Extended Abstract

Introduction
Most kidney tumors originate from epithelial cells, while mesenchymal tumors are considered rare in the kidney. Hemangiomas are benign and rare vascular dysplasias; however, among vascular neoplasms, they are the most common. These tumors can involve visceral organs like the liver and, after the liver, the kidney is the second most common site for visceral hemangiomas.
Renal hemangiomas usually present as solitary and unilateral lesions, with no significant difference in prevalence based on gender or laterality. They most commonly affect individuals from young adulthood to middle age, particularly in the 30-40 year age group. Most hemangiomas measure 1-2 cm in diameter, but cases up to 30 cm have been reported. Symptoms can include flank pain ranging from mild to colicky, potentially due to blood clotting within the vessels. Physical examination may reveal a palpable mass in the flank, and tenderness may also be present.
Renal hemangiomas are slow-growing vascular masses that rarely involve the kidneys. They originate from remnants of pluripotent angioblastic cells, leading to the proliferation of large-diameter vessels. Preoperative diagnosis is challenging because these tumors lack specific radiologic features and are sometimes misdiagnosed as malignant kidney tumors. They are often discovered incidentally during routine imaging or unrelated medical screenings. This case report discusses a middle-aged patient with a cavernous hemangioma, which was surgically removed. Due to its clinical and radiological resemblance to renal cancers, this benign tumor is highlighted.
Case Presentation
A 44-year-old male patient with no clinical symptoms was informed of a mass in his left kidney following an annual abdominal and pelvic ultrasound checkup. The mass was isoechoic with the renal medulla in the lower pole of the left kidney and had minimal vascularity. Further evaluation was carried out after the mass was detected. The patient's physical examination was normal, and he reported no hematuria. Hematology tests and urinalysis were normal. The patient had been taking Livergol (70 mg) for three years due to grade I fatty liver and had a history of aspirin (80 mg) and atorvastatin (20 mg) use for five years up to the time of mass detection. For further diagnostic accuracy, the patient underwent an abdominal and pelvic CT scan.
The CT scan revealed an isodense, endophytic tumor measuring 30 x 20 x 33 mm from the parenchyma of the lower calyx of the left kidney extending towards the renal pelvis. The CT scan suggested a higher likelihood of renal cell carcinoma (RCC) and a lower likelihood of transitional cell carcinoma (TCC), with the tumor staging at T3aN0 based on the TNM system. The renal vein was intact without involvement. Due to suspicion of malignancy, the patient underwent a radical nephrectomy for definitive diagnosis and treatment.
The excised specimen included a kidney measuring 8 x 6 x 5 cm, revealing a hemorrhagic mass with well-defined borders in the renal medulla measuring 1.5 cm in diameter. Histopathologic examination of the sample showed renal parenchyma with a vascular tumor composed of dilated vascular channels lined by normal endothelial cells without atypia and minimal mitosis. Immunohistochemical analysis confirmed the diagnosis, with the sample testing positive for CD34 and negative for PAX8 markers. The final diagnosis was a renal cavernous hemangioma. The patient was discharged in satisfactory condition and advised to follow up regularly.
Conclusion
Preoperative diagnosis of hemangiomas is difficult. Ultrasound examination may show masses with varying echogenicity, often appearing hyperechoic but sometimes hypoechoic. Renal angiography and CT scans can aid in diagnosis, and MRI plays a crucial role in the radiological assessment of urological masses. Selective renal angiography can identify hemangiomas by their characteristic hypervascularity, although they may appear hypovascular due to low flow.
Differential diagnoses for hemangiomas include ectopic papilla, papillary necrosis, angiomyolipoma, intravascular papillary endothelial hyperplasia, hemorrhagic papillitis, urothelial carcinoma, and renal cell carcinoma. Due to the challenges in definitively diagnosing cavernous hemangiomas preoperatively, specific treatments cannot be recommended. If a localized small mass confirmed as a hemangioma exists, kidney-sparing surgery may be performed. Otherwise, radical nephrectomy is the main treatment due to the suspicion of malignancy and the inability to confirm the diagnosis preoperatively.
Histopathologic examination can easily differentiate hemangiomas from malignancies, with subtypes such as capillary, cavernous, and anastomosing hemangiomas identified based on the size of the newly formed vessels. Cavernous hemangiomas consist of dense vascular channels with dilated vessels and erythrocyte accumulation, while capillary hemangiomas show excessive capillary-sized vessel proliferation with minimal stroma. Immunohistochemical analysis can distinguish hemangiomas from malignancies and confirm histopathologic diagnoses. Hemangiomas react to vascular markers like CD34, CD31, Factor VIII, ERG, and FLI-1, whereas RCC and other malignancies react to markers like PAX8, CAIX, CD10, cytokeratins, EMA, CA-9, and PAX2. Follow-up for hemangioma patients varies based on size, extent, and involvement, including monitoring, nephrectomy, heminephrectomy, or papillectomy.

Key Message
Renal cavernous hemangioma is a rare tumor often incidentally discovered during radiography, with treatment involving surgical removal or nephrectomy.