Adrenocortical carcinoma（ACC）is a rare and highly aggressive malignant tumor. Currently，mitotane is the first-line treatment. However，reports on neoadjuvant therapy for ACC using mitotane combined with immune checkpoint inhibitors remain scarce. This article reports a case of ACC. The patient was asymptomatic，and a right adrenal mass was detected during examination. Diagnostic imaging and endocrine evaluation confirmed the diagnosis of ACC. Due to the large tumor size，radical resection was initially considered unfeasible. After 7 months of mitotane therapy and two courses of tislelizumab，significant tumor shrinkage was achieved，allowing for successful open resection of the large right adrenal tumor combined with right nephrectomy. Postoperative histopathological examination confirmed the diagnosis of ACC. During the 3-month postoperative follow-up，no evidence of recurrence or metastasis was observed.

Adrenocortical carcinoma（ACC）is a rare and highly aggressive malignant tumor. Currently，mitotane is the first-line treatment. However，reports on neoadjuvant therapy for ACC using mitotane combined with immune checkpoint inhibitors remain scarce. This article reports a case of ACC. The patient was asymptomatic，and a right adrenal mass was detected during examination. Diagnostic imaging and endocrine evaluation confirmed the diagnosis of ACC. Due to the large tumor size，radical resection was initially considered unfeasible. After 7 months of mitotane therapy and two courses of tislelizumab，significant tumor shrinkage was achieved，allowing for successful open resection of the large right adrenal tumor combined with right nephrectomy. Postoperative histopathological examination confirmed the diagnosis of ACC. During the 3-month postoperative follow-up，no evidence of recurrence or metastasis was observed.