A 58-year-old hypertensive man undergoes axial CT abdomen for unrelated abdominal pain. An incidental mass is noted at the structure marked **B** on the diagram. The lesion measures 3.2 cm, has a triangular shape, and shows unenhanced density of 8 Hounsfield units with 65% absolute washout on delayed imaging. Which of the following is the most appropriate next step in management?

Explanation

## Why "Repeat CT imaging at 6 and 12 months with clinical observation" is right The structure marked **B** is the left adrenal gland, which typically sits superior and medial to the upper pole of the left kidney with a triangular or crescent shape on axial CT. This patient has an adrenal incidentaloma with benign imaging features: unenhanced density of 8 HU (lipid-rich, <10 HU = benign adenoma), 65% absolute washout (>60% = adenoma), and size <4 cm. Per Harrison 21e Ch 386 and Gray's Anatomy 42e Ch 73, the workup for adrenal incidentaloma requires assessment of functionality (hormone excess) AND malignancy risk. However, this mass has imaging features strongly suggestive of a benign lipid-rich adenoma with no imaging signs of malignancy (no heterogeneity, irregular borders, or growth mentioned). The standard management for non-functional adenomas <4 cm with benign imaging features is clinical observation with repeat imaging at 6 and 12 months to exclude growth, rather than immediate intervention. ## Why each distractor is wrong - **Immediate laparoscopic adrenalectomy due to size >3 cm**: Size alone (3.2 cm) is not an indication for resection. The threshold for increased malignancy risk is >4 cm; <4 cm with benign imaging features warrants observation, not surgery. - **1-mg overnight dexamethasone suppression test and plasma metanephrines measurement**: While hormone testing is part of the initial workup for ANY adrenal incidentaloma to exclude functionality (Cushing, pheochromocytoma, Conn syndrome), the imaging features here are so benign (lipid-rich density, good washout) that the clinical context and imaging already strongly favor a benign adenoma. Testing for functionality is appropriate but is not the "next step" in management decision-making; observation is the management decision. - **Open surgical resection with en-bloc dissection and mitotane chemotherapy**: This aggressive approach is reserved for suspected adrenocortical carcinoma (large size >6 cm, heterogeneity, irregular borders, rapid growth) or functional tumors requiring resection. This mass has no features of malignancy. **High-Yield:** Adrenal incidentaloma <4 cm with unenhanced density <10 HU (lipid-rich) and good washout = benign adenoma → observe with serial imaging; never biopsy without excluding pheochromocytoma first. [cite: Harrison 21e Ch 386; Gray's Anatomy 42e Ch 73]