Abstract
INTRODUCTION: Distinguishing adrenocortical carcinoma (ACC) from adenoma is often difficult, particularly in hormonally active tumors with borderline histologic features. CASE PRESENTATION: A 55-year-old woman presented with abdominal distension and central obesity. Hormonal evaluation confirmed ACTH-independent Cushing's syndrome. Imaging revealed a 60-mm left adrenal mass. Laparoscopic adrenalectomy was performed; pathology was initially interpreted as cortical adenoma with mild nuclear atypia and a Ki-67 labeling index of 6%. The patient remained disease-free until year three postoperatively when rising cortisol levels and surveillance imaging revealed a 36-mm retroperitoneal mass. Open nephrectomy and tumor excision were performed. Histopathology confirmed ACC. Retrospective review of the initial specimen revealed features consistent with early carcinoma. CONCLUSION: This case illustrates that cortisol-producing adrenal tumors initially diagnosed as adenomas may harbor unrecognized malignant potential, which can become clinically evident several years after surgery.