The patient went on to have surgery.
MICROSCOPIC DESCRIPTION: Paraffin sections show collections of markedly atypical cells within oedematous and haemorrhagic brain parenchyma. These have irregularly shaped enlarged hyperchromatic nuclei, some with multiple nuclei and a variable amount of pale and vacuolated cytoplasm. The tumour cells are AE1/3, CAM5.2, CK7, CK19 and EMA positive. They are BHCG, c-kit, PLAP, AFP, tyrosinase, GFAP, nestin and TTF-1 negative. The features are consistent with metastatic choriocarcinoma.
FINAL DIAGNOSIS: Metastatic choriocarcinoma.