2021-14/ April 5
Contributors: Paige Parrack and Andres M. Acosta

A man in his late 50s with a history of unclassified renal cell carcinoma status post left nephrectomy, adrenocortical adenoma, and angiomyolipoma, was found to have a 1.3 cm round soft tissue mass near the right diaphragmatic crus. A core biopsy of the mass was obtained for evaluation.


1. What is the correct diagnosis?

a. Angiosarcoma

b. Anastomosing hemangioma

c. Metastatic renal cell carcinoma

d. Angiomyolipoma

e. Kaposi sarcoma

1. Anastomosing hemangioma

On H&E, the core biopsy showed irregular, anastomosing capillary-sized vascular channels. The channels were lined by a single layer of bland endothelial cells with focal hobnail morphology. Additionally, the lesion contained patchy intracytoplasmic hyaline globules and scattered intravascular fibrin thrombi. An ERG immunostain was positive in the endothelial cells lining the vascular spaces, and a SMA immunostain showed diffuse staining of the pericytes. Immunostains for HMB-45, PAX8, and Melan-A were negative. Within this specimen, there was no evidence of necrosis, nuclear hyperchromasia, mitotic activity, multi-layered endothelium, or extramedullary hematopoiesis.

Anastomosing hemangiomas are rare vascular neoplasms that have been reported predominantly in the kidney but have also been identified in the soft tissue (particularly paravertebral), testis, ovary, adrenal gland, liver, and GI tract. Resection of these cases are described as grossly well-demarcated and unencapsulated. This entity is typically characterized by the aforementioned histologic findings, although a subset of cases has extramedullary hematopoiesis. Some anastomosing hemangiomas have been reported to have a focally infiltrative pattern. A study by Bean et al. (1) analyzed the molecular characteristics of anastomosing hemangiomas and discovered a mutational hotspot in codon 209 of GNAQ. Mutations in GNAQ are not specific for anastomosing hemangiomas and have also been described in other vascular tumors such as congenital hemangiomas, capillary malformations in Sturge-Weber syndrome, and hepatic small vessel neoplasms.

Anastomosing hemangiomas are benign vascular neoplasms that can be mistaken for aggressive neoplasms such as angiosarcoma and Kaposi sarcoma. This can lead to a diagnostic dilemma, especially regarding small biopsy specimens, but uniform histologic features and a focused immunohistochemistry panel can be used to distinguish anastomosing hemangioma from these morphologic mimics.

1. Bean GF, Joseph NM, Gill RM, Folpe AL, Horvai AE, Umetsu SE. Recurrent GNAQ mutations in anastomosing hemangiomas. Modern Pathology. 2017 January; 30: 722-727.

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 August; 40(8):1084-1089.

3. Lappa E, Drakos E. Anastomosing hemangioma: A Short Review of a Benign Mimicker of Angiosarcoma. Arch Pathol Lab Med. 2020 February; 144: 240-244.

4. Montgomery E, Epstein JI. Anastomosing Hemangioma of the Genitourinary Tract: A Lesion Mimicking Angiosarcoma. Am J Surg Pathol. 2009 September; 33(9):1364-1369.

Paige Parrack
Andres Acosta
Brigham and Women’s Hospital
Boston, MA

Abdominal soft tissue

Hemangioma; soft tissue; vascular; anastomosing