Etiology

• Arises from mesenchymal cells in fascia, muscle, or other soft tissues
• Orbit is the most commonly affected periocular structure
• Conjunctiva and eyelids can also be involved.

Epidemiology

• Three main subtypes. based on clinical behavior
• Benign 63%
• Locally aggressive 26%
• Malignant 11%
• A rare tumor, however the most common mesenchymal tumor of the orbit
• Most common in adults 30–60 years old
• 3%–10% occur in pediatric population; can occur following external beam radiation for retinoblastoma (Shields, Ophthal Plast Reconstr Surg. 2001)
• Male = female
• Some authors have suggested that fibrous histiocytoma refers specifically to fibroblastic spindle cell tumors of the orbit with aggressive behavior and have advocated re-classifying more superficial, benign lesions as dermatofibromas (Tieger, Ophthal Plast Reconstr Surg. 2019).

History

• Decreased vision
• Progressive proptosis
• Diplopia
• Previous history of FH

Clinical features

• Proptosis
• Dystopia
• Lid swelling
• Loss of vision
• Afferent pupillary defect due to compressive optic neuropathy
• Decreased motility
• Ptosis
• Chemosis
• Ephiphora and dacryocystitis if there is extension into the lacrimal sac (Stefanyszyn, Ophthal Plast Reconstr Surg. 1994)
• Most commonly occur supranasally, however can occur anywhere in the orbit and periorbital sctructures
• FH reportedly can occur in the lacrimal gland (Bajaj, Ophthal Plast Reconstr Surg. 2007)

Testing

Evaluation of motility, vision, pupils, Hertel exophthalmometry

Computed tomography

• Typically well circumscribed, but can be irregular
• Similar in appearance to schwannomas or cavernous hemangiomas
• Bone erosion is rare, but can be seen in recurrences or malignant lesions.

Magnetic resonance imaging

• T1
• Heterogenous
• Isointesnse to slightly hyperintense to muscle, hypointense to fat
• T2: Collagenous regions appear hypointense, whereas cellular areas are hyperintense.
• Heterogenous enhancement with gadolinium

Positron emission tomography

• Useful in detecting metastases as well as deciphering a recurrence from post-surgical changes (Char, Orbit. 2000)

Histopathology

• Benign:
• Poorly defined margins
• Spindle-shaped fibroblasts with a storiform pattern
• Can have vascular areas that are indistinguishable from hemangiopericytomas
• Locally aggressive
• Infiltrative margins
• Hypercellular
• Mitotic figures
• Malignant
• Infiltrative margins
• Nuclear pleomorphisms
• Atypia
• Necrosis
• Multinucleated giant cells
• Immunohistochemical staining
• Vimentin
• Alpha-antitrypsin
• Factor XIIIA
• Smooth muscle actin
• CD68

Figure 1. Completely excised fibrous histiocytoma.

Risk factors

• Middle aged adults

• Cavernous hemangioma
• Hemangiopericytoma
• Schwannoma
• Solitary Fibrous tumor

Natural history

(Font, Hum Pathol. 1982.)

• 63% are benign, 26% are locally aggressive, and 11% are malignant.
• Recurrence:
• Benign: 31%
• Locally aggressive: 57%
• Malignant: 64%
• 10-year survival rates:
• Benign: 100%
• Locally aggressive: 92%
• Malignant: 23%

Medical therapy

• Radiation has been shown to be ineffective, and has even been reported to induce formation of malignant FH (Zhang, World J Surg Oncol. 2014; Shields, Ophthal Plast Reconstr Surg. 2001)
• Adjunctive chemotherapy

Surgery

• Local Excision for well-circumscribed lesions
• Locally invasive and malignant lesions often require a wide surgical excision.
• Malignant recurrences and aggressive lesions might require exenteration.

• Surgical complications depend on technique and are discussed in greater detail in reviews of surgery.
• Chemotherapy complications should be managed by an oncologist.

Disease-related complications

• Recurrence
• Local invasion
• Intracranial invasion (Ueda, Neurol Med Chir (Tokyo). 2003)
• Metastasis

Patient instructions

Follow closely for recurrent orbital signs including decreased vision, pain, proptosis, diplopia or a palpable mass.

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