Reviewer response for version 1
The authors report a heterotopic adrenal oncocytoma in a 65 year-old lady with essential hypertension. 
A routine ultrasound detected a 5 cm adrenal mass, however, MRI showed a 4.8 x 4.8 x 3.3 cm mixed intensity upper polar renal mass. 
Features were not suggestive of a malignant tumour. 
Urinary and blood work up excluded a functioning adrenal adenoma. 
The oncocytoma was removed retroperitoneoscopically with the zero-ischemia technique.
It is a well written report, however, I have the following observations on the current submission:
- The sequence of the work up is not clear: was the MRI done first; or were urinary catecholamines and metanephrines, aldosterone-renin ratio and serum cortisol determined first? 
In the latter case, why was a pheochromocytoma suspected when neither the clinical manifestations nor imaging (MR) suggested a pheochromocytoma?
- The authors have rightly noted that the imaging characteristics of benign and malignant oncocytoma are not clearly described in the current literature - they were entertaining a diagnosis of an RCC pre-operative. 
Did the authors consider doing a biopsy prior to surgical intervention? 
It would be pertinent to mention indications for biopsy in such a situation, and discuss its merits and demerits.
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