Pathological nature of renal tumors - does size matter?

Introduction: We examined the relationship between the size and nature of renal masses in term of malignant potential, histological grading, pathological staging and presence of necrosis and sarcomatoid changes.

Materials and Methods: Retrospectively, we reviewed 323 consecutive nephrectomies between 2000 and 2010. Final pathology was correlated with tumour size. The renal tumours were stratified into three groups according to the largest diameter, defined as 4 cm or smaller, greater than 4 cm to 7 cm, and greater than 7 cm. We recorded the proportion of benign tumours, tumour grade and stage, presence of necrosis and sarcomatoid change.

Results: Small renal masses ≤4 cm (SRMs) were more likely to be localised to the kidney (90%) and of lower histological grade (75%). The proportion of benign tumours in SRMs (15%) was higher than other two groups with the majority of benign tumours being oncocytomas. There was a statistically significant trend with greater necrosis and sarcomatoid change for the large size group.

Conclusions: SRMs are likely to be low grade and organ confined with little or no adverse pathological features. There is increased likelihood of benignity in SRTs with the majority of benign tumours being oncocytomas.