A neoplasm or tumor is a cellular growth that is no longer responding to normal body controls. The cells continue to reproduce when there is no need. This excessive growth deprives other cells of nutrients. Many neoplasms lack any useful function because they consist of atypical (abnormal) or immature cells. The characteristics of each tumor depend on the specific type of cell from which the tumor arises, resulting in a unique appearance and growth pattern. The expanding mass also creates pressure on surrounding structures.
Nomenclature
Tumors are named according to a system. The root word, such as chondro, is the cell of origin, in this case, cartilage. Depending on the type of tissue where a tumor is located, the suffix indicates malignant tumors (carcinoma for epithelial tissue, sarcoma for connective tissue).
The suffix oma indicates a benign tumor. However, a number of neoplastic disorders have acquired unique names that are recognized in medical practice. Examples include Hodgkin's disease, Wilms' tumor, and leukemia. Oncology is the study of malignant tumors, otherwise known as cancer.
Characteristics of Benign and Malignant Tumors
The characteristics of specific tumors vary considerably. Depending on the cell of origin. Benign tumors usually consist of differentiated cells that reproduce at a higher than normal rate. The benign tumor is often encapsulated and expands but does not spread. Tissue damage results from compression of adjacent structures such as blood vessels. A benign tumor is not considered life-threatening unless it is in an area such as the brain where the pressure effect can become critical. By comparison, malignant tumors usually are made up of undifferentiated, nonfunctional cells.
The cells tend to reproduce more rapidly than normal. Tumor cells infiltrate or spread into surrounding tissue and easily break away to spread to other organs and tissues.
MALIGNANT TUMORS-CANCER
Pathophysiology
A tumor manifests as an enlarging space-occupying mass composed of more primitive cells. The normal organization, growth inhibition, contact controls, and cell-cell communication are
lost. Cell membranes, including surface antigens, are altered. The expanding mass compresses
nearby blood vessels, leading to necrosis and an area of inflammation around the tumor, increase-
ing pressure on surrounding structures. Malignant cells do not adhere to each other but often
break loose from the mass, infiltrating into adjacent tissue. Also, tumor cells often secrete enzymes such as collagenase, which break down protein or cells, adding to the destruction and facilitating the tumor's spread into adjacent tissue. Inflammation and the loss of normal cells lead to a progressive reduction in organ function.
As a tumor mass enlarges, the inner cells are frequently deprived of blood and nutrients and die. This necrosis can lead to more inflammation and infection at the site. Some cancer cells secrete growth factors, which stimulate angiogenesis, the development of new capillaries in the tumor, thus promoting tumor development.
Anti-angiogenesis factors have also been located and several new drugs are based on this blocking action. Tumor cells may "trap" nutrients, depriving normal cells, and preventing any tissue regeneration.
Some neoplasms develop very rapidly, whereas others remain in situ for a long time. In situ refers to neoplastic cells in a preinvasive stage of cancer that may persist for months or years. This condition offers an excellent opportunity for early diagnosis of cervical cancer and certain oral cancers.
Grading of tumors is based on the degree of differentiation of the malignant cells-a grade I tumor has well-differentiated cells similar to the original cells, whereas a grade IV tumor is undifferentiated with cells varying in size and shape (anaplasia); this type of tumor is considered highly malignant and likely to progress quickly.
Effects of Malignant Tumors
All health care workers should be aware of the early indicators of possible malignancies. The classic warning signs of cancer are listed below.
WARNING SIGNS OF CANCER
- Unusual bleeding or discharge anywhere in the body.
- Change in bowel or bladder habits (e.g., prolonged diarrhea or discomfort).
- A change in a wart or mole (i.e., color, size, or shape).
- A sore that does not heal (on the skin or in the mouth, anywhere).
- Unexplained weight loss.
- Anemia or low hemoglobin, and persistent fatigue.
- Persistent cough or hoarseness without reason.
- A solid lump, often painless, in the breast or testes or anywhere on the body.
Even if cancer is not present, any of these signs could be the indicator of some other disease process, so it should be checked by a physician. A critical observation can save a life. Sometimes a client may need encouragement to check out a suspicious lesion or change.
