Orbital Solitary Fibrous Tumor

What is Orbital Solitary Fibrous Tumor?

Solitary fibrous tumors (SFTs) are a rare type of slow-growing tumor that develops from a particular type of cells called fibroblasts involved in the formation of body tissues. They were previously grouped under a broader category of tumors known as hemangiopericytomas. Despite being initially found in the lining of the lungs, which is referred to as the pleura, over time, SFTs have been recognized in various other parts of the body, including the protective lining of the abdomen, liver, middle of the chest, upper airway, kidney, adrenal gland, bladder, prostate, area around the eye, nose, structures adjacent to the nose, and other areas in the head and neck.

An analysis of a large group of patients with SFTs that were not located in the protective layers of the brain showed that these tumors can appear in several areas of the body: 31% in the abdominal cavity, 29% in the arms and legs, 22% in the lung linings, 11% in the trunk, and 7% in other sites, which also includes the head and neck, but not the protective layers of the brain.

SFTs in the region around the eye, also known as orbital SFTs, were first reported in 1994. These types of tumors can be difficult to diagnose because they share similarities with other growths in the eye region. Although they seldom spread to other parts of the body, the preferred course of treatment is complete surgical removal. Patients with an orbital SFT generally display vague symptoms such as slow-growing one-sided swelling of the eyelid, eyeball or area around the eye, a bulging eye, swelling, or a mass that can be felt by touch.

What Causes Orbital Solitary Fibrous Tumor?

Solitary fibrous tumors, or SFTs, were initially believed to be a type of tumor called mesothelial tumors because they mostly seem to originate from places like the lining around your lungs or heart. The very first SFT was described in 1931 and was thought to be a very specific kind of mesothelioma. However, as time passed, SFTs have been found in different parts of the body outside of these linings. These include the lungs, liver, thyroid, nasal sinuses, and even the area around the eye (the orbit).

Doctors think that these tumors outside of these linings might actually come from a different type of tissue, perhaps something similar to the fibroblasts, which are cells that help wound healing. Other possible sources might include specific types of cells that exist in nerves, skin, or in the walls of your blood vessels.

The exact reasons why SFTs occur in the orbit, or the area around the eye, are still not completely understood. However, scientists have found that these tumors look a certain way under an electron microscope and show intense results when tested with specific markers (CD34 and vimentin). These findings suggest that these tumors are similar to a type of cells known as fibroblasts. In addition, current studies suggest that unusual changes in how cells differentiate, or form, together with gene mutations, could have a part in the development of these types of tumors.

Risk Factors and Frequency for Orbital Solitary Fibrous Tumor

Solitary fibrous tumors (SFTs) can occur anywhere in the body, but about 20% of them are found in the head and neck. SFTs that occur in the eye socket, or orbital SFTs, are quite rare, making up less than 1% of all eye socket tumors. But when it comes to tumours not found in the chest, SFTs in the orbit or extremities are the most common. Men and women have an equal chance of getting an orbital SFT. While a few cases have been found in children as young as 5, most are found in adults aged 20 to 70, with the average age at diagnosis being 40.

Not as many people with SFTs in the chest lining, or pleural SFTs, develop related conditions, such as hypertrophic osteoarthropathy (HOA). HOA, a condition causing bone and joint pain, is more common than low blood sugar caused by cancer, but might be underdiagnosed in people with SFT. Other possible effects of SFT include low blood glucose, growth hormone, and insulin-like growth factor I or III levels. However, there have been no reported instances of these resulting conditions in patients with orbital SFTs so far.

Signs and Symptoms of Orbital Solitary Fibrous Tumor

Orbital Solitary Fibrous Tumors (SFTs) usually present as a slow-growing and painless swelling of the eye over months and even years. The most common issue seen in individuals with an orbital SFT is proptosis, which is the protrusion of the eyeball from the socket. The optic nerve, which plays a vital role in vision, is rarely affected. However, people may still experience changes in vision, pupil reactions, and visual fields. Also, patients may report seeing double, teary eyes, and swelling on the eyelid. The tumor’s growth can also interfere with the movement of the eyeball, leading to double vision. This is particularly common in tumors located in the front part of the eye. One critical step in determining if a person has an orbital SFT is measuring the degree of eye bulging using an instrument called an exophthalmometer.

