Background: Horner syndrome is caused by a lesion affecting the sympathetic innervation of the lids and pupil. The most common factor producing the preganglionic Horner's syndrome is malignant tumors.
Methods: We report here a case of Horner syndrome in young women with the history of breast cancer. The patient underwent extensive neurological examinations, including MRI of head and neck, together with chest radiograph and CT thorax scan.
Results: Present radiographic methods revealed one-sided metastatic pleural effusion as a cause of sympathetic lesion.
Conclusion: Metastatic breast disease usually affects lungs, bone, liver, adrenals and skin, and it is highly unusual for ocular involvement to be the first sign of its existence. This report presents a rare case of pleural metastatic breast cancer causing Horner's syndrome/Pancoast syndrome without lung involvement.