MICROSCOPIC DESCRIPTION: Sections show a well circumscribed malignant spindle cell tumour with areas of geographic necrosis. Tumour cells contain elongate, oval vesicular nuclei, prominent nucleoli and abundant eosinophilic cytoplasm. Frequent mitoses are observed (>20/10hpf). Tumour cells are set within a dense sclerotic stroma. Scattered thin and thick walled blood vessels are present. No heterologous elements are seen. Immunohistochemical results show tumour cells stain:
Positive: CD99, CKAE1/3, CAM5.2, EMA focal, CD31 focal, GATA3 focal, Calretinin focal
Negative: CD34, BCL2, SMA, Desmin, cKIT, DOG1, S100, SOX10, WT1, p40, CK7, CK20, CDX2, TTF1, Mesothelin, AFP, HepPar1
DIAGNOSIS: Brain tumour: Undifferentiated malignant spindle cell tumour of uncertain lineage - further immunohistochemical stains to follow.