56. Oncocytic adrenocortical neoplasms – a clinicopathological study of 13cases

Background Oncocytic adrenocortical neoplasms (OAN) are a rare but important subtype of adrenal tumours composed predominantly of oncocytes. Aims To present 13 new cases of OAN and review all published cases in the literature to date with emphasis on prognosis. Materials and methods Our combined databases were searched to identify all potential cases. Only tumours composed of 90% or more oncocytes were included. The Lin-Weiss-Bisceglia (LWB) criteria were applied for assessment of malignant potential. All published cases were reviewed and survival was calculated from follow-up data using the Kaplan-Meier method. Results There were 7 females and 6 males with median age of 41 years. Seven showed evidence of endocrine overproduction. Median size was 80 mm and median weight was 155 g. All cases were composed of oncocytes organised predominantly in sheets with variable trabecular, alveolar and microcystic patterns. Small cell change was a frequent finding. Majority stained positively with vimentin, synaptophysin, inhibin, melan-A, calretinin and the antimitochondrial antibody, mES-13. Three were classified as benign, 2 as borderline and 8 as malignant according to LWB criteria. Three recurrences and 3 deaths occurred in malignant group. A total of 109 cases have been published to date. From follow-up data, the estimated median survival for malignant OAN is 58 months (95%CI 27.5–88.5 months), slightly longer than commonly quoted figures for conventional adrenocortical carcinomas (ACC). Conclusion OAN are an important clinicopathological subtype for pathologists to recognise due to their unique clinical and morphological features. Our analysis provides preliminary evidence that the prognosis of malignant OAN may be more favourable than conventional ACC.