A rare case of renal cystic oncocytoma: Case report

Abstract

Renal oncocytomas are relatively benign renal tumours, accounting for approximately 5 % of primary adult epithelial kidney neoplasms that are surgically removed.

The Bosniak classification is used to assist in estimating the probability of cancer and make recommendations for therapy or subsequent studies. We report a 52-year-old male who presented with a left renal cyst with an enhancing nodular component which showed interval increase in the size after one year (Bosniak IV). Given the diagnosis of Bosniak IV, a radical nephrectomy was performed. The diagnosis of renal oncocytoma was confirmed post-operatively through histopathological examination.

1 Introduction

Renal cysts are spherical, thin-walled, variable-sized distensions filled with clear fluid, and mostly form in the cortical or medullary renal tubules. Both benign and malignant tumours can present as renal cysts. Simple cysts, which have a thin wall enclosing a fluid that resembles water, are the most frequent kidney masses, and they are typically asymptomatic. Complex cysts have a solid component inside and are either septated or enhanced on imaging. They could show symptoms including pain, fever, and haematuria and increase the possibility of malignancy.

Renal oncocytomas are mostly slowly growing benign kidney tumours. The primary clinical significance of this lesion is the challenge of preoperatively differentiating it from renal cell carcinomas due to their often identical epidemiology, presentation, imaging, and even histology. We report a case of renal cystic oncocytoma that manifested as completely endophytic Bosniak IV cystic mass located in the lower half of the kidney with features suspicious of renal cell carcinoma. A post-operative histopathological examination confirmed the diagnosis.

2 Clinical presentation

A 52-year-old male patient presented to the emergency department complaining of bilateral loin pain and dysuria. The patient was vitally stable and routine laboratory tests including renal functions were within normal limits. An abdominal ultrasound revealed a well-defined endophytic cystic lesion in the midpole of the left kidney, containing a solid isoechoic nodule with internal vascularity, as observed on Doppler imaging ( Fig. 1 ).

CT abdomen and pelvis with excretory phase was done which showed an endophytic cystic mass lesion with internal solid component in the mid pole of left kidney. The internal solid component showed post contrast enhancement on excretory phase. There was a non-obstructive calculus in the lower pole of left kidney ( Fig. 2 ).

Because of the lesion’s small size, the patient was treated symptomatically with regular outpatient follow up.

The patient came to the ED after one year with complaints of left loin pain. He was vitally stable, and laboratory results were unremarkable. CT abdomen and pelvis with excretory phase demonstrated interval increase in the size of endophytic cyst mass with enhancing intralesional solid component in the interpole of left kidney. The non-obstructive calculus in the lower pole of left kidney was again noted ( Fig. 3 ).