Rationale: Vascular tumours of the kidney are a heterogeneous group of lesions showing common characteristics with malignant neoplasms, making it significantly challenging the pre-operative diagnosis. Among these lesions, Anastomotic Hemangioma (AH) is a recently recognised variant of hemangioma of the genito-urinary tract characterized by a complex vascular structure. This manuscript presents the case of a 85-year-old caucasian woman diagnosed with renal sinus AH.

Patient concerns: The man was admitted to the hospital with a 4-month history of a left renal mass discovered by ultrasound (US) of the abdomen performed for an elevation of transaminases, in the absence of significant genito-urinary symptoms. We performed radiological examinations through Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) that revealed a lesion showing apparently malignant characteristics. The multidisciplinary team decided to proceed with nephrectomy. The postoperative pathological examination revealed that the mass contained capillaries arranged in a characteristic anastomotic or confluent pattern commonly seen in AHs.

Outcomes: The mass was successfully removed. The follow-up examination at 7 months post-surgery showed that the patient recovered well, and no recurrence or metastasis was found.

Conclusion: Anastomotic renal sinus haemangioma is a rare benign vascular tumor. On imaging examinations, AHs appear as mostly heterogeneous masses with peripheral and/or pseudonodular enhancement. However, a definitive diagnosis can only be achieved through histopathological examination.