Some tumours show tendency to spread in certain tissues, such as lung cancer, breast cancer, thyroid and prostate cancer. Such behaviour can be explained by favourable environment for metastases growth and by circulatory conditions.
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Thus, malignant stomach tumours can be transferred into the intestine, from the kidneys to the bladder via urine, from one lung to another via bronchi, or from one part of the gland to another.
Tumours contain more water than normal tissues, the level of lipids is increased, particularly concentration of phosphatides (fatlike organic compounds) and cholesterol, and there is an increased amount of nucleic acids (meaning DNA and RNA), especially DNA. The amount of potassium is increased while the amount of sodium is reduced. Tumour tissue contains fewer vitamins than normal tissue. This is true for B-group of vitamins, vitamin A and vitamin E.
The success of today's therapies depends on whether it is conducted on time when the tumour is still local (non-metastatic) and how deep it is infiltrated into the tissue. Tumour tissues are more sensitive to radiation exposure and X-rays than normal tissues. Therefore, when exposed to radiation, tumour tissue will be destroyed much faster than healthy tissues in the surrounding area.
A return of the cancer at the site where it was surgically removed or seemingly destroyed by radiation is called tumour recurrence. Local recurrence means that the cancer has come back in the same place where it started. Regional recurrence means that the cancer has come back in the lymph nodes near the place where it started. Distant recurrence means the cancer has come back in another part of the body, some distance away from where it started. A benign tumour can also recur which is, however, a rare case.
Experience shows that despite the fact that some cancer cells are left after therapy relapse doesn't follow. It seems that in those cases the organism creates defence forces in contact with the tumour that act on cancer remains more successfully than on the whole previous tumour mass.
Recurrences five years after the therapy are rare. As a rule of thumb, recurrence occurs much sooner, sometimes after just a few weeks, more often after a few months and the new tumour is histologically (structurally) similar to the primary tumour. Early recurrence indicates that the possible metastases are developing quickly, and late recurrence indicates the opposite. Recurrent disease that develops after one year raises a hope into success of the repeated surgery. The occurrence of distant metastases means that the surgery was performed at time when the tumour was already inoperable.
A sarcoma is the type of cancer that develops from bones or muscles. There are two main types of sarcoma: soft tissue sarcomas and bone sarcomas. But sarcomas of uncertain type (when doctors can't determine the type of tissue where the cancer began) are also very common. Sarcomas are often misdiagnosed as sports injuries and when they are diagnosed they are often already quite large and difficult to remove surgically, and sometimes metastasized. Many subtypes of sarcomas are resistant to therapy.
Any unexplained lumps or growths have to be checked to rule out sarcoma. Each node in the breast should be considered potentially malignant until proven otherwise and each gastric ulcer should be carefully checked so that stomach cancer doesn't go overlooked. If inguinal hernia is rapidly worsening it should be checked is there a malignant process in the rectum or the bowel.
Any disruption in the menstrual cycle should be examined carefully regarding the possibility of cancer of genital organs. Bleeding from haemorrhoids should be examined to exclude the possibility of the existence of rectal and colon cancer. It is wrong to treat anaemia before detecting what is the cause because stomach or intestinal cancer or some other malignant process can be hidden behind it. Mouth cancer is sometimes diagnosed as a benign lesions (gaps in diagnostic biopsy), and malignant tumours of the throat, mouth, nose and ear occur with symptoms similar to symptoms of many other, innocuous illnesses so it's easy to misdiagnose them. ■