TTF1 and lung cancer: The histological characteristics of pulmonary metastatic meningioma are the same as those of primary PM, but immunohistochemical testing shows that the tumor cells of pulmonary metastatic meningioma are positive for lung cancer-related markers such as CK7, creatinine kinase, and TTF-1, and can be distinguished from PM.13 There was no evidence of primary central nervous system tumors in our patient, and the tumor cells were negative for lung cancer-related markers, such as CK7, CK20, and TTF-1, which ruled out the possibility of pulmonary metastatic meningioma.