The table below summarizes possible signs or symptoms and their corresponding likely cause relating to Orbital Solitary Fibrous Tumors:

• Decreased visual acuity (clarity of vision): Likely due to pressure on optic nerve (Compressive optic neuropathy)
• Dryness and ocular surface disease: Mass effect with or without nerve compression
• Diplopia (Double Vision): Likely due to the mass of the tumor impacting the eyeball (Mass effect with globe displacement or adhesion)
• Ptosis (Drooping of the upper eyelid): Likely due to the mass of the tumor pressing on nerves (Mass effect with or without nerve compression)
• Gaze-evoked amaurosis (Loss of vision when looking in certain directions): Likely due to the mass of the tumor compressing the optic nerve when the eye is in certain positions (Gaze-dependent optic nerve compression)
• Eyelid edema (Swelling): Likely due to the body’s inflammatory response to the tumor
• Proptosis (Eye bulging): Likely due to the mass of the tumor pushing the eyeball forward (Anterior globe displacement due to mass effect)
• Dystopia (Abnormal positioning of the eyeball): Likely due to the mass of the tumor moving the eyeball up, down, or sideways (Vertical or horizontal globe displacement due to mass effect)

Testing for Orbital Solitary Fibrous Tumor

Imaging is crucial in diagnosing orbital SFTs, a type of uncommon eye tumor. These tumors exist in various parts of the eye, but they most commonly appear in parts of the eye called the extraconal, among the ocular adnexa. The ocular adnexa consist of structures around the eyeball, including the tear glands, tear sac, or eyelid. Just like SFTs in other body parts, these ocular tumors exhibit STAT6 expression, a kind of protein in cellular functions.

To visualize these orbital SFTs, doctors use imaging scans like Computed Tomography (CT) or Magnetic Resonance Imaging (MRI). These tumors usually show up as well-defined tissue masses, sometimes with deposits called calcifications. Long-standing tumors can cause changes in the eye’s bony structure, although they don’t usually cause the destructive damage typically seen in malignant, or cancerous, tumors. These orbital SFTs become more visible, or “enhance,” when contrast dyes are injected during CT or MRI scans. Aggressive types of SFTs are more likely to show uneven enhancement than less severe types, after this injection.

The level of enhancement these tumors show is influenced by the blood supply to the tumor, leakiness of their blood vessels, and how quickly your kidneys can remove the contrast dye from your body. On the technical side, orbital SFTs typically appear as normal intensity (“isointense”) on T1-weighted MRI pictures and normal to less intense (“hypointense”) on T2-weighted ones, indicating the presence of a high collagen content in fibrous tissue. However, T2 pictures may show irregular brighter signals, which could suggest recent bleeding, cystic changes, or newly formed scar tissue inside the tumor. If an MRI includes the use of a contrast agent called gadolinium, these tumors typically show strong enhancement, especially those with a good blood supply.

Treatment Options for Orbital Solitary Fibrous Tumor

Orbital SFTs, a type of tumor located in the eye socket (or orbit), are typically treated by surgical removal. This is mainly due to their tendency to come back and potentially turn into malignant (cancerous) tumors if they are not fully removed. Sometimes, more intensive surgery (known as exenteration) may be needed in case of spreading malignant tumors, as both radiotherapy (using radiation to kill cancer cells) and chemotherapy (drugs to kill cancer cells) have limited effects on these tumors.

To make the surgery less complicated and time-consuming, doctors may also perform preoperative embolization. This procedure shrinks the tumor size by blocking its blood supply, thus reducing bleeding during surgery. Different materials like liquids, particles, or tiny coils can be used for this purpose.

There are several surgical techniques that doctors can use to remove these orbital tumors. The choice of the technique generally depends on the size and location of the tumor. One of these techniques is the fronto-orbital or pteronial approach. It is used mainly for tumors that involve the optic canal (the pathway for the optic nerve) or located within the eye socket at a region called the apex.

Doctors may also use a device known as the ultrasonic aspirator system, also known as SONO-PET, during surgery. This device breaks down tumor tissue, making it easier to remove, while also cleaning the surgical area by rinsing and suctioning.

Additionally, a treatment method called stereotactic radiosurgery may also be used for these tumors. This is a type of radiation therapy that focuses high-powered x-rays on a small, precise area. While there aren’t many studies about this method, it may serve as a good backup treatment after partial removal of the orbital SFTs or to treat the tumor if it comes back.

After the treatment, doctors prefer to keep a close watch on the patient’s condition through frequent check-ups and medical imaging to ensure the tumor does not come back.

What else can Orbital Solitary Fibrous Tumor be?

Orbital Solitary Fibrous Tumours (SFTs) are a condition that could be confused with other issues that cause bulging eyes, such as:

• Schwannomas
• Hemangiomas (common in infants, kids and adults)
• Fibrous histiocytomas
• Meningiomas
• Hemangiopericytomas

Initial growth spurts in capillary hemangiomas (most common in babies and children) usually occur within the first six months of life, after which, they start to shrink. On scanning, their appearance could be similar to orbital SFTs. However, they can be set apart by their invasive nature, bumpy and irregular margin, and brighter appearance on T2-weighted MRI scans.

