Objective: To inform clinicians of a metastatic orbital neoplasm that frequently masquerades as an orbital inflammatory syndrome and to stimulate thought regarding this neoplasm's fundamental pathobiology specific to its orbital involvement. Design: Interventional case report and literature review. Participants: A 47-year-old woman with an acquired, bilateral, diffusely infiltrative orbital process is described. Intervention: The clinical and radiographic features of the patient's orbital process are reported. The review of two prior fine-needle aspiration biopsy specimens failed to reveal a diagnosis. Histopathologic examination of an open surgical biopsy specimen included standard light microscopy of frozen and formaldehyde-fixed, paraffin-embedded tissue. Results: Characteristic light microscopy findings suggested the diagnosis of metastatic lobular carcinoma of the breast. The patient refused all therapeutic intervention and died 9 months after orbitotomy. Conclusion: The presentation of breast carcinoma metastatic to the orbit as a bilateral infiltrative process is far more common than appreciated previously. Its rate of bilateral orbital involvement is 20%, whereas this rate for other adult neoplasms is much lower. The authors report an additional case, review the clinical features of previous case reports and series, and discuss aspects of the metastatic process. Breast carcinoma must be included in the differential diagnosis of infiltrative orbital processes encountered in adult female patients. When 'orbital pseudotumor' is detected in an adult female patient, a thorough medical history must be obtained and physical examination performed. If a possible primary breast carcinoma is indicated, one must be wary of metastatic disease, and a histologic orbital diagnosis is warranted. The frequency of orbital metastasis and bilateral orbital involvement of this neoplasm reinforces the possibility for organ-specific metastases.
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