Table 2.

Frequency with which binary features were present in focal type 1, focal type 2 and infiltrative papillary renal cell carcinoma (pRCC), with P value obtained from univariate generalised estimating equations analysis for comparison between categories of pRCC

Feature	Focal type 1 pRCCa	Focal type 2 pRCCa	P (focal type 1 vs. focal type 2)	Infiltrative pRCCa	P (infiltrative vs. all focal)
Metastatic diseaseb	3.7 (2/54)	7.5 (3/40)	0.648	75.0 (6/8)	<0.001
Central location	4.6 (3/65)	5.6 (3/54)	1.0	88.9 (8/9)	<0.001
Poorly encapsulated	0 (0/65)	3.7 (2/54)	0.204	100 (9/9)	<0.001
Renal vein thrombus	0 (0/65)	0 (0/54)	1.0	88.9 (8/9)	<0.001
Irregular margins	21.5 (14/65)	35.2 (19/54)	0.089	100 (9/9)	<0.001
Perirenal invasion	6.2 (4/65)	3.7 (2/54)	0.688	55.6 (5/9)	<0.001
Retroperitoneal collaterals	30.8 (20/65)	22.2 (12/54)	0.309	77.8 (7/9)	0.007
Homogeneous enhancement	46.2 (30/65)	42.6 (23/54)	0.715	11.1 (1/9)	0.084
Microscopic fatc	7.9 (5/63)	3.8 (2/53)	0.451	22.2 (2/9)	0.095
Homogeneous T2 signal intensity	35.4 (23/65)	22.2 (12/54)	0.157	11.1 (1/9)	0.264
Haemosiderinc	27.0 (17/63)	50.9 (27/53)	0.056	22.2 (2/9)	0.358
Necrosis	32.3 (21/65)	25.9 (14/54)	0.448	55.6 (5/9)	0.117
Haemorrhage	41.5 (27/65)	70.4 (38/54)	0.004	22.2 (2/9)	0.082
High grade (most common)	1.5 (1/65)	38.9 (21/54)	<0.001	44.4 (4/9)	0.077
High grade (highest)	38.5 (25/65)	88.9 (48/54)	<0.001	88.9 (8/9)	0.134
Stage T2/T3	11.1 (7/63)	28.0 (14/50)	0.022	87.5 (7/8)	<0.001

Data listed in bold are statistically significant at P<0.05. Features not recorded in binary fashion (T2 signal intensity, enhancement in nephron-graphic phase, and cystic component) are not included in the table but did not show significant differences for any comparisons (P>0.05)

^aData are percentages, with raw numbers in parentheses

^bNot included in patients for whom presence or absence of metastatic disease could not be determined

^cNot evaluated in three lesions imaged at 3.0 T with in-phase echo acquired before the opposed-phase echo