Adrenal incidentalomas are the classic “we found a mass… now what?” moment on UWorld and in real life. The game is always the same: (1) rule out hormone secretion and (2) assess malignancy risk—fast, systematic, and high-yield.
What counts as an adrenal incidentaloma?
An adrenal mass ≥1 cm discovered incidentally on imaging done for an unrelated reason.
Two must-not-miss questions
- Is it functional (hormone-secreting)?
- Is it malignant (or likely to become a problem)?
The Step-style “3-test” baseline workup (for almost everyone)
Even if the patient “looks fine,” screening is typically recommended because missing these is costly:
- Cortisol excess: 1 mg overnight dexamethasone suppression test (DST)
- Pheochromocytoma: plasma free metanephrines (or 24-hr urinary fractionated metanephrines)
- Primary aldosteronism: aldosterone-to-renin ratio (ARR) only if hypertension and/or hypokalemia
One-liner: Incidentaloma = “DST + metanephrines for all; ARR if HTN/hypoK.”
Visual / mnemonic device: “The Adrenal Hat Trick 🎩 (C-P-A)”
Picture the adrenal wearing a hat with three letters:
- C = Cortisol (Cushing / subclinical hypercortisolism) → DST
- P = Pheo (catecholamines) → metanephrines
- A = Aldo (Conn syndrome) → ARR (if HTN or low K)
Comparison table: Adrenal incidentaloma quick hits (USMLE-ready)
1) Functional causes (what they secrete + how to catch them)
| Condition | Hormone excess | Classic clues | Best screening test(s) | High-yield confirm/next step |
|---|---|---|---|---|
| Pheochromocytoma | Epi/norepi | Episodic headache + sweating + palpitations, paroxysmal HTN | Plasma free metanephrines (most sensitive) or 24-hr urine | Alpha-blockade first (phenoxybenzamine) before surgery; avoid unopposed beta-blockade |
| Cushing syndrome / mild autonomous cortisol secretion | Cortisol | Weight gain, proximal weakness, easy bruising; may be subtle (DM/HTN/osteopenia) | 1 mg overnight DST | If abnormal → additional testing (late-night salivary cortisol, 24-hr urine cortisol) + evaluate ACTH dependency |
| Primary aldosteronism (Conn) | Aldosterone | HTN, often hypokalemic metabolic alkalosis (but K can be normal) | ARR (only if HTN/hypoK) | Confirm (saline infusion, oral salt loading) + subtype (adrenal vein sampling) |
| Androgen-secreting tumor (rare but high-yield red flag) | DHEA/testosterone | Rapid virilization (female) or precocious puberty (child) | DHEA-S, testosterone | Think adrenocortical carcinoma until proven otherwise |
2) Imaging-based triage (benign vs concerning)
| Imaging feature | Suggests | Why it matters (USMLE framing) | Typical next step |
|---|---|---|---|
| Low attenuation on non-contrast CT (lipid-rich) | Benign adenoma | Lipid-rich adenomas look “dark” | Often observe if small and nonfunctional |
| Heterogeneous, irregular borders | Malignancy | Carcinoma/metastasis more chaotic | Surgical evaluation; staging workup |
| Large size (esp. ≥4 cm) | Increased malignancy risk | Size correlates with carcinoma risk | Consider adrenalectomy (context-dependent) |
| Bilateral adrenal masses | Hyperplasia, metastases, hemorrhage, infection | Bilateral disease changes differential | Evaluate systemic causes + hormone screen |
One-liner: Benign adenoma = small + lipid-rich + nonfunctional; concerning = big, ugly, irregular, heterogeneous.
Management: the exam-friendly algorithm
Step 1: Screen for hormones
- Always: DST + metanephrines
- If HTN or hypoK: add ARR
Step 2: Decide surveillance vs surgery (big-picture rules)
Surgery is favored if:
- Functional tumor (pheo, overt Cushing, aldosteronoma, virilizing tumor)
- High malignancy concern (classically large, irregular/heterogeneous, rapid growth)
Observation is favored if:
- Nonfunctional and benign-appearing on imaging
USMLE pearl: Never biopsy an adrenal mass until pheochromocytoma is excluded—biopsy can precipitate a hypertensive crisis.
“Do-not-miss” pearls (high yield)
- Pheochromocytoma triad: episodic headache, sweating, tachycardia; may have sustained or paroxysmal HTN.
- Treatment order in pheo: alpha blockade → then beta blockade (to prevent unopposed alpha vasoconstriction).
- Primary hyperaldosteronism: causes HTN + metabolic alkalosis; potassium can be normal, so don’t rule it out.
- Cushing screening: DST is a go-to because dexamethasone should suppress cortisol in normal physiology via negative feedback.
- Adrenocortical carcinoma clue: rapid onset symptoms + androgen excess; often large and aggressive.
Rapid-fire: shareable summary box
Adrenal incidentaloma = “Is it secreting? Is it scary?”
Workup: DST + metanephrines for all; ARR if HTN/hypoK.
Never biopsy before ruling out pheo.
Alpha then beta for pheo.
Big/ugly/functional → cut it out. Small/benign/nonfunctional → watch it.