Endocrine Abstracts

Background: Adrenocortical carcinoma (ACC) is an uncommon endocrine malignancy, usually characterized by a late detection, aggressive clinical course, and poor outcome. The tumor microenvironment (TME) which includes infiltrating immune cells plays a critical role in tumor growth, survival, and prognosis in cancer patients. The presence of tumor-infiltrating immune cells (TIIC) affect the clinical benefit from novel strategies of immunological checkpoint blockade. Anti-immune pathways like PD-L1 are used by the tumor to overcome immune system and they serve as immunotherapy targets.

Methods: The study included tumor tissue samples from 75 patients with ACC, which treated at the Endocrinology Research Centre (Russia, Moscow) between 2010 and 2022: 47 cases of conventional (62.7%), 18 cases of oncocytic (24%), and 9 cases of myxoid (12%) and 1 case of sarcomatoid (1.3%) variants of ACC. Immunohistochemical analysis of tumor tissue sections was carried out according to the standard technique with a peroxidase detection system with DAB on an automatic Leica BOND III IHC staining system using Leica reagents and protocols. Each of the 75 patients underwent histological diagnostics and a series of immunohistochemical stains for the markers of the main immune cell subsets: CD45, CD3, CD4, CD8, and CD68. The impact of PD-L1 expression and the number of TIIC considering the intratumoral and stromal distribution on pathological characteristics and clinical outcomes were analysed.

Results: The number of ?D45+ immune cells in tumor parenchyma and stroma was 189 and 268 cells/mm², respectively. However, the number of immune cells from all the analyzed populations in tumor parenchyma was higher in oncocytic compared to conventional ACC cases. The analysis of the relationship of survival with the studied factors showed that the overall survival and progression-free survival between conventional and oncocytic histological variants differ significantly. The differences in survival between conventional and oncocytic histological variants of ACC were statistically significant (P-value < 0.05). PD-L1 expression does not affect prognosis.

Conclusions: Rich T-lymphocyte response is a good prognostic factor in ACC. The study of TIIL subpopulations can be used to predict ACC outcomes.