...ADRENAL INCIDENTALOMA
This is the 3rd post about this issue. You can find the original article here and previous posts number 1 here and number 2 here .
IMAGE WORK-UP
- All images > 10 mm must be evaluated for malignancy risk
- Clearly benign images like cysts or lipid-rich ones (myelolipomas) do not need further investigation.
- Size is clearly correlated to malignancy risk: 2% in <4 cm, 6% in 4-6 cm, 35% in >6 cm. 90% of cancers are > 4 cm.
- Other characterystics are displayed by different radiologic techniques:
- Unenhanced CT. First-line study. HU (arbitraty units of attenuation value, water being 0) <10 clearly suggests benign lesions. Care should be exercised in unhomogeneous images.
- Contrast-enhanced CT washout. 30% of adenomas are poor in lipids and have >10 HU, overlapping with PhCC and ACC. All three lesions take up contrast rapidly but adenomas show pronpt washout and the other not. Measurement at 1-2 min and 10-15 min washout rate may be calculated, being >60% suggestive of adenomas, but some PhCC can also wash out rapidly.
- Dual Energy CT. It can provide additional information about composition of images, but further research is needed to estimate its role in AI evaluation.
- MRI with chemical shift (in-phase/out of phase). Very useful in assessing lipid content. Could be first-line study in children or pregnant. If an AI is discovered by a MRI and is clearly lipid-rich, no further studies are neccesary.
- PET/CT has sensitivity and specificity of 90%, false-negatives in small or nod FDG-avid metastases, false-positives in metabolicaly active adenomas and PhCC. More useful to rule-out metastases in patients with known cancers or previous to surgery.
FOLLOW-UP
- No need to follow up images <4 cm with benign characterystics
- Benign images >4 cm: image reassessment in 6-12 months.
- Discuss in multidisciplinary team (MDT) with endocrinologists, surgeons, pathologist, radiologist, nuclear medicin specialists, when:
- no clear benign image
- growth in follow up
- hypersecretion (mostly ACS, view post 2)
- considering surgery
BILATERAL AI
- Initial considerations
- Both masses must not be the same, if hypersecretion, maybe only one is secreting.
- Always consider adrenal insufficiency, mostly in metastases and hemorrhages.
- Autonomous Cortisol Secretion (ACS)
- ACS is twice as frequent (35 vs 18%) in bilateral adrenal enlargement
- Primary Bilateral Macronoduar Adrenal Hyperplasia (PBMAH) should be suspected in ACS + bilaterality. Etiology: aberrant G protein coupled receptors, not for ACTH, but able to activate downstream pathways
- Unenhanced CT may or not show nodules. When present, nodules may have >10 HU and be positive on PET. Be careful!
- Surgery is recommended in PBMAH + ACS when UFC >3xnormal range. Bilateral excision is indicated in symmetrical enlargements. In selected cases with asymmetry unilateral adrenalectomy may be performed, but although initial remission is high (85%), long-term results are poor (30%).
- Congenital Adrenal Hyperplasia (CAH). Rare in adults, suspect only when elevated ACTH. Suppresed ACTH suggests malignancy or PBMAH even if elevated 17OH prog.
- Pheochromocytoma. 10% are bilateral, mostly in genetic syndromes.
- Metastases.
- 75% of patients with known malignancy and AI have methastases, the other 25% are primary adrenal lesions.
- Adrenal insufficiency is rare even in bilateral metastases but must always be evaluated.
BIOPSY
- Generally not indicated for three reasons:
- No able to differenciate adrenal adenoma and carcinoma.
- Risky if pheochromocytoma.
- Seeding adrenal cancer
- If known malignancy and suspected metastases that would affect management biopsy is indicated in selected cases.
Next post: surgery, nonsurgical follow-up, and future research.
