Tumours and cysts of the mediastinum.

Most mediastinal tumours and cysts follow a definite pattern due to their site of origin and the effect upon neighbouring structures of their enlargement. A small number deviate from the usual picture, and it was felt that the examination of a large series might disclose enough of these variants to enable some contribution to be made to the basic aetiology and diagnosis of these tumours. The present material consists of 332 cases. One hundred and sixty-six of these were investigated at the Liverpool Regional Thoracic Centre from 1941 to June, 1957, all completely verified cases being included. The other 166 cases were referred to the Tumour Registry of the Society of Thoracic Surgeons of Great Britain and Ireland between 1953 and April, 1957, by centres other than Liverpool. (The Liverpool cases referred to the Tumour Registry are included only in the first series.) The coincidence of these numbers is purely fortuitous. The Tumour Registry is selective and contains only part of the experience of British and Irish thoracic surgeons. This is evident when the percentage of thyroid tumours in the Tumour Registry series is compared with that in the Liverpool series. The diagnosis has usually been verified by excision, but sometimes by biopsy or aspiration.