Читать книгу The Cancer Directory - Dr. Daniel Rosy - Страница 85

With different types of cancer, there are differences in how quickly metastatic spread can take place. But it also depends on the individual who has it (more about this later).

There are two types of tumour – benign or malignant. Benign tumours are usually localized and do not spread. They are often enclosed in a clear capsule – a rim of normal tissue – which demarcates the limits of the abnormal cells. These tumours may be detected because, as they grow, they press on other structures in the body such as blood vessels or the intestines. In contrast, malignant tumours are virtually never encapsulated, but erode adjacent tissues by extending crab-like infiltrations in the body in all directions.

Most cancers do not spread completely haphazardly – certain tumours have favoured sites of metastases. Prostate cancer, for example, tends to spread to the bones, often the spine or pelvis. Breast cancer usually goes first to the lymph nodes, but then favours the liver, bones and lungs. Colon cancer spreads first to the liver, following the blood flow from the colon to the liver.

Cancer cells produce chemical factors that enable them to grow as a group, and we are only just beginning to understand the growth factors involved in sustaining cancer cell growth. In future, we may be able to devise anti-cancer drugs that can block these growth factors.