Local Effects of Tumors
- Pain is not usually an early symptom of cancer; rather, it occurs when the tumor is well advanced. Pain is a warning of a problem and therefore is helpful if it occurs early, but this is rare. The severity of the pain depends on the type of tumor and its location. Pain may be caused by direct pressure of the mass on sensory nerves, particularly where space is restricted (e.g., bone cancer). Dull, aching pain results from stretching of a visceral capsule such as occurs in the kidney or liver. Inflammation also contributes to pain because of increased pressure on the nerves and the irritation of nerve endings by chemical mediators. Secondary causes of pain include infection, ischemia, and bleeding. Blood can be "irritating" to tissues and, if it collects in an area, can cause pressure on nerves
- Obstruction can result when a tumor compresses a duct or passageway from an external position or grows inside a passageway or around a structure. Obstruction may occur in ducts or tubes in the body such as those in the digestive tract. Blood supply or lymphatic flow may be restricted, leading to ulceration and edema. Airflow in the bronchi or nerve conduction may be blocked. Obstructions can cause serious complications for the patient, even in the early stage. In the late stage, the prevention of obstruction may form the rationale for continuing palliative treatment.
- Tissue necrosis and ulceration may lead to infection around the tumor, particularly in areas where normal flora can become opportunistic. For example, infection is likely to be associated with cancer in the oral cavity. Host resistance to microbial invasion is often reduced with cancer.
Systemic Effects of Malignant Tumors
Systemic or general effects of cancer include the following:
- Weight loss and cachexia (severe tissue wasting) occur with many malignancies. Contributing factors include anorexia, fatigue, pain, stress, and the increased demands placed on the body by reproducing tumor cells (nutrient-trapping), altered carbohydrate and protein metabolism, and cachectic factors produced by macrophages in response to the tumor. This debilitation, in turn, leads to added fatigue and weakness and tissue breakdown;
- Anemia or decreased hemoglobin is a common problem resulting from anorexia and decreased food intake, chronic bleeding with iron loss, and bone marrow depression. Anemia decreases the oxygen available to cells, leading to fatigue and poor tissue regeneration;
- Infections such as pneumonia occur frequently as host resistance declines. Tissue breakdown develops and the immune system is less effective. The host's immobility contributes to infection in the lungs because of stasis of secretions in the lungs and weaker cough effort;
- Bleeding may occur because the tumor cells may erode the blood vessels or cause tissue ulceration. Bone marrow depression and hypoproteinemia may contribute to poor clotting. Chronic bleeding is common in the digestive tract, where the mucosa fails to regenerate quickly. Chronic blood loss leads to iron deficiency anemia; and
- Paraneoplastic syndromes are additional problems associated with certain tumors, such as bronchogenic carcinoma in the lungs. Tumor cells release substances that affect the neurologic function or blood clotting or have hormonal effects. For example, the cell of a bronchogenic carcinoma may produce adrenocorticotropic hormone (ACTH), leading to the manifestations of Cushing syndrome in the patient. This syndrome may confuse the diagnosis, complicate the monitoring of the patient, and create additional problems for the individual.
Diagnostic Tests
Tests are important in the early detection of cancer and in long-term monitoring of the patient subsequent to the diagnosis. Routine screening tests and self-examination programs need to be promoted, especially in high-risk clients. Frequent monitoring during and following treatment, as well as the ongoing follow-up, are important in assessing the effectiveness of treatment and providing a warning of recurrence. A diagnostic test is not usually 100% reliable by itself because there may be false-negative or false-positive results. The only definitive test for malignancy requires examination of the tumor cells. Other results should be assessed in conjunction with associated data. The following are selected types of tests used for the diagnosis of cancer:
- Blood tests are important both as an indicator of a problem and in monitoring the effects of chemotherapy and radiation. Hemoglobin and erythrocyte counts may below, a general sign of cancer. In some types of cancer, such as leukemia, the cell characteristics are diagnostic when confirmed by a bone marrow examination. Therapy frequently results in thrombocytopenia, erythrocytopenia, and leukopenia, and these may limit treatment at some point.
