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Urology/Complex Kidney cyst


I was diagnosed with a complex kidney cyst, rated a Bosniak 3
Its 4.2 cm,upper pole right kidney,demonstrates washout on delayed imaging,demonstrates a septation as well which enhances slightly.

My doctor wants me to go for a biopsy before seeing a urologist.

My questions:
Since its a Bosniak 3 , will i automatically have to have surgery anyway ?
What are my chances that its NOT cancer? i know they say 50 % but I'm asking ,from your experience how many are and how many aren't?

I don't want to put myself thru a biopsy if I'll need surgery anyway.
Doesn't it mean if it enhances,it has a blood supply which is cancer?

Thanks in advance for your assistance


Bosniak 3 classification for cysts is suggestive of a possible cystic type tumor.  I would certainly not recommend a biopsy without talking to a urologist since there is a good chance a surgery will be recommended without it.

My personal experience suggests that slightly less than 50% are ultimately found to be cancers which is roughly what the reported studies suggest.

Bosniak Category III: Malignant risk 40-60%; surgical excision recommended
More complicated
uniform wall thickening/nodularity
thick/irregular calcification
thick septa
enhances with contrast

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QUESTION: Thanks for the fast and informative response!

Couple other questions/concerns i have if you'd be so kind,

If it is Cancer, how long would i be able to go before having surgery?

Would a biopsy possibly give a false negative?

And would a biopsy possibly disturb this thing to where it metastasizes?

Thanks again


How long you are able to go before having surgery depends on the nature and the degree of the cancer which is unknown.  You should reasonably have it taken care of one way or the other within a few months.

If the lesion is amenable to cryotherapy, then the biopsy can be done at that time.  If not, then a surgical excision might be reasonable and the biopsy is not needed.

Biopsies tend not to give false negatives, but only if you actually biopsy the right place.  If your biopsy is from a normal area of the cystic lesion, then you'll get a false negative reading.  It can also be difficult to get tissue from exactly the right spot which is why other treatment is recommeded.

A biopsy is not likely to cause metastases but that doesn't mean it's impossible.


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Stephen W. Leslie, MD


Questions concerning erectile dysfunction, kidney stones and prostate disorders including prostate cancer. I have a special interest in kidney stone disease prevention.


Full time practicing urologist with 30 years experience. Associate Professor of Surgery and Chief of Urology at Creighton University Medical Center. Editor in Chief of eMedicine Urology internet textbook. Author of only NIH approved book written for patients by a urologist on the subject of kidney stones "The Kidney Stones Handbook". Inventor of the "Parachute" and "Escape" kidney stone baskets and the "Calculus" stone prevention analysis computer program.

American Urological Association, Ohio State Medical Association, Sexual Medicine Society

Men's Health, Journal of Urology, Urology, Healthwatch Magazine, Emergency Medicine Monthly, eMedicine, "The Kidney Stones Handbook", and numerous articles in various newspapers. He is also the editor of the Urology Board Review by McGraw-Hill used by urologists to study for their Board Certification Examinations.

Graduate of New York Medical College with residencies completed at Metropolitan Hospital New York, Albany Medical Center and University of Wisconsin-Madison.

Awards and Honors
Thirlby Award of the American Urological Association. Rated as one the country's Best Urologists by the Independent Consumer's Research Institute

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