NCIt definition : Stage IVA includes: (Any T, Any N, M1a); (Any T, Any N, M1b). M1a: Tumor with separate
tumor nodule(s) in a contralateral lobe; tumor with pleural or pericardial nodules
or malignant pleural or pericardial effusion. Most pleural (pericardial) effusions
with lung cancer are a result of the tumor. In a few patients, however, multiple microscopic
examinations of pleural (pericardial) fluid are negative for tumor, and the fluid
is nonbloody and not an exudate. If these elements and clinical judgment dictate that
the effusion is not related to the tumor, the effusion should be excluded as a staging
descriptor. M1b: Tumor with single extrathoracic metastasis in a single organ (including
involvement of a single nonregional node). (AJCC 8th ed.);