Metastatic mammary carcinoma to the orbit masquerading as maxillary sinusitis.

INTRODUCTION: We report on a case of isolated metastatic breast cancer to the medial rectus muscle. This entity is exceedingly rare.

CASE: A 44-year-old female with a history of breast cancer presented with unilateral maxillary symptoms and was treated for sinusitis. Over time, she developed ocular pain, diplopia, blurred vision and eventually complete adduction deficit.

RESULTS: T1-weighted magnetic resonance imaging revealed a medial rectus lesion. Biopsy via transnasal transorbital endoscopic approach revealed metastatic mammary carcinoma.

DISCUSSION: Metastatic disease to the orbit should be considered in the differential diagnosis of refractory maxillary sinus pain in patients with a known underlying malignancy.