Pseudomyogenic hemangioendotheliomas, also known as epithelioid sarcoma-like hemangioendotheliomas, are locally aggressive and rarely metastasizing vascular neoplasms with histological similarities to myoid tumors and epithelioid sarcomas.
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Epidemiology
Pseudomyogenic hemangioendotheliomas are rare and mostly seen in men. They occur in young adults, particularly in the 3rd and 4th decades of life. Only about a fifth is seen after the age of 40 years. Approximately 60% of the patients have multifocal disease 1-3.
Diagnosis
The diagnosis of composite hemangioendothelioma is established by histologic and molecular pathologic features 1.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 1:
- plump spindled to epithelioid cell morphology with bright cytoplasm
- sheet-like or fascicular growth pattern
- positivity of ERG, FOSB and keratins
The following histological criterion is desirable in selected cases:
- FOSB gene rearrangement
Clinical presentation
About half of the lesions are painful with the other half being indolent and many lesions present as possibly ulcerating cutaneous or subcutaneous nodules. Lesions of the deeper soft tissues and bone might be incidentally detected on imaging 1-3.
Pathology
Pseudomyogenic hemangioendotheliomas are often multifocal endothelial proliferations forming multiple separate nodules in distinct tissue planes. It lacks any frank histological vascular differentiation and resembles epithelioid sarcoma or myoid tumors, but expresses vascular features on immunohistochemistry stains 1-3.
Etiology
Pseudomyogenic hemangioendotheliomas have an unknown etiology 1.
Location
Pseudomyogenic hemangioendotheliomas are often multifocal with the involvement of different anatomic tissue planes and body regions. The skin and subcutaneous tissues are affected in three-quarters of the cases. About half of the patients have intramuscular lesions and still a number as high as 20% show an osseous involvement. Lesions are usually found in the lower extremity, whereas the upper limb and trunk are less frequently involved. The head and neck region is a rare site 1-3.
Macroscopic appearance
Macroscopically pseudomyogenic hemangioendotheliomas usually appear as smaller nodules rarely being larger than 3 cm with ill-defined borders of tannish-grey or white color and a firm consistency 1-3.
Microscopic appearance
The histological spectrum of pseudomyogenic hemangioendotheliomas includes the following features 1-3:
- sheet-like or fascicular growth pattern
- spindle cells and epithelioid cells with eosinophilic cytoplasm
- no obvious vascular differentiation
- variable inflammatory infiltrates
- possible desmoplastic reaction
- mild nuclear atypia and mitotic activity
- rarely pleomorphism
- infiltration of the surrounding tissues
Immunophenotype
Immunohistochemistry stains are usually positive for keratin, ERG FLI1 and FOSB. CD31 and smooth muscle actin are other markers that might be expressed. CD34 is usually negative 1-3.
Genetics
FOSB gene rearrangements with a fusion of the SERPINE1-FOSB or ACTB-FOSB have been demonstrated. Both gene fusions show similar clinical and pathological features, although solitary lesions seem to be more common with the ACTB-FOSB gene fusion 1,2.
Radiographic features
On imaging pseudomyogenic hemangioendotheliomas usually appear as lobulated and well-defined lesions 2. Due to the occurrence in different anatomic tissue planes cross-sectional has an important role in the diagnosis and localization of the disease. However, there might be discordant findings across different imaging modalities 4.
Plain radiograph
Plain radiographs might detect bony involvement as well-demarcated osteolytic lesions involving cortical or cancellous bone or both 5.
CT
Osseous lesions have been described as expansile osteolytic and well-demarcated without signs of bone destruction or periosteal reaction 2,4,5. Soft tissue lesions might appear as non-specific lobulated well-delineated soft tissue mass.
MRI
MRI imaging has been reported to show expansile well-delineated heterogeneous lesions often multiple 4-6.
Signal characteristics
- T1: low to intermediate signal intensity
- T2: variably high signal intensity
- T2FS/STIR: variably high signal intensity
- T1 C+ (Gd): homogeneous to a mildly heterogeneous enhancement
Nuclear medicine
PET-CT
PET-CT has been reported to show an intense FDG uptake 6.
Radiology report
The radiological report should include a description of the following:
- form, location and size
- tumor margins
- relation to the muscular fascia
- relationship to bones, tendons and joints
- relationship to local nerves and vessels
Treatment and prognosis
Due to the rare occurrence, optimal management is still somewhat unclear. Treatment usually consists of wide surgical excision possibly with adjunctive chemo- and/or radiotherapy. Local recurrence or appearance of additional nodules is common and occurs in about 60% of patients with a short recurrence time interval of 1-2 years. Lymph node metastases or distant metastases to lungs, bones and soft tissues are infrequent but can occur even decades after the initial presentation 1-3.
History and etymology
The tumor was first termed epithelioid sarcoma-like hemangioendothelioma on the first description by the American pathologist Steven D. Billings and colleagues in 2003 7 and later named pseudomyogenic hemangioendothelioma in 2011 by the American pathologist Jason L. Hornick and British pathologist Christopher DM Fletcher 8.
Differential diagnosis
The differential diagnosis of pseudomyogenic hemangioendotheliomas also depends on the location of the tumor and consists of the following 1-3:
- cutaneous/subcutaneous tissues
- epithelioid sarcoma
- sarcomatoid carcinoma
- cellular fibrous histiocytoma
- leiomyosarcoma
- deep soft tissues
- bone
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