174 The Lymphocyte and Lymphocytic Tissue 



located in the kidneys. These lesions (Fig. 13-9) often result in death due 

 to renal failure before any significant gross lesions are evident elsewhere 

 in the body. In a nearly equal group (18 per cent) the anterior mediastinum 

 (and presumably thymus) is filled with tumor (Fig. 13-10), thereby making 

 the initial signs referable to respiratory difficulty. This is a feature that 

 also occurs in certain strains of mice affected with malignant lymphoma. 



3 4 5 



7 8 9 10 11 12 13 14 15 16 1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 16 17 18 



AGE IN YEARS AGE IN YEARS 



Fig. 13-13. Age distribution of malignant lymphoma in 117 clogs and ( J8 cats. 



The liver is primarily affected in 17 per cent of the feline cases, and the 

 presenting signs are referable to liver failure. This infiltration may be 

 diffuse or nodular. Single nodules of malignant lymphoma in the small 

 intestine or mesenteric lymph nodes are found in about 15 per cent of the 

 cases (Fig. 13-11). Palpable abdominal masses and intestinal obstruction are 

 therefore fairly frequent clinical findings. Leukemic blood picture is en- 

 countered in about 10 per cent of the cases in cats. 



The incidence of malignant lymphoma in cats appears to be nearly twice 

 that of dogs (Fig. 13-12). The average rate per 1,000 admissions during the 

 years 1954 through 1958 was about 5.5. The records prior to these years 

 probably are incomplete. The age of affected cats ranges from a few months 

 to seventeen years (Fig. 13-13). A significantly greater number of young 

 animals of this species are affected in comparison with the dog. 



