Uncommon Orbital Lesions: Solitary Fibrous Tumors

Etiology

• Rare spindle cell tumor that arises from mesenchymal cells
• Typically found in the pleura, pericardium, peritoneum, liver, and kidneys, and only rarely in the head and neck; between 1994 and 2018, only 90 cases of orbital solitary fibrous tumor reported (Shen, Cancer Manag Res 2018)
• Can have endothelial differentiation and significant vascularity
• Typically behaves in a benign manner, but malignancy, recurrence, invasion, and metastasis can occur (Bernardini, Ophthalmology 2003)

Epidemiology

(Le, Orbit. 2014)

• Most common in adults 30–50 years old
• Can occur at any age; children as young as 5 have been reported (Blandamura, J Clin Pathol 2014)
• 90 cases of orbital solitary fibrous tumors (SFT) reported in the literature
• Slight male predilection

History

• Slowly progressive, painless proptosis (most common sign)
• Decreased vision
• Diplopia
• Previous history of orbital tumor

Clinical features

Figure 1. Frontal photo demonstrating right inferolateral globe dystopia, exophthalmos, and exotropia from solitary fibrous tumor.

Figure 2. Coronal MRI of patient in Figure 1.

Figure 3. Axial MRI of same patient. Image courtesy Anne Barmettler, MD.

Figure 4. Frontal photo of patient with right orbital solitary fibrous tumor causing ptosis, edema, and erythema.

• Proptosis
• Dystopia
• Lid swelling
• Decreased motility
• Ptosis
• Chemosis
• Loss of vision due to optic neuropathy are rare.
• Typically occurs superiorly, but can occur anywhere in the orbit
• 20% superomedial
• 15% medial
• 13% superotemporal
• 7% inferotemporal

Testing

• Evaluation of motility, vision, pupils, Hertel exophthalmometry
• CT scan (Dalley, Radiol Clin North Am 1999; Kim, AJNR Am J Neuroradiol 2008)
• Typically well circumscribed, but can be irregular
• Nonencapsulated
• Bone erosion is rare, but can occur with longstanding, recurrent, or aggressive lesions
• 25% have focal areas of calcification
• Significant feeder vessels and enhancement is seen with intravenous contrast

Figure 5. Axial CT of patient from Figure 4 showing lateral orbital mass. Image courtesy Greg Griepentrog, MD.

• MRI (Dalley, Radiol Clin North Am 1999; Kim, AJNR Am J Neuroradiol 2008)
• T1
• Heterogenous
• Isointense to muscle, hypointense to fat
• T2
• Hypointense to muscle, hyperintense to fat
• Areas of signal void due to large blood vessels
• Homogenous enhancement with gadolinium
• Echography (Johnson, Ophthal Plast Reconstr Surg 2003)
• Firm, low-to-medium internal reflectivity, regular internal structure, moderate sound attenuation, vascularity
• Histopathology
• Well circumscribed
• Dense spindle cells with scant cytoplasm
• “Patternless pattern” consisting of thick bands of collagen with areas of hyper- and hypocellularity, storiform and fascicular formations, and neural-type palisades (Heathcote, Can J Ophthalmol 1997)
• Bands of collagen are a distinguishing feature not found in fibrous histiocytoma or hemgiopericytoma (Tam, Orbit 2008).
• Vascular channels
• Recurrent lesions can have mitotic figures, nuclear pleomorphism, and necrosis.
• Immunohistochemical staining
• Vimentin
• CD34 strongly positive in 90%–100% (Westra, Am J Surg Pathol 1994)
• Hemangiopericytomas by contrast tend to be weakly positive.
• Other tumors on the differential do not exhibit CD34 activity.
• Useful in differentiating from fibrous histiocytoma and hemangiopericytoma
• Malignant SFTs have been reported to lack reactivity (Girnita, Acta Ophthalmol. 2009)
• Malignant behavior is suggested by hypercellularity, tumors larger than 5 cm, more than four mitotic figures per 10 high-power microscopic fields, and tissue necrosis (Shen 2018).

Risk factors

• Middle-aged adults

• Cavernous hemaniogoma
• Hemangiopericytoma
• Fibrous histiocytoma
• Schwannoma
• Glioma
• Meningioma
• Giant cell angiofibroma

Natural history

• Typically a benign lesion with a rare possibility of recurrence and malignant transformation

Medical therapy

Radiatiotherapy has been used in cases of malignant transformation following subtotal excision (Blandamura, J Clin Pathol 2014).

Surgery

Complete excision is the mainstay of treatment.

Surgery can be complicated by significant bleeding due to vascularity of the lesion.

Friable lesions and infiltrative borders can lead to subtotal excision.

• Blandamura et al. reported 4 cases of subtotal excision where 3 of 4 patients did well postoperatively; however, 1 had a malignant transformation.
• Close follow-up could be considered in cases of residual disease with nonaggressive features on histopathology.

Preventing and managing treatment complications

• Surgical complication: risk of intraoperative bleeding due to lesion vascularity

(Le, Orbit 2014)

• Recurrence:
• 24% following excision
• Tend to be more invasive following recurrence; however, only 5% of reported recurrences were malignant
• Local invasion: Although rare, intracranial extension has been reported (Young, Ophthal Plast Reconstr Surg 2011).
• Malignant transformation: only 4 reported cases of malignant orbital SFTs
• Metastasis: only 1 reported case of distant metastasis

Patients need to be aware of the possibility of recurrence, malignancy and metastasis.

In addition to being followed closely, they need to note worsening vision, diplopia, or proptosis.

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