Hemorrhagic cyst vs. hemorrhagic renal cell carcinoma?

[DarBug]

I had a CT Scan, without contrast, done on an emergency basis 1.5 years ago.  The results showed a lot of free air, which was later determined to be due to a vaginal cuff tear.  Through a worker's comp. claim, I was supplied a copy of all of my medical records.  The CT Scan from 1.5 years ago showed a high density lesion on the lower pole of my left kidney.  The radiologist suggested further testing (CT w/ contrast).  None of the doctors ever mentioned this to me at the time the scan was taken.  I brought it to my primary care doctor, and he referred me for a CT Scan with and without contrast.  The results are as follows:  Icm high attenuation lesion in the inferior aspect of the left kidney.  The size of the lesion makes it difficult to evaluate for enhancement, but the lesion measures approximately 78 HU in density precontrast and 94 HU in density postcontrast.  This lesion does not represent a simple cyst.  Differential diagnosis would include hemorrhagic cyst versus hemorrhagic renal cell carcinoma.
My question is, are there any further radiologic tests that can be performed that would further differentiate between the two possible diagnoses?  What are the odds that a 1 cm lesion would turn out to be renal cell carcinoma?