Introduction

2% of all cancer deaths are due to brain tumours and 20% of paediatric neoplasms are in the CNS. Overall they account for 10%of all malignancies. Although it is difficult to generalize about all brain tumours, there are some common themes.

Classification

May be according to cell origin (see table) or histological grading by the World Health Organization (WHO):

1. ▪ Grade I: benign – growth is slow, cells are similar to normal cells and rarely spread into adjacent tissue; total excision can be curative.

2. ▪ Grade II: growth is slow but local spread possible. The tumour may ‘transform’ into higher grade.

3. ▪ Grade III: malignant – growth is quick, cells are pleomorphic with higher nuclear-to-cell ratio. Local spread likely.

4. ▪ Grade IV: highly malignant – aggressive growth with high mitotic rate.

Incidence

15–20 per 100 000 (primary and metastatic); 35 000 new cases per annum (USA).

20–30% of patients with systemic cancer will have brain metastases. Gliomas 7 per 100 000; meningiomas 1.2 per 100 000. Meningiomas and pituitary adenomas slightly commoner in women. 3.6 per 100 000 children per annum have a primary brain tumour, the second commonest cause of paediatric cancer after leukaemia, and the most prevalent solid tumour in children.

Aetiology

Unknown in most cases. Developmental abnormality: teratoma, dermoid, epidermoid, craniopharyngioma, chordoma, hamartoma, angioma, ganglioneuromas. Hereditary: haemangioblastoma in von Hippel-Lindau disease; meningiomas and acoustic neuromas in neurofibromatosis; astrocytomas in tuberous sclerosis. Immunosuppression: lymphoma. Radiation: meningioma, sarcoma, glioblastoma.

Symptoms

Benign slow growing tumours may reach large size without causing significant symptoms.