Anastomosing Hemangioma of the Retroperitoneum with Contiguous Renal and Hepatic Involvement: A Rare Benign Vascular Tumor Mimicking Malignancy.

Abstract

Background :
Anastomosing haemangioma (AH) is an uncommon benign vascular neoplasm characterized by
anastomosing capillary-sized vessels lined by bland hobnail endothelial cells. Despite its benign
nature AH frequently mimics aggressive vascular tumors or carcinomas on imaging and intraoperative
assessment. The genitourinary tract especially the kidney, is the most frequently involved site.
Retroperitoneal AH with contiguous involvement of multiple organs is exceedingly rare and poses
significant diagnostic and therapeutic challenges often resulting in radical surgical resections.
Case Report:
A 56-year-old man presented with a short history of vague right upper abdominal pain without
systemic symptoms. Imaging revealed a large heterogeneously enhancing retroperitoneal mass
inseparable from the upper pole of the right kidney with apparent extension into hepatic segments VI
and VII. The imaging findings were strongly suggestive of renal cell carcinoma with hepatic
involvement. Surgical exploration demonstrated a highly vascular mass densely adherent to the right
kidney, liver and adrenal gland prompting en bloc resection with right radical nephrectomy and nonanatomical
hepatic resection. Grossly, the tumor was well circumscribed and adherent to adjacent
organs without definite parenchymal invasion. Histopathological examination showed a wellencapsulated
lesion composed of anastomosing capillary-sized vascular channels lined by bland
hobnail endothelial cells, without cytologic atypia or significant mitotic activity.
Immunohistochemistry revealed diffuse CD34 positivity and a Ki-67 index of less than 1%,
confirming the diagnosis of retroperitoneal anastomosing haemangioma. The postoperative course
was uneventful and no recurrence was noted at three-month follow-up.
Conclusion:
Retroperitoneal anastomosing haemangioma can closely mimic malignant neoplasms radiologically
and surgically particularly when it is large and adherent to contiguous organs. Awareness of this entity
and its characteristic histomorphological and immunohistochemical features is essential to prevent
overtreatment and unnecessary radical surgery.