1 Institute of Urology, University Medical School Pécs 2 Nephrological Center, Second Department of Medicine, University Medical School Pécs, Hungary
Sir,
Renal oncocytoma accounts for approximately 5% of renal parenchymal tumours [1], but bilateral, multifocal renal oncocytoma is rare. In recent years renal oncocytoma has been more frequently identified. Possible explanations include more frequent screening in patients with non-specific symptoms causing a spurious increase in incidence [2]. Renal oncocytoma represents a highly differentiated eosinophilic granular cell renal parenchymal tumour. It is non-aggressive and has a favourable prognosis [3]. There are sporadic reports on bilateral, multifocal oncocytomas having semi-malignant potential, i.e. locally invasive growth, and reports on renal oncocytoma plus renal cell carcinoma as simultaneous, but separate, lesions [4,5]. Usually these patients are managed by enucleation of the large tumours. Overall prognosis is regarded as acceptable, considering the generally benign nature of these neoplasms [6]. We report a patient with bilateral, multifocal renal oncocytomatosis, who had rapidly progressive renal failure. Bilateral nephrectomy was performed to prevent a potential extrarenal progression.
Case.
In October 1994, a woman of 27 was examined because of hypertension. Ultrasonography showed a smaller kidney than normal on the right side, and a tumorous alteration of 2 cm on the left side. Radionuclid renography showed a function reduced by 50% on the right side. Computer tomography (CT) could not determine the feature of the process. A fine needle biopsy specimen suggested the possibility of a malignant process. In the course of open surgery three further tumours of 0.5 cm were found on the surface of the kidney. The four observed lesions were resected. In frozen sections all tumours were found to be oncocytomas. A CT check-up was performed at 3 months interval. After 6 months lesions had recurred in the left kidney, and several small lesions were found in the right kidney as well. A subsequent CT scan showed that the space occupying lesions had increased in size and number. The patient's renal function had decreased and chronic haemodialysis treatment was planned. In February 1997, the right non-functioning kidney was removed. Four weeks later left nephrectomy was performed as well. Histology showed numerous oncocytomas, 14 cm in diameter, with the characteristic histological features. They did not infiltrate the capsule. Since then the patient has been on chronic dialysis and checked regularly. No tumour recurrence was detected and the patient works in her original office job.
Comment.
So far cases of bilateral oncocytomatosis with rapidly progressing renal failure necessitating renal replacement therapy have not been published. Choi and associates noted arterial hypertension in eight of 44 patients (16%), in another review, 36% were hypertensive [1,7]. In our case, the only presenting feature was hypertension. Subsequently she developed reduced renal function. Unfortunately, there is no reliable preoperative diagnostic procedure distinguishing oncocytoma from clear cell renal carcinoma. Even needle biopsy or frozen section do not exclude renal carcinoma with focal oncocytic differentiation. The excellent prognosis of oncocytomas is an argument to adopt nephron sparing surgery [1]. The histological analysis of our case also supports the strategy of nephron sparing surgery, but rapidly progressive renal failure resulting from destruction of renal parenchyma prompted us to proceed to bilateral nephrectomy. We consider to transplant the patient, but it should be emphasised that oncocytomas have been recently reported in a transplanted patient too [8].
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