As regards the previous findings, primary tumors of the bone and pleura, as well as metastasis, are considered the main differentials for pancoast tumor.

Pancoast tumors originate from the lung seen at the apical pleuropulmonary groove (superior sulcus). By direct extension, they invade the lower trunks of the brachial plexus, intercostal nerves, related ribs, and vertebrae. Almost 95% of pancoast tumors are non–small cell carcinomas.