Differences in peritumoral pseudocapsule characteristics according to clinicopathological factors in clinical T1a renal tumors.

OBJECTIVES To evaluate the status of peritumoral pseudocapsules in renal tumors and the effects of clinicopathological factors on their formation. METHODS From January 2011 to December 2012, 258 patients with solitary clinical stage T1a renal tumors who underwent partial nephrectomy were analyzed. Status of pseudocapsule was re-evaluated by a pathologist. RESULTS The mean long diameter (± SD) of the tumor and the width of the safety margin were 2.17 (± 0.94) cm and 3.2 (± 2.4) mm, respectively. A complete pseudocapsule was identified in 152 (58.9%) tumors, an incomplete pseudocapsule was identified in 69 (26.7%) tumors, and no pseudocapsule was identified in 37 (14.3%) tumors. Out of 152 tumors with complete pseudocapsules, 45 (29.6%) were confirmed to directly invade the renal parenchyma. In a multivariable analysis, age (odds ratio [OR], 1.045; 95% confidence interval [CI], 1.021-1.070, P < 0.001) and histologic subtype (chromophobe type: OR, 19.455; 95% CI, 4.233-89.471, P < 0.001; oncocytoma: OR, 11.307; 95% CI, 1.357-94.198, P = 0.025) were significant factors for an incomplete or absent pseudocapsule. CONCLUSIONS Peritumoral pseudocapsules are absent or incomplete in a significant portion of renal tumors. Old age as well as chromophobe and oncocytoma histologic subtypes were significant risk factors for an incomplete or absent peritumoral pseudocapsule.