Problems in diagnosing cancers from their symptoms

The symptoms and signs of cancer are extremely diverse, depending on where in the body the tumours are growing. There are no characteristic signs and symptoms that are only due to cancers, because their effects resemble many other diseases. Some symptoms are local, affecting only the tissue or organ containing the original tumour; for example, a persistent cough may be a symptom of cancer in the lungs. Some cancers may have widespread effects all over the body; for example, cancer in the pancreas can alter the production of insulin and glucagon (Study Session 2), causing disruption to the patient's energy supply from glucose in the diet, affecting all body functions.

There are many other examples of the difficulty in distinguishing between a cancer and another disease. For instance, cancer of the ovaries frequently leads to a lot of fluid collecting in the abdomen, causing swelling and pain which can be confused with intestinal obstruction (described in Study Session 8 later in this Module). Fluid and swelling in the abdomen presses up against the diaphragm (the muscular wall separating the lung cavity from the abdomen), restricting the ability of the person to breathe deeply. This causes the symptom of breathlessness, which can easily be confused with chronic obstructive pulmonary disease or bronchial asthma (described in Study Session 4).