M1A disease is a recent concept appearing in the 7th TNM classification of lung cancer. M1A encompasses two different entities, malignant pleural or pericardial effusions and separate tumor nodules in the contralateral lung, who constitute very different diseases, with very different management and prognoses. On one hand, patients with pleural dissemination have extremely poor survival, with median and 5-year survivals of 4 months and 3.1%, respectively. Only selected patients whose limited pleural extension has been diagnosed at the time of thoracotomy and completely resected, may experience prolonged survival. On the other hand, recent progress in molecular biology still failed to establish whether a contralateral lesion is a second primary or a metastasis. These contralateral lesions are now gathered as multiple lung cancers in the surgical literature, and misleadingly classified as M1A disease in the TNM classification. Patients with contralateral nodules may experience prolonged survival after the surgical treatment of both localizations. Changing the staging by establishing the diagnosis of metastasis is probably an important issue warranting further biologic research, but according to current results this diagnosis must not in any case preclude surgery.
Keywords: M1A disease; metastatic pleural extension; multiple lung cancer; non-small cell lung cancer; surgery.
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