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Renal Cortical Adenoma
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- Many have disputed this entity, as metastases have been recorded from many small (<3.0 cm) renal cortical lesions (i.e., all cancers must start out small...).
- Nevertheless, many have noted the occurrence of small lesions that most often occur in the cortex of kidneys “scarred” by pyelonephritis or renal vascular disease. Generally these lesions come to light at autopsy or at the time of nephrectomy for unrelated causes.
- Gross features: assuming that -- at least in this case -- “size matters”, the best candidates for the diagnosis of renal cortical adenoma are less than 1.0 cm, well demarcated, and generally subcapsular. Cut surface is usually yellow or gray.
- Histologic features:
- bland, closely-packed cells with eosinophilic cytoplasm forming tubules and papillary structures.
- nuclei are uniform and mitoses are rare or absent
- the interface with the normal kidney should be sharp, without "infiltrative" borders or stromal reaction/ inflammation.
Caveat: Any clear cell neoplasm in the cortex, no matter how small, should be considered a carcinoma.
- Prognosis: Again, assuming that a certain proportion of these may represent incipient neoplasia, it is impossible to definitively predict the biologic behavior of these lesions; however, if they are truly adenomas they should not metastasize or invade.
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