Tumor-to-tumor metastasis: lung adenocarcinoma metastasizing to intracranial benign meningioma as a first clinical manifestation, with literature review.

We report a case of lung adenocarcinoma metastasizing to intracranial meningioma as a first clinical manifestation. Surgeons should be aware of this rare lesion. A 70-year-old Chinese woman was admitted to our hospital with a complaint of progressive left hemiparesis, predominantly of the upper extremity, for 20 days. Computed tomography (CT) revealed a mass on the right side of the right occipital cerebral falx. The subsequent magnetic resonance imaging (MRI) showed an oval mass with equal intensity on T1 weighted imaging (WI) and heterogeneous equal intensity on T2 WI. Within the tumor, a low T1 signal lesion was moderately enhanced after enhanced scanning with a relative boundary. Neuroimaging indicated a meningioma and the patient underwent a total mass resection. Formalin-embedded sections demonstrated two histologically distinct tumors (meningioma and adenocarcinoma) simultaneously in the same lesion without an intermediate transitional zone. Meanwhile, immunohistochemical (IHC) staining showed two distinctly different immunophenotypes in these two tumors and indicated that the component of adenocarcinoma might be a metastasis from a primary lung cancer. Therefore, a subsequent pulmonary CT scan was performed and found a mass at the tip of the upper lobe of the right lung. Fine-needle aspiration biopsy demonstrated an adenocarcinoma. The primary lung adenocarcinoma shared similar histologic morphology with that of the intracranial metastatic site. The final diagnosis waslung adenocarcinoma metastasizing to intracranial benign meningioma. The patient died of heart failure 2 weeks after surgery.