Anastomosing hemangiomas are benign vascular neoplasms consisting of thin-walled anastomosing vessels. These lesions have been just added to the WHO classification of soft tissue tumors in 2020 as a separate entity 1-3
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Epidemiology
Anastomosing hemangiomas are rare lesions with a wide range of distribution, usually but not exclusively seen in adults with some cases also reported in children 1,4.
Diagnosis
The diagnosis of anastomosing hemangiomas is a histological one 1.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of tumors: soft tissue and bone (5th edition) 1:
anastomosing vascular channels with a hobnail endothelial cell lining
The following histological criterion is desirable:
extramedullary hematopoiesis and hyaline globules
Clinical presentation
Many cases are found incidentally in imaging studies or on endoscopy due to visceral location. Superficial neoplasms might present as palpable nodules or masses with or without associated pain 1. Renal lesions might present with hematuria.
Pathology
Pathologically anastomosing hemangiomas are poorly marginated lesions consisting of thin-walled interconnecting capillary-sized vessels with monolayered endothelial cells featuring a hobnail appearance 1-5.
Etiology
The etiology of anastomosing hemangiomas is unknown 1.
Location
Anastomosing hemangiomas are most commonly seen in the kidneys and retroperitoneum 1-5 but are generally found in multiple locations including the male and female genital tract, gastrointestinal tract, the liver the soft tissues and the skin 1,5.
Macroscopic appearance
Macroscopically anastomosing hemangiomas are well-delineated non-encapsulated lesions with a spongy hemorrhagic mahogany-like appearance 1,5. Tumor size is variable with examples up to 8 cm 4.
Microscopic appearance
Microscopically anastomosing hemangiomas are characterized by the following histologic features 1-5:
loosely lobulated structure
anastomosing capillary-sized vascular channels
scattered single-layered endothelial cells with hobnail morphology and no multilayering
absent or rare mitotic activity
no or at best mild cellular atypia
common vascular thrombi
extramedullary hematopoiesis in a fair number of cases
Immunophenotype
Immunohistochemistry stains show positivity of CD34, CD31 and ERG 1,4,5.
Genetics
Tumors are associated with GNAQ or GNA14 mutations in a majority of cases 1,4.
Radiographic features
On imaging, anastomosing hemangiomas are usually well-marginated, but otherwise, non-specific imaging features 1,4,6. Multifocal lesions have been documented.
Ultrasound
On ultrasound, lesions have been characterized as hypoechoic with plenty of flow signals on color Doppler 7.
CT
On CT lesions have been characterized as hyperdense or hypodense with avid enhancement but heterogeneous attenuation 1,4,7 also due to fatty components 6.
MRI
On MRI anastomosing hemangiomas have been described as well-defined lesions with cystic and solid components 4,7-9. Enhancement patterns have been described as variable, mimicking more aggressive lesions 4,10.
Signal characteristics
T1: hypointense
T2: iso to hyperintense
T1 C+ (Gd): progressive centripetal enhancement
Nuclear medicine
On FDG-PET minor tracer uptake has been observed 9.
Radiology report
The radiological report should include a description of the following:
form, location and size
tumor margins
relation to organs and viscera
relation to muscular fasciae and skeletal muscles in soft tissues
relationship to local nerves and vessels
Treatment and prognosis
Anastomosing hemangiomas are benign lesions even in the setting of multicentricity or infiltrative growth 1. However, due to non-specific imaging features that overlap with several malignant tumors, they are often overtreated 4
History and etymology
Anastomosing hemangiomas have been first described by the American pathologists Elizabeth Montgomery and Jonathan I Epstein in 2009 2,4,5.
Differential diagnosis
Conditions that can mimic the presentation and/or the appearance of anastomosing hemangiomas include the following:
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