The patient had a prior history of lung cancer (adenocarcinoma) and went on to have surgery.

HISTOLOGY

MICROSCOPIC DESCRIPTION: The sections show a densely hypercellular tumor. Tumor cells have pleomorphic large vesicular nuclei many with conspicuous nuclei and a variable amount of pale cytoplasm and are arranged in solid aggregates. Frequent mitotic figures are identified and there is extensive tumor necrosis. Tumor is sharply demarcated from adjacent gliotic brain parenchyma. Immunohistochemistry shows positive staining with CK7 and BER-EP4. The tumor cells are TTF-1 and Napsin-A negative.

FINAL DIAGNOSIS: Metastatic undifferentiated non small cell carcinoma with features most consistent with an origin from lung.