Myxoid and Sarcomatoid Variants of Adrenocortical Carcinoma: Analysis of Rare Variants in Single Tertiary Care Center

The aim of this study is to describe rare variants of adrenocortical carcinoma (ACC) and to compare the prognosis with that of conventional ACC. We retrospectively reviewed 8 cases of myxoid variant, 1 sarcomatoid variant, and 14 cases of conventional ACC, who underwent surgical resection at the Asan Medical Center between 1996 and 2014. An analysis of the clinicopathological characteristics, including the Weiss score, Ki-67 labeling index, and reticulin framework assessment is presented. The mean age of patients with myxoid/sarcomatoid ACC was 45 years; 4 out of 9 patients were women. Mean primary tumor size was 12.9 cm and the mean weight was 702.4 g. Seven patients presented in an advanced stage (stage III/IV); 8 of these eventually developed distant metastasis. The mean Weiss score was 5.0 points and the Ki-67 labeling index was 15.6%. The extent of myxoid or sarcomatoid change on histological examination ranged from 10% to 75% of the examined tumor areas; reticulin framework alteration was observed in all cases. Four patients showed venous tumor thrombus. Most of the clinicopathological parameters were not significantly different from those of conventional ACC. However, myxoid or sarcomatoid variant (hazard ratios [HR], 3.59; 95% confidence intervals [CI], 1.13-11.38; P = 0.030) and Ki-67 labeling index (HR, 3.97; 95% CI, 1.18-13.41; P = 0.030) were independent predictors of overall survival after adjusting for age and sex. Myxoid or sarcomatoid histological features or an increased Ki-67 labeling index may be associated with poor overall survival in patients with ACC.