Primary signet-ring cell carcinoma of the lung treated with crizotinib: A case report.

Primary signet-ring cell adenocarcinoma (SRCA) of the lung is an extremely rare subtype of lung adenocarcinoma with a poor prognosis. The presence of an SRC component is considered to be a prominent clinicopathological characteristic of EML4-ALK-positive non-small cell lung cancer (NSCLC). Crizotinib, an anaplastic lymphoma kinase inhibitor, has been approved for the treatment of EML4-ALK NSCLC by previous studies, but its effect on SRCA, an extremely rare subtype of lung adenocarcinoma, has yet to be elucidated.