and fibrin. Later changes included narrowing of capillary lumina and thickening of glomerular capillary walls by subendothelial accumulation of flocculent, amorphous, variable electron-dense material and occasionally erythrocytes, cellular processes, and fibrin. Glomerular endothelial cells were increased in number and plump, with villouslike cytoplasmic projections. Mesangial cell cytoplasmic processes occasionally were interposed between the endothelium and the basement membrane. No etiologic agents or electron-dense deposits typical of immune complexes were observed. Although the specific etiology was not determined, the ultrastructural changes suggest that glomerular endothelial damage is an important early event in the pathogenesis of CRGV.

Abstract. Twelve histochemical methods; affinity staining with avidin peroxidase, wheat germ agglutinin, and concavalin-A agglutinin; and an immunohistochemical stain with Kpl (CD68) antibody were compared for their relative effectiveness in staining canine mast cell tumors. Stains were compared in 28 mast cell tumors and 19 histiocytomas. The effectiveness of the histochemical methods and the lectins decreased as the mast cells became less differentiated. None of the staining methods were positive on histiocytomas. Periodic acidSchiff (PAS) gave positive results in a few cases of mast cell tumors where other histochemical stains were negative. Although avidin peroxidase and Kpl antibody stained more mast cell tumors than any other method, they did not differ significantly from Luna's method, toluidine blue pH 0.5, toluidine blue pH 4.5, alcian blue pH 2.5, safranin O, Unna's method, and Giemsa. No stain was ideal for the diagnosis of canine mast cell tumors; however, this study suggests that the use of avidin peroxidase, Kpl antibody, and PAS may give additional information for individual poorly differentiated tumors without substantial increase in time or cost.

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Gratitude is extended to Dr. 3ames Cook and Dr. Albert Strafuss for serving on my advisory committee and for their guidance through my program. Special thanks is offered to Dr. Stanley M. Dennis for making possible my graduate program. I also want to thank Dr. James Higgins for assistance in the statistical analysis of the data, Frank Leatherman for the histotechnic procedures, and Duane Kerr for the photographic material. My thanks to my parents for the education they gave me, and to my parents-in-law for they support and encouragement. Special thanks to my husband for his help, encouragement, and love.