Which statement about renal cyst septations is true?

Which statement about renal cyst septations is true?

• A. Septations Less Than 1 Mm Thick Are Mostly Benign
• B. Septations Greater Than 2 Mm Thick Are Benign
• C. All Septated Cysts Are Malignant
• D. Septations Equal to 5 Mm Thick Indicate a Bosniak 4 Cyst

Answer: (A)

The main idea being tested is how the thickness of internal septations within a renal cyst relates to its Bosniak category and cancer risk. Thin septations, especially those less than 1 mm, are characteristic of simple or minimally complex cysts (Bosniak II) and are associated with a very low risk of malignancy. That’s why the statement about septations under 1 mm being mostly benign is the best choice. As septations become thicker, the lesion becomes more complex. Septa thicker than about 1–2 mm raise suspicion for a more advanced Bosniak category (IIF or III) and may require closer imaging evaluation or follow-up. Thick septations alone do not make a cyst malignant. The definitive Malignancy indicator is an enhancing solid component on CT or MRI, which would push toward Bosniak IV. The other statements aren’t accurate because thick septa are not inherently benign, not all septated cysts are malignant, and thick septa alone do not define a Bosniak IV cyst (which requires an enhancing solid portion).

The main idea being tested is how the thickness of internal septations within a renal cyst relates to its Bosniak category and cancer risk. Thin septations, especially those less than 1 mm, are characteristic of simple or minimally complex cysts (Bosniak II) and are associated with a very low risk of malignancy. That’s why the statement about septations under 1 mm being mostly benign is the best choice.

As septations become thicker, the lesion becomes more complex. Septa thicker than about 1–2 mm raise suspicion for a more advanced Bosniak category (IIF or III) and may require closer imaging evaluation or follow-up. Thick septations alone do not make a cyst malignant. The definitive Malignancy indicator is an enhancing solid component on CT or MRI, which would push toward Bosniak IV.

The other statements aren’t accurate because thick septa are not inherently benign, not all septated cysts are malignant, and thick septa alone do not define a Bosniak IV cyst (which requires an enhancing solid portion).