Differential Diagnosis for Redemonstrated Left Renal Mass in the Midpole

Single Most Likely Diagnosis

• Renal Cell Carcinoma: This is the most common primary malignancy of the kidney in adults, and a midpole location is consistent with its typical presentation. The fact that the mass has been re-demonstrated suggests a growing or persistent lesion, which raises concern for malignancy.

Other Likely Diagnoses

• Simple Renal Cyst: While simple cysts are common and usually benign, a complex cyst or one that has changed in size could be concerning and might require further evaluation to rule out malignancy.
• Angiomyolipoma: A benign tumor composed of blood vessels, smooth muscle cells, and fat cells. It is a common cause of renal masses and can be diagnosed based on the presence of fat within the lesion on imaging.
• Onocytoma: A benign renal tumor that can mimic renal cell carcinoma on imaging. It is typically well-circumscribed and may have a central scar.

Do Not Miss Diagnoses

• Metastasis: Although less common, metastatic disease to the kidney from other primary sites (e.g., lung, breast, melanoma) can present as a renal mass. Missing this diagnosis could significantly impact treatment and prognosis.
• Lymphoma: Renal involvement by lymphoma can occur and may present as a mass. This diagnosis is critical due to its implications for systemic disease and treatment.
• Infectious or Inflammatory Processes: Such as abscesses or pyelonephritis, which could present as a mass on imaging. These conditions require prompt diagnosis and treatment to avoid serious complications.

Rare Diagnoses

• Juxtaglomerular Cell Tumor: A rare, usually benign tumor that can cause hypertension due to renin secretion.
• Renal Leiomyoma: A rare, benign smooth muscle tumor of the kidney.
• Renal Hemangioma: A rare, benign vascular tumor of the kidney.
• Cystic Nephroma: A rare, benign multilocular cystic lesion of the kidney, which can be difficult to distinguish from a malignant process without histological examination.

Each of these diagnoses has different implications for patient management, ranging from watchful waiting for benign conditions to urgent surgical or medical intervention for malignant or potentially life-threatening conditions.