Hemangiopericytoma is a rare mesenchymal tumor, typically located in the retrobulbar intraconal space of the orbit, that is generally slow-growing, but has malignant potential.
Hemangiopericytoma is most commonly encountered in the orbit, but can be located in the conjunctiva, choroid, optic nerve or medial canthal skin. Hemangiopericytoma makes up 1-3% of all biopsied orbital lesions and 1% of all lacrimal sac tumors. The mean age of onset of orbital hemangiopericytoma is 42 years, however lacrimal sac hemangiopericytoma has a slightly earlier age on onset. Hemangiopericytoma affects males and females equally and no racial differences have been observed.
Controversy exists regarding the diagnosis of orbital hemangiopericytoma as it shares many characteristics with fibrous histiocytoma and giant cell angiofibroma of the orbit. Some pathologists recommend classifying all three tumors as solitary fibrous tumors.
Cells in hemangiopericytomas are derived from pluripotent perivascular mesenchymal cells and resemble pericytes, with few cytoplasmic organelles. Thin-walled, branching blood vessels, also known as “staghorn” vessels, are characteristic of hemangiopericytomas. Nuclei are often ovoid or spindle shaped. The masses are generally well-circumscribed or encapsulated (75%). Hemangiopericytomas uniformly stain positively for CD34 and vimentin . 70% are Leu-7 positive. Factor XIIIa and HLA-DR may also be present in some hemangiopericytomas. It has also been shown that signal transducer and activator of transcription 6 (STAT6) could be a useful diagnostic marker for solitary fibrous tumors.
30% of orbital hemangiopericytomas are histologically compatible with malignancy. Findings that indicate a worse prognosis include high mitotic rate, increased cellularity, pleomorphism, necrosis and hemorrhage. Other prognostic markers include Bcl-2, p53 and Ki-67.
History and Clinical Presentation
Clinical presentation varies significantly, with the most common presenting complaint of a painful or painless orbital mass. Patients may present with proptosis, diplopia, orbital pressure or pain . Patients with lacrimal sac hemangiopericytomas may present with a painless mass near the medial canthus. They may also present with epiphora, which may be bloody. Subconjunctival hemangiopericytoma is rare, however case studies have identified patients presenting with visible masses and subconjunctival bleeding after sneezing.
Orbital hemangiopericytomas occur most frequently in the superior orbit, equally distributed between the medial and lateral orbit. Masses may be visible on exam if located in the subconjunctival space or lacrimal sac. Lacrimal masses tend to be ballotable on palpation. Vision may be decreased, proptosis may be measured on exophthalmometry, and motility may be limited depending on the size and location of the mass.
Further diagnostic testing may include CT or MRI imaging of the lesion to delineate anatomical relationships for surgical planning. Radiology typically demonstrates a well-circumscribed, round, retrobulbar mass, often within the muscle cone, although it can be located extraconally. However, definitive diagnosis requires histopathologic evaluation of the lesion. If metastases are clinically suspected, workup should include relevant imaging.
- Fibrous histiocytoma
- Glomus tumor
- Biphasic sarcomas
- Synovial sarcoma
- Kaposi’s sarcoma
- Vascular malformation
Medial canthal mass
- Fibrous histiocytoma
- Lymphoid tumors
- Granulocytic sarcoma
- Squamous cell carcinoma
The role of chemotherapy is unclear in the treatment of hemangiopericytoma. Recent studies have shown limited benefit of preoperative ifosfamide and epirubicin. Studies of preoperative radiation have also been inconclusive.
Medical follow up
A multidisciplinary management approach in conjunction with the primary care physician and oncologist is recommended.
Definitive treatment for hemangiopericytoma is a complete local excision including the capsule. Excellent hemostasis is important intraoperatively due to the highly vascular nature of hemangiopericytomas. There have been case reports using embolization techniques with n-butyl cyanoacrylate glue preoperatively to aid in hemostasis. High-resolution CT/MRI or dynamic contrast-enhanced MRA (TRICKS) may be useful for the surgical planning of complex lesions.
Overall 5-year survival of orbital hemangiopericytomas has been reported as 89%. Local recurrences are relatively common, at 4-7% at 1 year and 15-33% at 5 years. A multidisciplinary management approach in conjunction with the primary care physician and oncologist is recommended. Metastases are relatively rare in orbital, subconjunctival and lacrimal hemangiopericytomas; however, metastases have been reported in the lung, liver, bone and mediastinum.
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