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Please respond to the following with TRUE or FALSE.
Differential diagnosis:
Discussion
Orbital metastases are an uncommon etiology of orbital mass that are seen in 2-3% of cancers. They are predominantly unilateral and can go anywhere in the orbit. Orbital metastases account for 10% of orbital neoplasms, and breast and lung cancers combined account for 50% of cases. They represent 7% of cases of extraocular muscle enlargement, and 10% demonstrate an indeterminate primary after systemic evaluation. The average age of incidence is 61, and are more common in women than men. Some studies have suggested an increasing prevalence, but that may reflect improved long-term survival in cancer patients.
Patients may present with pain, proptosis, ptosis, diplopia, visual impairment/blurred vision, or palpable lid mass. Orbital metastases are associated with a high hematogenous metastatic burden. In terms of primary malignancy, breast is the most common (28.5 - 58.8%), followed by lung (8-12 %), unknown (11%), prostate (8.3%), melanoma (5.2%), gastrointestinal (4.4%), renal (3.2%), and squamous cell (2.0%). The etiology is age dependent, with adults most commonly presenting with breast, lung, prostate, and melanoma, and children more commonly presenting with neuroblastoma, rhabdomyosarcoma, or Ewing sarcoma.
Natural history depends on the primary malignancy, but outcome is almost universally poor. Average post-detection survival is approximately 9 months. Therapy is usually palliative, with the goal of prolonging function and comfort. Surgery is attempted in the rare case of well-circumscribed lesions, with enucleation usually unhelpful. Orbital radiation is the mainstay therapy, with 20-40 Gy administered over 2-4 weeks. Systemic therapy with chemotherapy or hormone therapy is often employed, with agents specific to the primary malignancy. Topical therapy (such as artificial tears) may be used to manage side effects of radiation or chemotherapy.
Radiologic overview of the diagnosis:
In terms of radiologic evaluation, CT with intravenous contrast is the first line modality, providing both soft tissue and bone detail. The majority of retrobulbar metastases are extraconal at first, but many involve the intraconal compartment as they grow. They are typically iso dense to hyper dense, and may enhance. The frequently show boney involvement. CT is nonspecific for histologic findings, but the combination of exophthalmos and infiltrating retrobulbar mass is characteristic for scirrhous breast carcinoma. Most metastatic lesions will progress to diffuse lesions, although thyroid, carcinoid, and renal cell carcinoma may remain discrete nodules. Breast cancer tends to metastasize directly to orbital fat, whereas prostate has a propensity to start as orbital bone metastases with secondary involvement of the orbital fat. Isolated enlargement of the lateral rectus muscle also favors metastasis or orbital pseudotumor over Graves. In children, rhabdomyosarcoma tends to have preseptal extension, whereas metastatic neuroblastoma does not. However, metastatic neuroblastoma tends to have a higher density.
MRI demonstrates improved soft tissue evaluation, and most metastases demonstrate T2 prolongation with or without enhancement.
Radiographs are insensitive, and may show destructive bone changes in advanced cases. Ultrasound does not have a role in widespread clinical practice.
Key points:
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