Incidental Adrenal Nodule in a Patient with Prior Breast Cancer
A 61-year-old woman with a history of stage II ER-positive breast cancer treated with lumpectomy, radiation, and adjuvant endocrine therapy 5 years ago undergoes a CT of the chest and abdomen for surveillance. She is asymptomatic. The CT is performed with IV contrast in the portal venous phase. A 2.8 cm well-circumscribed left adrenal nodule is identified. The nodule measures 18 HU on the unenhanced images (which were also acquired) and 62 HU on the portal venous phase. There is no washout phase. The rest of the study shows no evidence of recurrence. Her most recent tumor markers are normal. The ordering oncologist asks whether this represents metastatic disease.
1. How should the adrenal nodule be characterized, and what is the appropriate next step?
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The key discriminator is the unenhanced attenuation. A nodule ≤10 HU on unenhanced CT is essentially diagnostic of a lipid-rich adenoma and requires no further workup. This nodule measures 18 HU, which is indeterminate (above the 10 HU threshold but below the ~20 HU range often seen with lipid-poor adenomas).
The portal venous enhancement (62 HU) is nonspecific and cannot distinguish adenoma from metastasis. Because no delayed/washout phase was obtained, the standard next step is a dedicated adrenal protocol CT with unenhanced, enhanced, and 15-minute delayed phases to calculate absolute and relative washout. Absolute washout >60% (or relative >40%) supports adenoma. If washout is indeterminate, chemical-shift MRI or FDG-PET/CT can be considered.
Given her history of breast cancer, metastasis is a real consideration, but breast cancer adrenal metastases are less common than in lung cancer; the probability still favors a benign incidentaloma. The nodule is >1 cm and indeterminate, so it warrants characterization rather than dismissal. Biopsy is reserved for lesions that remain indeterminate after washout and MRI/PET, and only if the result would change management.
2. If the washout study confirms a lipid-poor adenoma, how does her cancer history change follow-up?
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It does not change the diagnosis, but it changes the surveillance intensity. A confirmed adenoma in a patient with a known malignancy can generally be managed with the same approach as any incidentaloma - no specific adrenal follow-up is required if it is biochemically silent and imaging-confirmed benign. However, because she has an active surveillance relationship, it is reasonable to document the finding and re-image the adrenal gland at the next scheduled oncologic surveillance scan (typically 6–12 months) rather than ordering a dedicated adrenal follow-up.
The more important point is biochemical: any adrenal incidentaloma should be screened for hormonal hypersecretion (plasma metanephrines, overnight dexamethasone suppression test, and, if hypertensive, aldosterone/renin), regardless of cancer history. Imaging alone does not exclude a functional adenoma. If she has hypertension or hypokalemia, the aldosterone workup becomes more pressing.