[Adrenocortical cancer: morphological variants, immunohistochemical characteristics]

Adrenocortical cancer (ACC) is a rare endocrine malignancy of the adrenal cortex, which has an unfavorable prognosis and extremely aggressive clinical behavior in most cases. Nevertheless, cases of a more favorable disease course with late metastasis and slow progression have been described. In 2017, the International Agency for Research on Cancer (IARC) and the World Health Organization (WHO) in the 4^th edition of the Classification of Tumors of the Endocrine Organs identified histological variants of ACC, such as classical, oncocytic, myxoid, and sarcomatoid ones, indicating the morphological heterogeneity of this tumor.

To provide a detailed description of the morphological variants of ACC with an emphasis on their histological characteristics and the expression of immunohistochemical markers.

A total of 75 cases of ACC were analyzed in the adult population diagnosed as having the morphological variants in accordance with the International Histological Classification of Adrenal Tumors (WHO, 2017). Monoclonal antibodies to SF1, Inhibin A, Melan A, Ki-67, p53, and antimitochondrial antibodies were used for immunohistochemical diagnosis.

The classic, oncocytic, and myxoid subtypes of ACC were found in 51 (68%), 15 (20%), and 9 (12%) cases, respectively. The functional activity of the tumors was observed in 43% (n=18) in the classic variant of ACC; moreover, the clinical picture was manifested by the symptoms of hypercorticism (38%) and virilization (5%). There were no significant differences in hormonal activity between different morphological variants. The characteristics of the above histological variants of the tumor was determined with a description of growth patterns that can improve the diagnosis of ACC. The diagnosis of ACC can be confirmed by an immunohistochemical study; the required minimum panel of markers should include SF1, Melan A, and Inhibin A. The Ki-67 proliferative activity index showed significant differences (p=0.0056) when it was determined in the morphological variants of ACC.

Despite the determination of a minimal immunohistochemical panel to confirm the diagnosis of ACC, it is important to remember that each histological variant may be characterized by the different expression of immunohistochemical markers. The identification of morphological variants of ACC and the use of specific, sensitive, and prognostically significant immunohistochemical markers will allow clinicians and pathologists to more accurately judge the biological properties of this tumor and the clinical course of the disease.