Man in his 60s with a periureteral mass   


Anastomosing hemangioma

Anastomosing hemangiomas (AH) are benign vascular tumors. Originally described in the genitourinary (GU) tract, AH has also been described in recent decades in soft tissue, with more predilection to the paraspinal areas. The most common sites of involvement are the soft tissues, GU tract, gastrointestinal tract, and liver. Grossly, AHs are well-demarcated, with a hemorrhagic, mahogany, spongy cut surface. AHs are benign vascular tumors with essential features that overlap with well-differentiated forms of angiosarcoma with anastomosing sinusoidal capillary-sized vessels. Mild endothelial nuclear variability and scattered, hobnailed endothelial cells are noted. Fibrin thrombi are typical; 50% of cases show extramedullary hematopoiesis and mature fat. Mitotic activity is rare. AH is positive for endothelial markers (CD31, CD34, ERG) and negative for HHV8. This tumor is usually cured with simple excision.

AH’s differential diagnosis includes benign and malignant vascular lesions; it is commonly mistaken for a malignant angiosarcoma. The differential diagnosis for AH includes the following, with distinguishing features:

  • Angiosarcoma: Diffusely infiltrative growth pattern, high-grade cytologic atypia, multilayering of endothelial cells, and mitotic activity
  • Retiform hemangioendothelioma: More common in distal extremities with resemblance to rete testis
  • Hobnail hemangioma: Dilated wedge-shaped vascular channels
  • Encapsulated accessory spleen
  • Splenosis: Positive for CD8


  1. Montgomery E, Epstein JI. Anastomosing hemangioma of the genitourinary tract: A lesion mimicking angiosarcoma. Am J Surg Pathol. 2009;33(9):1364-1369. doi: 10.1097/PAS.0b013e3181ad30a7.
  2. John I, Folpe AL. Anastomosing hemangiomas arising in unusual locations: A clinicopathologic study of 17 soft tissue cases showing a predilection for the paraspinal region. Am J Surg Pathol. 2016;40(8):1084-1089. doi: 10.1097/PAS.0000000000000627.
  3. Lin J, Bigge J, Ulbright TM, Montgomery E. Anastomosing hemangioma of the liver and gastrointestinal tract: An unusual variant histologically mimicking angiosarcoma. Am J Surg Pathol. 2013;37(11):1761-1765. doi: 10.1097/PAS.0b013e3182967e6c.
  4. Brown JG, Folpe AL, Rao P, et al. Primary vascular tumors and tumor-like lesions of the kidney: a clinicopathologic analysis of 25 cases. Am J Surg Pathol. 2010;34(7):942-949. doi: 10.1097/PAS.0b013e3181e4f32a.