Horner's syndrome in a patient with diffuse malignant pleural mesothelioma

A 63-year-old man was admitted to our hospital because of left back pain and dysesthesia in his left arm. On physical examination, the patient had ptosis, myosis, and anhydrosis on the left side, suggesting Horner's syndrome. A chest computed tomographic scan disclosed a mass lesion adjoining to the left posterior mediastinum. Although the mass lesion showed a slight decrease in size after the systemic administration of corticosteroids, no further improvement was obtained. Open chest examination revealed extended thickening of the parietal pleura with massive involvement of the upper thoracic sympathetic trunk. The diagnosis was malignant mesothelioma of sarcomatous type. Horner's syndrome is a rare but possible complication in the clinical course of malignant pleural mesothelioma.