Histopathological study of adrenocortical carcinoma with special reference to the Weiss system and TNM staging and the role of immunohistochemistry to differentiate it from renal cell carcinoma

Abstract

Adrenocortical carcinomas (ACC) are rare tumors with an incidence of 1-2/million/year. They account for 0.05-0.2% of all malignancies. This study was aimed to evaluate the Weiss system to diagnose ACCs and to compare it with TNM staging. The role of immunohistochemistry (IHC) was also evaluated to differentiate ACC from other differential diagnoses especially, renal cell carcinoma (RCC). A total of 10 ACCs were included from April, 2000 to March, 2012. All the relevant information like weight, tumor size, gross features was recorded. Multiple sections were taken for histologic examination. Immunomarkers like vimentin, synaptophysin, Melan-A, calretinin, inhibin, EMA, cytokeratin, and Ki-67 were used. Out of 10 cases of ACCs (diagnosed by the Weiss system), the tumors were in TNM stage I (1 case), stage II (2 cases), stage III (5 cases), and stage IV (2 cases). The Weiss score in stages I-IV was 4; 5-7; 6-8; and 5-9 respectively. ACCs were positive for vimentin, inhibin, Melan-A, calretinin and negative for EMA and cytokeratin. Proliferative index (Ki-67/MIB-1) was ≥ 20 % (20-65%). Both the Weiss system and TNM staging are useful in predicting the malignant behavior and prognosis of ACC. Weight and tumor size, though originally not included in the Weiss system, are also important parameters. In lower stages (stages I and II), the Weiss score is low (4-7) while the score is high (6-9) when the tumor is in higher stages (stages III and IV). IHC plays a vital role to confirm the diagnosis and to exclude the possibility of RCC.