Ectopic adrenal cortical adenoma arising within the kidney in the setting of adrenal-renal fusion: Two cases mimicking renal cell carcinoma and the role of biopsy and ablation.

Ectopic adrenal cortical adenoma within the kidney is an extremely rare condition that can closely resemble renal cell carcinoma on imaging, especially when occurring in the context of adrenal-renal fusion with a normal native adrenal gland. We present 2 cases of small, enhancing renal masses initially suspected to be malignant based on imaging characteristics. In the first case, CT-guided percutaneous biopsy and microwave ablation were performed, and diagnosis of adrenal-renal fusion was made post procedure upon further histopathologic analysis. In the second case, laparoscopic partial nephrectomy was performed due to suspicion of malignancy, and pathology revealed identical features of an ectopic adrenal cortical adenoma directly fused to renal tissue without a capsule. These cases highlight the importance of understanding the embryologic origin of ectopic adrenal tissue and adrenal-renal fusion, emphasize their radiologic similarity to primary renal tumors, and demonstrate the crucial role of histopathologic confirmation in guiding treatment decisions. Importantly, our findings show that image-guided biopsy can establish a benign diagnosis and enable minimally invasive treatment in selected patients, potentially preventing unnecessary interventions. On follow-up, the ablated patient had no evidence of residual renal lesion on MRI obtained 8 months after treatment. The surgically treated patient has remained without evidence of malignancy, requiring no further oncologic follow-up imaging given the benign pathology.