The impact of tumour location on the histological subtype of renal cortical tumours

Abstract

To determine whether the location of renal cortical tumours (RCTs) is a possible factor affecting tumour behaviour, by investigating whether exophytic vs a central location is associated with a difference in histological subtype distribution, as recognized prognostic factors for RCTs include size, stage, grade, and histological subtype. Between 1 January 1996 and 1 June 2003, we evaluated 485 consecutive RCTs in 469 patients who had renal imaging studies and underwent either partial or radical nephrectomy at our institution. A radiologist and a urologist independently reviewed the imaging studies of all patients to determine exophytic vs central location. An exophytic lesion was defined as one that clearly both pushed out the renal contour and did not extend into the collecting system, hilum, or renal sinus. A lesion that did not meet these criteria was defined as a central lesion. Logistic regression analysis was used to determine if either type of lesion had a greater representation of any histological subtype. A two-tailed P < or = 0.05 was considered to indicate significance. Of the 485 RCTs, 171 (35%) were exophytic and 314 (65%) were central, while 308 (64%) were clear cell and 177 (36%) were non-clear cell tumour histology. Of the exophytic lesions, 52.0% were clear cell, while 69.7% of central lesions were clear cell (P < 0.001). Conversely, 71.1% of clear cell tumours were central, while 53.7% of non-clear cell tumours were central (P = 0.003). After controlling for size and stage, tumour location remained associated with histological subtype (P = 0.003). Exophytic lesions are significantly more likely than central lesions to be non-clear cell tumours, and clear cell tumours are significantly more likely than non-clear cell tumours to be central. As studies indicate that the clear cell histological subtype portends a worse prognosis than the non-clear cell subtype, our results imply that tumour location affects the prognosis in RCTs, with exophytic lesions having a better prognosis than central lesions. This result may have important implications for physicians and patients when planning partial vs radical nephrectomy by either open or minimally invasive techniques.