The patient already had a diagnosis of pathologically-proven lung adenocarcinoma from a biopsy six months ago, detailed below. Thus, cerebral metastases is the most likely diagnosis.
Microscopy: slides demonstrate infiltration of malignant neoplastic tissue composed of cells with high N/C ratio, pleomorphic hyperchromatic nuclei which cover alveolar spaces and also focally arrange occasionally in gland-like structure. There is also necrosis and vascular invasion.