Table 4. The risk factors influencing canine mammary gland tumor (CMT) cases compared with other tumor cases (N = 1, 391).

Factors	CMT cases		Other tumor cases		Odds ratio	95% CI	P-value
	n	%	n	%
1. Sex (n = 1,356)
Female (n = 825)	364	97.6	461	46.9	45.8	23.9–86.0	<0.0001*
Male (n = 531)	9	2.4	522	53.1	1.0
Total	373	100.0	983	100.0
2. Age (n = 1,316)
≤8 years (n = 481)	106	28.4	375	39.8	1.0
>8 years (n = 835)	267	71.6	568	60.2	1.76	1.27–2.2	0.0001*
Total	373	100.0	943	100.0
3. Breed (n = 1,391)
Purebred (n = 753)	214	57.4	539	52.9	1.2	0.9–1.5	0.15
Mixed breed (n = 638)	159	42.6	479	47.1	1.0
Total	373	100.0	1,018	100.0

Notes.

^*Significant difference was accepted at P-value <0.05.

^**The retrospective data on sex was not recorded in 35 non-CMT cases.

^***The retrospective data on age was not recorded in 75 non-CMT cases.