Delayed Clinical Manifestation of Malignant Potential in a Cortisol‐Secreting Adrenal Tumor Initially Diagnosed as Adenoma

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.