Multicentric Retrospective Analysis of Oncocytic Adrenocortical Carcinoma: Insights into Clinical and Management Strategies

: Oncocytic adrenocortical carcinoma (OAC) is a rare variant of conventional adrenocortical carcinoma (ACC), characterized by oncocytic tumor cells comprising more than 90% of the tumor. Due to its rarity, there is a lack of reliable data on the clinicopathological features and outcomes of OAC. The aim of this study was to assess the clinical presentation, treatment modalities, and outcomes of patients with OAC, comparing these results with a cohort of patients with conventional ACC. Data from 9 referral centers in Italy on 44 patients with OAC were retrospectively analyzed and compared with data from 145 patients with conventional ACC. Patients with OAC had a smaller median tumor size, more favorable resection margin status, and lower incidences of venous invasion and persistent/recurrent disease during follow-up. Additionally, patients with OAC exhibited longer times to progression (TTP) and overall survival (OS) compared to patients with conventional ACC. Multivariable analyses identified Ki67 and tumor size as features independently associated with disease progression during post-surgical follow-up, while Ki67 and distant metastases at diagnosis were independently associated with OS in OAC patients. After complete tumor removal, the risk of recurrent disease was higher in patients with either Ki67 ≥ 20% or ENSAT stage III/IV. OAC appears to have a more indolent clinical course and better prognosis than conventional ACC. Similar to conventional ACC, Ki67 remains a significant prognostic marker for OAC and, along with ENSAT stage, serves as a reliable biomarker for identifying patients who may benefit from adjuvant mitotane therapy.