Cavernous hemangiomas (more common in adults) often appear as clear oval-shaped masses on CT and MRI scans. They are usually found within the middle zone of the eye socket. These are differentiated from orbital SFTs by appearing brighter with fibrous separating walls on T2-weighted MRI scans and showing distinct enhancement features, like delayed contrast material pooling during dynamic investigations.

It’s important to differentiate between hemangiopericytomas and orbital SFTs, as the treatments for each vary and hemangiopericytomas tend to recur and spread. These are soft tissue tumours, which are well-encapsulated, highly vascular, and typically found near the sinuses, outside the orbital region. Orbital hemangiopericytomas are challenging to distinguish from orbital SFTs on imaging tests as they can show bone erosion or spread into adjacent tissues. Both T1 and T2-weighted MRI scans show these to have similar intensity to normal gray matter.

Other conditions such as orbital schwannoma, neurofibroma, fibrous histiocytoma, lymphoma, pseudotumor, and metastatic disease can also show faint contrast enhancement.

Below is a simplified version of the table that summarises the imaging findings for different orbital neoplasms:

• Orbital Solitary Fibrous Tumour: These are clearly outlined and show dense, uniform or uneven enhancement with potential areas of calcifications on scans.
• Schwannoma: These appear as dense, uniform out-of-eyeball masses that expand into bones without causing erosions.
• Cavernous hemangioma: These well-defined, uniform masses, slightly denser than muscles, are often found inside the eyeball.
• Fibrous histiocytoma: These well-defined soft tissue masses have similar intensity to muscles.
• Meningioma: They display diffuse, tubular thickening of the optic nerve sheath that enhances uniformly, often producing a characteristic “tram track” sign on sideways scans or a “doughnut” sign on front-view scans.
• Hemangiopericytoma: They appear as brightly enhancing soft tissue masses on CT, while having similar intensity to normal gray matter on T1- and T2-weighted MR images.

What to expect with Orbital Solitary Fibrous Tumor

The outlook for orbital SFTs, or tumors in the eye socket, varies based on several factors like the tumor’s size, location, how far it has spread, and the type of tissues that make up the tumor. If the entire tumor can be removed, the outlook is generally excellent. Around 75% of SFTs progress without causing major harm, while the other 25% may spread to the surrounding tissues, come back after they have been removed, or spread to other parts of the body.

Interestingly, even if an orbital SFT does come back, in 95% of the cases its composition is still benign or not cancerous. Also, up to 75% of tumors that, under microscope, look malignant or cancerous, show a non-aggressive behavior clinically. This means they don’t cause much damage.

A tumor can return anytime between 3 months to 40 years after it has been first removed. Moreover, if an orbital SFT affects important structures within the eye socket such as the optic nerve or major blood vessels, this can significantly impact the patient’s outlook. Tumors situated near these vital structures can be harder to completely remove, which can increase the risk of complications, potential functional impairment like vision loss or difficulty moving the eye, and the chances of the tumor coming back.

Possible Complications When Diagnosed with Orbital Solitary Fibrous Tumor

Space-occupying lesions can lead to complications due to their size and the pressure they exert on the surrounding tissues. The most common issue associated with large intraconal orbital SFTs (a type of tissue growth) is compressive optic neuropathy. Malignant orbital SFTs, which spread into surrounding tissues, may cause chronic pain, unusual sensations, and an eye condition known as glaucoma.

Surgery to remove an orbital mass does carry its own set of risks, including:

• Retrobulbar hemorrhage (bleeding behind the eye)
• Diplopia (double vision)
• Ptosis (dropping of the upper eyelid)
• Strabismus (eyes that don’t look in exactly the same direction at the same time)
• Reduced vision
• Blindness
• Postoperative inflammation (swelling after surgery)
• Cellulitis (a serious skin infection)
• Inadequate tumor excision (not all of the tumor is removed)

If the tumor is not fully removed, recurrence or malignant transformation (the tumor becoming cancerous) may occur. Hence, close monitoring after orbital surgery is crucial.

Recovery from Orbital Solitary Fibrous Tumor

Patients who have had their tumors completely removed may find regular check-ups beneficial. On the other hand, those whose tumors weren’t entirely removed should have check-ups more often, along with regular scans to watch for any return of the tumor. Long-term monitoring can help spot if the tumor starts to grow back or spread, ensuring quick action can be taken if needed.

Preventing Orbital Solitary Fibrous Tumor

People diagnosed with orbital SFTs, or tumors in the eye socket, need to fully understand the importance of regular check-ups after surgery. This is to keep an eye out for any signs that the disease might be returning. If the tumour is small and not causing any symptoms, some patients may choose to be monitored through repeated health checks and medical imaging tests rather than undergoing immediate surgery.