Cancer

Cancer is a class of diseases characterized by uncontrolled cell division and the ability of these cells to invade other tissues, either by direct growth into adjacent tissue (invasion) or by migration of cells to distant sites (metastasis). This unregulated growth is caused by damage to DNA, resulting in mutations to vital genes that control cell division, among other functions. One or more of these mutations, which can be inherited or acquired, can lead to uncontrolled cell division and tumor formation. Tumor ("swelling" in Latin) refers to any abnormal mass of tissue, but may be either malignant (cancerous) or benign (noncancerous). Only malignant tumors are capable of invading other tissues or metastasizing.

Diagnosing cancer

Most cancers are initially recognized either because signs or symptoms appear or through screening. Neither of these lead to a definitive diagnosis, which usually requires a biopsy. Some cancers are discovered accidentally during medical evaluation of an unrelated problem.

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Signs and symptoms

Roughly, cancer symptoms can be divided into three groups:

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• Local symptoms: unusual lumps or swelling (tumor), hemorrhage (bleeding), pain and/or ulceration. Compression of surrounding tissues may cause symptoms such as jaundice.
• Symptoms of metastasis (spreading): enlarged lymph nodes, cough and hemoptysis, hepatomegaly (enlarged liver), bone pain, fracture of affected bones and neurological symptoms. Although advanced cancer may cause pain, it is usually not the first symptom.
• Systemic symptoms: weight loss, poor appetite and cachexia (wasting), excessive sweating (night sweats), anemia and specific paraneoplastic phenomena, i.e. specific conditions that are due to an active cancer, such as thrombosis or hormonal changes.

Every single item in the above list can be caused by a variety of conditions (a list of which is referred to as the differential diagnosis). Cancer may be a common or uncommon cause of each item.

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Biopsy

A cancer may be suspected for a variety of reasons, but the definitive diagnosis of most malignancies must be confirmed by microscopic examination of the cancerous cells by a pathologist. The procedure of obtaining cells and/or pieces of tissue, and their examination, is referred to as a biopsy. The tissue diagnosis indicates the type of cell that is proliferating, its severity (degree of dysplasia), and its extent and size. Cytogenetic and immunohistochemistry tests may provide information about future behavior of the cancer (prognosis) and best treatment.

Related Topics:
Pathologist - Biopsy - Dysplasia - Cytogenetic - Immunohistochemistry

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All cancers can be cured if entirely removed, and sometimes this can be accomplished by the biopsy procedure. When the whole mass of abnormal tissue (the "lesion") is removed, the borders of the sample are examined closely to see if all malignant tissue has truly been excised. If the cancer has spread to other sites in the body (metastasis), complete surgical excision is impossible.

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The nature of the biopsy depends on the organ that is sampled. Many biopsies (such as those of the skin, breast or liver) can happen on an outpatient basis. Biopsies of other organs are performed under anesthesia and require surgery.

Related Topics:
Anesthesia - Surgery

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Screening

Cancer screening is a test to detect unsuspected cancers in the population. Screening tests suitable for large numbers of healthy people must be relatively affordable, safe, noninvasive procedures with acceptably low rates of false positive results. If signs of cancer are detected, more definitive and invasive followup tests are performed to confirm the diagnosis.

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Screening for cancer can lead to earlier diagnosis. Early diagnosis may lead to extended life. A number of different screening tests have been developed. Breast cancer screening can be done by breast self-examination. Screening by regular mammograms detects tumors even earlier than self-examination, and many countries use it to systematically screen all middle-aged women. Colorectal cancer can be detected through fecal occult blood testing and colonoscopy, which reduces both colon cancer incidence and mortality, presumably through the detection and removal of premalignant polyps. Similarly, cervical cytology testing (using the Pap smear) leads to the identification and excision of precancerous lesions. Over time, such testing has been followed by a dramatic reduction of cervical cancer incidence and mortality. Testicular self-examination is recommended for men beginning at the age of 15 years to detect testicular cancer. Prostate cancer can be screened for by a digital rectal exam along with prostate specific antigen (PSA) blood testing.

Related Topics:
Breast self-examination - Mammogram - Fecal occult blood test - Colonoscopy - Pap smear - Cervical cancer - Testicular self-examination - Testicular cancer - Digital rectal exam - Prostate specific antigen

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Screening for cancer is controversial in cases when it is not yet known if the test actually saves lives. The controversy arises when it is not clear if the benefits of screening outweigh the risks of follow-up diagnostic tests and cancer treatments. For example: when screening for prostate cancer, the PSA test may detect small cancers that would never become life threatening, but once detected will lead to treatment. This situation, called overdiagnosis, puts men at risk for complications from unnecessary treatment such as surgery or radiation. Followup procedures used to diagnose prostate cancer (prostate biopsy) may cause side effects, including bleeding and infection. Prostate cancer treatment may cause incontinence (inability to control urine flow) and erectile dysfunction (erections inadequate for intercourse). Similarly, for breast cancer, there have recently been criticisms that breast screening programs in some countries cause more problems than they solve. This is because screening of women in the general population will result in a large number of women with false positive results which require extensive follow-up investigations to exclude cancer, leading to having a high number-to-treat (or number-to-screen) to prevent or catch a single case of breast cancer early.

Related Topics:
Prostate cancer - PSA - Overdiagnosis - Prostate biopsy - Incontinence - Erectile dysfunction - Breast cancer

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Cervical cancer screening via the Pap smear has the best cost-benefit profile of all the forms of cancer screening from a public health perspective as, as a cancer, it has clear risk factors (sexual contact), the natural progression of cervical cancer is that it normally spreads slowly over a number of years therefore giving more time for the screening program to catch it early and the test itself is easy to perform and relatively cheap.

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For these reasons, it is important that the benefits and risks of diagnostic procedures and treatment be taken into account when considering whether to undertake cancer screening.

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Use of medical imaging to search for cancer in people without clear symptoms is similarly marred with problems. There is a significant risk of detection of what has been recently called an incidentaloma - a benign lesion that may be interpreted as a malignancy and be subjected to potentially dangerous investigations.

Related Topics:
Medical imaging - Incidentaloma

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