I had bladder cancer 10 yrs ago. simple cyst in left kidney was 3mm, now 8mm and read as complex. what is the probability of malignancy?

Possible.: Difficult to give you probability statistics in this setting, but any complex cyst requires close monitoring. With your history of bladder cancer, though, i encourage you to follow up with your urologist for his/her opinion. Malignancy unfortunately is not out of the question, but would be much easier to manage sooner rather than waiting until later. Best of luck to you.

Renal cyst: Need to know bozniak classification of your cyst; 1 is simple 2-5 are complex, 3-5 are higher cancer risk and need removal. Grade 2 need regular monitoring.