A bronchogenic apical lung tumor may lead to the compression of which anatomical structure causing Horner's syndrome?

In the case of a bronchogenic apical lung tumor, particularly a Pancoast tumor, the compression of the sympathetic ganglion—in particular, the stellate ganglion—can lead to Horner's syndrome. Horner's syndrome is characterized by a triad of symptoms: ptosis (drooping of the eyelid), miosis (constricted pupils), and anhidrosis (lack of sweating) on the affected side of the face.

The sympathetic chain runs along the spine and innervates various structures, including those of the face and eye. When a tumor in the apex of the lung infiltrates or compresses nearby structures, it often affects the sympathetic pathways. This disruption interferes with the normal sympathetic signals that control eyelid elevation, pupil dilation, and sweating, resulting in the symptoms of Horner's syndrome.

Other anatomical structures listed, such as the vagus nerve, phrenic nerve, and recurrent laryngeal nerve, are associated with different symptoms and may be affected in cases of lung tumors, but they are not directly involved in the classic presentation of Horner's syndrome. Thus, the relationship between an apical lung tumor and the sympathetic ganglion directly leads to the neurological signs observed in Horner