Methodologic Approaches to Histologically Distinguishing Vaccine versus Nonvaccine-Associated Sarcomas Using Validated Time and Location Vaccination Histories in Cats

Table 2

Multivariate exact logistic regression analyses of associations between histologic characteristics of vaccine-associated sarcomas occurring within one (case Group 1), two (case Group 2), and three (case Group 3) years of vaccination and occurring at sites typically used for vaccination regardless of vaccine history (case Group 4) and four comparison sarcoma groups varying by location and vaccine history. All models were adjusted for age.

	variables*	Case Group 1^a (𝑛=15)			variables	Case Group 2^b (𝑛=27)			variables	Case Group 3^c (𝑛=34)			variables	Case Group 4^d (𝑛=87)
		OR	95% CI	P value		OR	95% CI	P value		OR	95% CI	P value		OR	95% CI	P value
Control A^1; (𝑛=18)	Mitotic index	0.5	0.2, 1.0	0.053
	Demarcated borders	0.1	0.0, 1.7	0.179
	Differentiation	0.3	0.0, 1.4	0.150
Control B^2; (𝑛=8)	Mitotic index	0.4	0.1, 1.1	0.090	Mitotic index	0.3	0.1, 0.9	0.026
	Nuclear pleomorphism	0.1	0.0, 1.5	0.148	Nuclear pleomorphism	0.2	0.0, 1.3	0.089
					Neutrophils	0.1	0.0, 1.2	0.069
Control C^3; (𝑛=15)									Nuclear pleomorphism	2.5	0.7, 10.1	0.167
Control D^4; (𝑛=35)	Inflammation	4.2	0.9, 42.6	0.081	Location in dermis	0.04	0.0, 0.3	<0.001	Inflammation	2.8	0.9, 10.9	0.088	Inflammation	3.9	1.3, 13.7	0.013
	Multinucleated giant cells	5.7	0.7, 77.1	0.112	Myxomatous stromal components	23.3	2.3, 1322.0	0.002	Location in dermis	0.04	0.0, 0.3	<0.0001	Location in dermis	0.1	0.0, 0.4	<0.0001
	Location in dermis	0.03	0.0, 0.2	<0.0001					Myxomatous stromal component	12.9	1.0.0, 816.6	0.047	Myxomatous stromal component	6.9	1.5, 46.9	0.010
													Multinucleated giant cells	2.6	0.7, 10.7	0.172
													Neutrophils	0.3	0.1, 1.1	0.066
Control E^5; (𝑛=37)	Inflammation	4.5	1.0, 45.9	0.056	Inflammation	2.5	0.7, 10.5	0.187	Inflammation	3.1	1.0, 12.0	0.052	Inflammation	3.0	1.1, 8.6	0.023
	Multinucleated giant cells	6.1	0.8, 82.9	0.094	Location in dermis	0.1	0.0, 0.4	<0.001	Location in dermis	0.04	0.0, 0.3	<0.0001	Location in dermis	0.1	0.0, 0.4	<0.0001
	Location in dermis	0.03	0.0, 0.2	<0.0001	Myxomatous stromal Component	12.9	1.1, 784.1	0.041	Myxomatous stromal component	12.5	1.0, 785.5	0.051	Myxomatous stromal component	6.6	1.5, 40.7	0.009
													Multinucleated giant cells	2.4	0.7, 9.4	0.187

*Variables listed are those found to have a P value ≤ 0.20 after a backward variable selection process starting with a multivariate model containing all predictors exhibiting a P value ≤ 0.20 in the univariate analyses and patient age.
^aCase Group 1: cats with a documented history of vaccination time no less than 30 days to no greater than one year (365 days) injected within one grid on any side of tumor site.
^bCase Group 2: cats with a documented history of vaccination time no less than 30 days to no greater than two years (730 days) injected within one grid on any side of tumor site.
^cCase Group 3: cats with a documented history of vaccination time no less than 30 days to no greater than three years (1095 days) injected within one grid on any side of tumor site.
^dCase Group 4: cats with a documented history of vaccination at sites commonly used for vaccination regardless of vaccine history at tumor site.
¹Control Group A: cats with a documented history of vaccination no less than 365 days injected within one grid on any side of the tumor site.
²Control Group B: cats with a documented history of vaccination no less than 730 days injected within one grid on any side of the tumor site.
³Control Group C: cats whose tumors arose at sites typically used for vaccination and with no history of vaccination at tumor site within the previous three years.
⁴Control Group D: cats whose tumors arose at sites not typically used for vaccination and with verification that they were not previous vaccination sites.
⁵Control Group E: cats whose tumors arose at sites not typically used for vaccination even if no vaccine history was available.