Should A Persistent Cyst Like Mass At The Left Kidney Be Seriously Diagnosed And Treated

Question : hi , 6 years ago (2012) i found a mass on left kidney during an ultra sound , the doctors said that its a simple cyst but then later and after 2 years 2014 and during MRI on something else the doctor was concerned about the mass and asked for follow up with urologist as this mass doesn%E2%80%99t look ok and might be a tumor , in 2015 i did CT and the urologist said it looks really strange but its a cyst bosniak 2 and I should forget about it , the size of this mass is around 3 x 4 cm and it change slightly during the last 6 years, last week i was doing an ultrasound on gallbladder to remove it and again another doctor said that this mass no way is a cyst however the size still the same as at 2015, now my question is should i be concerned ? Since i did CT 3 years ago can this complex cyst turn into tumor. Or if its once a cyst always will remain a cyst

also all my blood and urine tests are ok

hi , thank you for your reply , my question now is can this mass be a tumor ? despite the size remain almost the same for 6 years or tumors grow