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Orbital metastasis

Dr Jan Frank Gerstenmaier and Dr Frank Gaillard et al.

Orbital metastasis is relatively uncommon, but some primary tumours do have a predilection to metastasise to the orbit.

This article concerns itself with extraocular metastases, rather than intraocular tumours or direct extension of tumours from neighbouring regions. For a discussion of intraocular metastases please refer to uveal metastases.

Epidemiology

Extraocular orbital metastases are uncommon, accounting for 2 - 11% of all orbital neoplasms, and significantly less common than uveal metastases, which outnumber orbital metastases by 8 to 1 ^1,3,6. The demographics of affected patients reflect the demographics of the primary tumours (see below).

Clinical presentation

In general patients with metastatic disease do not develop orbital metastases, being identified clinically in less than 1% of cases, although much more prevalent when autopsy series are carried out (thus many patients who die from metastatic disease have asymptomatic orbital deposits) ⁷.

In as many as 30-50% of patients who are symptomatic from orbital metastases (except for breast cancer metastases), orbital symptoms occur well before local symptoms form the primary tumour manifest, and as such are the first indication of advanced malignancy ^1,3,6.

Unlike primary orbital tumours which most frequently present with proptosis and / or visual loss, orbital metastases most commonly present with diplopia ¹. Pain is also frequently present.

Enophthalmos due to infiltration and desmoplasia is most frequently encountered with breast carcinoma metastases, although it may also be occasionally seen in adenocarcinoma form the gastrointestinal tract ⁴.

Diagnosis is often known, or widespread metastatic disease offers easier targets for biopsy. In cases where orbital metastases are isolated biopsy may be required to establish the diagnosis. This is usually performed as an open biopsy, to allow for adequate haemostasis ^1,3.

Pathology

Common tumours to metastasise to the orbit include ^1-6:

Radiographic features

In contrast to uveal metastases which are often bilateral (up to 25%), extraocular orbital metastases are usually unilateral (with the exception of neuroblastoma) ⁷, and only infrequently primarily involve the extraocular muscles (with the exception of melanoma) ⁷, although secondary involvement as the metastasis grows is common ^1-2. Thyroid and prostate metastases are frequently located in the bony margins of the orbit ⁷.

The superior lateral extraconal quadrant is most frequently involved although all parts of the orbit may be the site of metastatic deposit.

CT

CT appearances are variable. In most instances soft tissue attenuating material is identified, located in the extraconal compartment ⁶. The morphology is variable, ranging from well defined rounded lesions to diffusely infiltrating lesions ⁵.

In general enhancement is present. Bony destruction may also sometimes be seen, and careful assessment of the remainder of the scan essential in identifying additional deposits.

MRI

MRI appearances are similar to CT, but the greater contrast resolution of MRI makes it invaluable in the assessment of orbital masses.

Fat supressed T2 and post contrast T1 weighted images, with thin slice thickness and a reduced FOV is ideal, and should include the cavernous sinuses.

T1 : isointense to muscle ⁸
T2 : hyperintense to muscle, hypointense to fat
T1 C+ (GAD) : enhancement present but variable

Treatment and prognosis

Treatment is primarily with radiotherapy, typically with a total dose of 30 - 40Gy ¹. Depending on the tumour histology chemotherapy may also be useful. Surgery is usually limited to patients with isolated orbital involvement without an identifiable (or a previously treated) primary.

Unfortunately, the discovery of orbital metastases usually indicates advanced and widespread metastatic disease and prognosis is dismal with the majority of patients succumbing to their illness within a year (average time from diagnosis to death is 4 months) ⁷.