Endocrine Abstracts

A usually fit 41-Year-old female was incidentally found to have a 9 cm left-sided adrenal mass during radiological investigations prior to an appendicectomy for acute appendicitis. She did not demonstrate any clinical features of adrenal hormone hyper- or hypofunction.

Investigation: Further investigations were carried out to determine the nature of the mass and biochemically assess adrenal function. These revaled normal metanephrines: plasma metanephrines 151 pmol/l [0.0-510.0], normetanephrine 346.7 pmol/l [0-1180] and 3-Methoxytyramine <75.0 pmol/l [0.0-180]. She had appropriate suppression of cortisol (<50 nmol/l) after a 1 mg overnight dexamethasone suppression test along with a normal 24-hour urinary free cortisol excretion (42 nmol/24h). Serum dehydroepiandrosterone-Sulphate (1.4 umol/l), 17-hydroxyprogesterone (4.8 nmol/l) and testosterone (1.2 nmol/l) were all within normal limits. Radiologically, on dedicated adrenal imaging the large mass was deemed of undeterminate nature and the key differential diagnoses were adrenocortical carcinoma, phaeochromocytoma (the pattern of enhancement suggested this more likely!) and GIST. Further imaging revealed intense localised tracer uptake during an 18-fluorodeoxyglucose positive emission topography (FDG-PET) scan but without uptake on an Meta-Iodo-Benzyl-Guanidine scan (MIBG). 24 hour urinary steroid metabolites screening did not show any abnormalities.

Treatment: She underwent robot assisted laparoscopic left adrenalectomy after multidisciplinary team discussion. Histologically, the tumour demonstrated features consistent with schwannoma. The specimen stained diffusely positive for S100 and SOX 10, with associated patchy expression of GFAP and focal coexpression of AE1/3. All this confirmed the diagnosis of Schwannoma. During the follow-up patient she recovered well from the surgery was empirically treated with hydrocortisone and discharged after a 2-day stay in hospital. A short synacthen test one week later was normal and the patient was weaned off hydrocortisone and fared well since.

Discussion: Adrenal schwannoma is a rare site for a schwannoma to develop. There are no radiological features to suggest schwannoma and hence they should be approached as any other adrenal incidentaloma. The diagnosis is however benign, and surgery is curative with no case report showing any recurrence after prolonged follow-up.