Effects of Tumours on the Individual

Most tumours require many years to form and grow to the point where they produce clinical manifestations. The signs and symptoms of benign or malignant tumours result for the most part from the local effects of either the primary tumour or its metastases. In some cases the primary tumour and the secondary metastases do not progress at the same pace, and in such an instance the primary tumour may manifest itself while the metastases do not cause symptoms and, as a result, go undetected for years.

In addition to local effects, malignant neoplasms produce systemic effects such as body wasting (cachexia) and a variety of clinical manifestations known as paraneoplastic syndromes. Both local and systemic effects are described in this section.

Benign and malignant tumours produce a number of effects in an individual that vary depending on the location of the tumour, the tumour's functional activity, and any acute events that occur as the tumour mass grows and evolves. Metastatic tumours (those that result from the spread of the primary tumour) can produce the same consequences. A tumour affects normal bodily functions by compressing, invading, and destroying normal tissues and also by producing substances that circulate in the bloodstream.

The location of the tumour will determine how fast it manifests itself. Tumours arising in the deep soft tissues of the retroperitoneal space (the area next to the kidney) can grow very large before they produce discomfort. On the other hand, a relatively small tumour in the lungs can produce partial obstruction of secondary airways and cause pneumonia, which can draw attention to the tumour at an early stage.

The expansive growth of benign neoplasms or the more destructive growth of malignant tumours may erode natural surfaces and lead to the development of ulcers and bleeding and create conditions that favour infection. Tumours of the colon are indicated when small quantities of blood are found in the stools through an occult blood test.

When abnormal tissue is growing in the midst of an organ, it is likely to interfere with the organ's function. Metastases growing in the adrenal gland, for instance, eventually can destroy the gland and produce adrenal insufficiency (a condition called Addison disease). Sometimes the clinical manifestations of a tumour result from a malfunction in the tumour cell itself. This is commonly seen in tumours of endocrine glands, whose cells produce excessive amounts of hormones. For example, benign tumours of the parathyroid gland (called parathyroid adenomas) oversecrete parathormone, which causes calcium levels in the blood to rise. Symptoms such as muscle weakness, fatigue, anorexia, nausea, and constipation are caused by the excess calcium levels.

In the life of a tumour, acute accidents can produce dramatic symptoms. For example, ovarian cysts can rupture and produce immediate and severe abdominal discomfort. Tumours growing freely in a cavity can become twisted and cut off the blood supply to the tumour. This interruption of blood flow can cause tissue death (infarction), which may result in internal bleeding and cause intense pain for the individual.