All of the following statements about CT scan features of adrenal adenoma are true, EXCEPT:
**Core Concept**
Adrenal adenomas are typically benign tumors of the adrenal gland, and their characteristics on computed tomography (CT) scans can help differentiate them from malignant lesions. The CT scan features of adrenal adenomas often include a well-defined border, homogenous density, and a size less than 4 cm.
**Why the Correct Answer is Right**
Adrenal adenomas typically exhibit a **low attenuation value** on non-contrast CT scans, often less than 10 Hounsfield Units (HU), which is due to the high water content within the tumor. This characteristic helps in distinguishing adenomas from non-adenomas. Additionally, adrenal adenomas usually show **homogeneous enhancement** on contrast-enhanced CT scans, with a **washout pattern** of more than 60% at 15 minutes, indicating their benign nature.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while some adrenal adenomas may exhibit a **high attenuation value** on non-contrast CT scans (more than 10 HU), this is not a defining characteristic of the majority of adenomas.
**Option B:** Incorrect because **heterogeneous enhancement** on contrast-enhanced CT scans can be seen in both benign and malignant adrenal lesions, making it an unreliable feature for differentiating adenomas from non-adenomas.
**Option C:** Incorrect because **washout pattern** of less than 60% at 15 minutes is more indicative of non-adenomas, such as metastases or pheochromocytomas.
**Clinical Pearl / High-Yield Fact**
When evaluating adrenal lesions on CT scans, remember that a **low attenuation value** and **homogeneous enhancement** with a **washout pattern** of more than 60% at 15 minutes are key features of benign adrenal adenomas.
**Correct Answer:** D