Metastatic plexopathy has been documented in the literature. Lung carcinoma, breast carcinoma, and non-Hodgkin lymphoma have been shown to metastasize to the brachial plexus. In most of these cases, the tumors are found to spread from the surrounding axillary lymph nodes to the neuronal structures. The clinical features are pain in the upper shoulder girdle and the medial aspect of the forearm. The lower plexus is more commonly involved and may be associated with Horner syndrome.
Direct infiltration is by far the most common cause of neoplastic plexopathy.
The other common presentation in this category is Pancoast, in which tumor invades the nerve roots as they exit the paravertebral space close to the apex of the lung. Isolated cranial neuropathy has been reported but is uncommon. In most cases, they are associated with carcinomatous meningitis. Clinically, it affects several levels of the neuraxis. The most common symptoms are headache, mental status changes, seizures, ataxia, nonobstructive hydrocephalus, and painful radiculopathy.