- Tumor markers are substances, enzymes, antigens, or hormones, produced by some malignant cells and circulating in the blood or other body fluid. These tumor cell markers can be used to screen high-risk individuals, to confirm a diagnosis, or to monitor the clinical course of a malignancy. Examples include Carcinoembryonic Antigen (CEA) for colon cancer, human chorionic gonadotropin (hCG) for testicular cancer, alpha-fetoprotein for hepatocellular cancer, CA125 for ovarian cancer, and prostate-specific antigen (PSA) for prostate cancer. Many of these substances are present with other diseases, and therefore their presence is not diagnostic by itself. Chromosome markers, such as the Philadelphia chromosome for chronic myelocytic leukemia, are also useful.
- X-ray, ultrasound, magnetic resonance imaging (MRI), and computed tomography (CT scans) are methods of examining changes in tissues or organs. In some cases, radioisotopes may be incorporated to trace metabolic pathways and function.
- Cytologic tests can be used to screen high-risk individuals, to confirm a diagnosis, or to follow a clinical course and monitor change. Histologic and cytologic examinations are used to evaluate biopsies of suspicious masses and to check sloughed cells in specific tissues (exfoliative cytology).
This is the only dependable confirmation of malignancy. An accurate evaluation depends on good technique and preservation of the specimen. For example, a regular Pap test examining cervical cells is a screening tool for cell changes indicating the development of cervical cancer. Increased use of this test has led to early detection and a greatly improved prognosis for cervical cancer patients.
The Spread of Malignant Tumors
Tumors spread by one or more methods depending on the characteristics of the specific tumor cells. They produce secondary tumors that consist of cells identical to the primary (parent) tumor.
Many cancers have already spread prior to diagnosis, and it is important to identify this activity before treatment begins. There are three basic mechanisms for the spread of cancer:
· Invasion refers to local spread, where the tumor cells grow into adjacent tissue and destroy normal cells. Tumor cells are loosely attached to other cells and also secrete lytic enzymes that break down tissue. The origin of the word cancer is the Latin word meaning "crablike," a good image of an invasive tumor;
· Metastasis means spread to distant sites by blood or lymphatic channels. In this case, the tumor cells erode into a vein or lymphatic, travel through the body, and eventually lodge in a hospitable environment to reproduce and create one or more secondary tumors. Only a few tumor cells survive this transfer, but it only takes a few to start a new tumor. Frequently, the first metastasis appears in the regional lymph nodes, which localize the tumor cells for a time. These lymph nodes are checked at the time of surgery, and often several are removed. Usually, the lymph nodes are removed or treated to eradicate any micro metastases that may be missed, particularly in cancers that are known to spread at an early stage (e.g., breast cancer). Many cancers spread by normal venous and lymphatic flow, and therefore the lungs and liver are common secondary sites for many tumors. Note a large number of secondary tumors in the liver shown in this figure. However, some cancers are more selective and spread to unusual sites; and
· Seeding refers to the spread of cancer cells in body fluids or along membranes, usually in body cavities. Again, the tumor cells break away and travel easily with the movement of fluid and tissue. An example is ovarian cancer, where the large peritoneal membrane encourages the dispersion of the tumor cells throughout the peritoneal cavity. Malignant cells may also be dislodged from the tumor if excessive handling occurs during diagnostic procedures or surgery, leading to further spread.
Staging of Cancer
Staging of cancer is a classification process applied to a specific malignant tumor at the time of diagnosis. It may be repeated at critical points. The staging system describes the extent of the disease at the time and therefore provides a basis for treatment and prognosis.
Staging systems are based on the:
• size of the primary tumor (T);
• extent of involvement of regional lymph nodes (N); and
• spread (invasion or metastasis) of the tumor(M).
Subgroups for each stage have also been established for many types of cancer. Generally, stage I tumors are small and well localized, easy to treat, and have a good prognosis, whereas stage IV tumors are well advanced, difficult to treat at multiple sites, and have a poorer prognosis.
