While advanced cancer may cause pain, it is not always the first symptom. Roughly, cancer symptoms can be divided into three groups:
Local symptoms: unusual swelling (tumor in Latin means swelling), hemorrhage (bleeding), ulceration or jaundice.
Symptoms of metastasis (spreading): enlarged lymph nodes, cough and hemoptysis, hepatomegaly (enlarged liver), bone pain, fracture of affected bones and neurological symptoms.
Systemic symptoms: weight loss, poor appetite and cachexia, 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 has a substantial differential diagnosis (it may be associated with unrelated diseases). Often, cancer is an unexpected finding during investigation for much more common symptoms, while others are diagnosed through screening (see below).
Types of Cancer
Cancers originate within a single cell. Hence, cancers can be classified by the type of cell in which it originates and by the location of the cell.
Carcinomas originate in epithelial cells, e.g. skin, digestive tract or glands. Leukemia starts in the bone marrow stem cells. Lymphoma is a cancer originating in lymphatic tissue. Melanoma arises in melanocytes. Sarcoma begins in the connective tissue of bone or muscle. Teratoma begins within germ cells.
Adult cancers usually form in epithelial tissues and are believed often to be the result of a long biological process related to the interaction of exogenous exposures with genetic and other endogenous characteristics among susceptible people.
Examples include: bladder carcinoma, blood (and bone marrow) – hematological malignancies, leukemia, lymphoma, Hodgkin’s disease, non-Hodgkin’s lymphoma, multiple myeloma, brain tumor, breast cancer, cervical cancer, colorectal cancer – in the colon, rectum, anus, or appendix, esophageal cancer, endometrial cancer – in the uterus, hepatocellular carcinoma – in the liver, gastrointestinal stromal tumor (GIST), laryngeal cancer, lung cancer, mesothelioma – in the pleura or pericardium, oral cancer, osteosarcoma – in bones, ovarian cancer, pancreatic cancer, prostate cancer, renal cell carcinoma – in the kidneys, rhabdomyosarcoma – in muscles, skin cancer (including benign moles and dysplastic nevi), stomach cancer, testicular cancer, and thyroid cancer.
Cancer can also occur in young children, particularly infants. Here, the aberrant genetic processes that fail to safeguard against the clonal proliferation of cells with unregulated growth potential occur very early in life and progress very quickly.
The age of peak incidence of cancer in children occurs during the first year of life. Neuroblastoma is the most common infant malignancy, followed by the leukemias and the central nervous system cancers. Female infants and male infants have essentially the same overall cancer incidence rates, but white infants have substantially higher cancer rates than black infants for most cancer types.
Relative survival for infants is very good for neuroblastoma, Wilms’ tumor and retinoblastoma, but not for most other types of cancer. Childhood cancers include, from most frequently occurring to least: Neuroblastoma, leukemia, central nervous system, retinoblastoma, Wilms’ tumor, germ cell, soft tissue sarcomas, hepatic, lymphomas, epithelial.
A biopsy leads to the definitive diagnosis of most malignancies. It requires the removal of cells and/or pieces of tissue for examination by a pathologist. The tissue diagnosis indicates the type of cell that is proliferating, its severity (degree of dysplasia), its extent and size, and – sometimes with help from cytogenetics and immunohistochemistry – prognostic and therapeutic determinants.
Biopsy can be curative if the whole lesion is removed; in this case, the borders of the sample are examined closely to see if all malignant tissue has truly been excised.
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.
Cancer screening is the widespread uses of tests to detect cancers in the population. It is often an inexpensive, noninvasive procedure. If signs of cancer are detected, more definitive and invasive followup tests are performed to confirm the diagnosis.
Screening for cancer can lead to earlier diagnosis. Early diagnosis may lead to extended life. A number of different screening tests have been developed. Colon 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 precancerous 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.
Breast cancers can be detected by breast self-examination and regular screening mammograms. Testicular self-examination – is recommended for men from the age of 15 years to detect testicular cancer. Prostate cancer can be screened for by a digital rectal exam along with annual prostate specific antigen blood testing.
Screening for cancer is controversial in cases when it is not yet known if this 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).
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.
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 an incidentaloma – a benign lesion that may be interpreted as a malignancy and be subjected to potentially dangerous investigations.