A renal adenoma is a benign renal neoplasm. It is traditionally classified into three distinct types (renal papillary adenoma, renal tubular adenoma, and alveolar renal adenoma). The papillary type is the commonest variant with an estimated prevalence of 40 % in patients older than 70 years of age.
Such lesions are histologically indistinguishable from larger carcinomas more commonly encountered in the kidneys, and they often have histologic grades indicating a definite potential for malignant behavior. Accordingly, most investigators believe that these lesions should be regarded as carcinomas in an early stage of evolution and should not be classified as adenomas.
On CT, these small renal tumors are usually well defined and homogeneous in appearance. Less commonly, they show marginal irregularity, heterogeneity, or central calcification, findings that may suggest pathologically high-grade tumors. These lesions are best managed with partial nephrectomy, provided that the...