Apical Malignant Pleural Mesothelioma Presenting as Horner's Syndrome: A Case Report.

Horner's syndrome is a well-recognized presentation of apical lung tumors, though rarely associated with malignant pleural mesothelioma (MPM), with only a few cases documented. We report the case of an 82-year-old man with persistent right-sided chest pain who developed unilateral right-sided ptosis, miosis and a sunken appearance to the eye, in the context of known asbestos exposure. Initial chest radiograph was reported as normal; however, subsequent computed tomography revealed an irregular right apical pleural mass measuring 7.0×4.3×7.5 cm. Biopsy with immunohistochemistry confirmed sarcomatoid MPM. This case report illustrates apical MPM mimicking Pancoast syndrome through compression of the upper thoracic sympathetic chain, resulting in preganglionic Horner's syndrome characterized by unilateral ptosis, miosis and anhidrosis ipsilateral to the lesion. In patients with known asbestos exposure, persistent respiratory symptoms should prompt a thorough investigation for MPM. The presence of preganglionic Horner's syndrome alone, or in combination with brachial plexopathy (arm pain, paresthesia or weakness, shoulder pain, or chest pain) - termed Pancoast syndrome, should heighten clinical suspicion of apical MPM. Cross-sectional imaging should be considered in all cases with a high index of suspicion, even if initial radiographs appear normal. Early recognition may facilitate timely diagnosis. This report contributes valuable insight to the limited literature documenting the association between apical MPM and pre-ganglionic Horner's syndrome.