Management of 1.2 cm Right Renal Cortical Cyst
A simple renal cortical cyst of 1.2 cm requires no intervention or follow-up imaging in asymptomatic patients, as it is benign and carries essentially zero malignancy risk. 1
Diagnostic Confirmation
High-quality cross-sectional imaging (CT or MRI) should confirm the cyst meets criteria for a simple cyst: anechoic/hypodense, smooth thin wall, no septations, no solid components, no enhancement, and sharp margins with the renal parenchyma 1
Simple cysts measuring <20 HU on unenhanced CT are definitively benign 2
Be aware that cysts ≤1.0 cm may show artifactual pseudoenhancement up to 11 HU on contrast-enhanced CT due to partial volume averaging—this does not indicate malignancy 3
Management Recommendations
No further management is required for this lesion. The evidence strongly supports observation without intervention:
Simple cysts ≤3 cm in premenopausal women are considered physiologic and require no follow-up 1
In a study of 72,093 women, zero simple cysts were diagnosed as cancer in women <50 years, and only 1 of 2,349 simple cysts proved malignant in women >50 years at 3-year follow-up 1
The malignancy risk for true simple cysts is approximately 0.5% in premenopausal women and 1.5% in postmenopausal women, though these figures likely overestimate risk as they included only surgically removed lesions 1
Key Distinctions from Solid Renal Masses
This management differs entirely from solid renal masses, where active surveillance protocols and size-based interventions apply:
The AUA guidelines for active surveillance of masses <2 cm apply only to solid renal masses, not simple cysts 4, 2
Solid masses require repeat imaging at 3-6 month intervals to assess growth rate 4
Simple cysts require no such surveillance 1
Critical Pitfalls to Avoid
Do not confuse simple cysts with complex cystic lesions (Bosniak III/IV), which require entirely different management including potential surgical intervention 1, 5, 6
Do not biopsy simple cysts—biopsy is indicated only for solid masses prior to thermal ablation or when risk-benefit analysis is equivocal 4
Ensure the lesion truly meets simple cyst criteria with proper imaging technique, as misclassification could lead to inappropriate surveillance or intervention 6
If the cyst becomes symptomatic (pain, infection, hemorrhage, or causes hydronephrosis), then intervention with percutaneous aspiration with sclerotherapy or laparoscopic decortication may be considered 5