Extrarenal renal cell carcinoma arising in the kidney proximity but without an identifiable renal primary - an intriguing dilemma: report of three cases and review of the literature

Aim To raise awareness of the existence of extrarenal renal cell carcinoma (RCC). Methods and results We report three patients with extrarenal RCC found in the renal proximity, but unattached to the kidney. None had a history of RCC or an identifiable primary renal neoplasm at the time of the diagnosis and on follow-up. The patients included two males and one female aged 57, 77, and 63 years, respectively. One carcinoma was found in the perirenal tissue adjacent to the adrenal, one involved the adrenal gland, and one was a retroperitoneal mass found within the lymph nodes. Two extrarenal RCCs represented clear-cell RCCs and one was an unclassifiable RCC. No patient had evidence of metastases at presentation and disease progression during the follow-up. This report adds to the literature on this unusual clinical scenario and further supports the concept of extrarenal RCC, which is not a well-recognized clinical phenomenon. We also reviewed other similar reports documenting the absence of identifiable renal primaries in the setting of either disseminated metastatic disease or isolated distant metastases of presumed renal origin. Similarly, some carcinomas of apparent renal derivation have been also identified during a work-up of metastatic carcinomas of unknown primary. Conclusions There should be an awareness of this unusual and intriguing clinical scenario that currently lacks a definitive explanation and standardized therapy strategies. Establishing a correct diagnosis may allow treatment with specific targeted therapies in selected clinical cases.