Spread of tumour

Tumours may spread by:

♦ Local invasion

♦ Lymphatic and vascular channels

♦ Transcoelomic dissemination

Local spread may affect clinical presentation, staging, management, and prognosis. For example, a tumour in the apex of a lung (Pancoast tumour) may spread into the chest wall and into the brachial plexus, causing characteristic pain and neurological deficit. Where tumours abut tissue planes, imaging will often not indicate if the tumour has crossed such a plane. Pleural involvement by a peripheral lung carcinoma, for instance, will only be apparent at operation.

Transcoelomic spread is often seen in colorectal and ovarian carcinomas. Neither CT nor MR are good at showing peritoneal plaque disease, although both can readily demonstrate ascitic fluid and bulk of a tumour. While imaging may suggest that ascites is due to peritoneal disease, cytological proof will be necessary.

Tumours may show characteristic spread via lymphatics e.g. bronchial carcinoma to mediastinal nodes, melanoma to regional nodes, and testicular tumours to para-aortic nodes. Other tumours (e.g. lung and breast carcinomas) spread by haematogenous means to the liver, brain, bone, lung, and adrenal glands. The liver is a favourite site for spread from primary tumours in the gastrointestinal tract via the portal venous system. It acts as a venous filter with tumour emboli lodging and growing in the capillary bed.

Contrast-enhanced CT will detect 90% of metastases greater than 1 cm, although solitary lesions require biopsy to confirm their nature.

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