Chapter at a Glance

Use this list of word parts and key terms to assess your knowledge. Check off the ones you have mastered.

Specialties/Specialists

Oncology is the study of tumors, both benign (noncancerous) and malignant (cancerous). An oncologist is a specialist in the diagnosis, treatment, and prevention of tumors.

Cancer registrars (also called tumor registrars) are specialists in cancer data management. Their primary responsibility is to report and track patients with cancer who are diagnosed and/or treated at the registrar’s healthcare facility.

Carcinogenesis

Cancer is not one disease but a group of hundreds of diseases with similar characteristics. The shared characteristics are uncontrolled cell growth and a spread of altered cells. Different types of cancers have different occurrence rates and different causes.

Current research suggests that there is no single cause of cancer. Radiation, bacteria, viruses, genetics, diet, smoking (or exposure to tobacco smoke), alcohol, and other factors all contribute to the development of cancer termed carcinogenesis. Each of these factors is instrumental in disrupting the normal balance of cell growth and destruction within the body by causing a mutation in the DNA of cells (Fig. 16-1). Once this mutation takes place, a process of uncontrolled cell growth may begin. It is important to note that the cancer cells that replace normal cells no longer function to keep the body working. The only mission of cancer cells is to reproduce. Fig. 16-2 illustrates the process of apoptosis (a pop TOH sis), the body’s normal restraining function to keep cell growth in check. Fig. 16-3 shows the progression from normally functioning skin tissue to hyperplasia, to dysplasia, and finally to carcinoma in situ (CIS). Cancer is a continuum—from tissue made up of normally functioning cells fulfilling their role to keep the body healthy, to tissue replaced by cancerous cells that no longer perform the work of the tissue and now perform only the function of reproducing themselves. Cancers are capable of destroying not only the tissue in which they originate (the primary site), but also other tissues, through the process of metastasis, the spread of cancer. Metastasis can occur by direct extension to contiguous organs and tissues or to distant sites through blood (Fig. 16-4) or lymphatic involvement.

Naming Malignant Tumors

All cancers are neoplasms (new growths), but not all neoplasms are cancerous. Cancerous tumors are termed malignant, whereas noncancerous tumors are termed benign.

Although the hundreds of known types of malignant tumors commonly share the characteristics listed previously, the names that they are given reflect their differences. All tissues (and hence organs) are derived from the progression of three embryonic germ layers that differentiate into specific tissues and organs. Tumors are generally divided into two broad categories and a varying number of other categories, based on their embryonic origin. Fig. 16-5 illustrates the different types of cancers and where they occur.

Staging and Grading

To treat cancer, the treating physician must determine the severity of the cancer, the grade, and its stage, or size and spread. Cancers at different grades and stages react differently to various treatments.

Grading is the first means of affixing a value to a clinical opinion of the degree of dedifferentiation (anaplasia) of cancer cells, or how much the cells appear different from their original form. Healthy cells are well differentiated; cancer cells are poorly differentiated. The pathologist determines this difference and assigns a grade ranging from I to IV. The higher the grade, the more cancerous, or dedifferentiated, is the tissue sample. Grading is a measure of the cancer’s severity.

The other means of determining the size and spread of the cancer from its original site, which is called staging. A number of systems are used to describe staging. Some are specific to the type of cancer; others are general systems. If staging is determined by various diagnostic techniques, it is referred to as clinical staging. If it is determined by the pathologist’s report, it is called pathologic staging. An example is TNM staging. In this system, T stands for the size of the tumor, N stands for the number of lymph nodes positive for cancer, and M stands for the presence of distant metastasis (meh TAS tuh sis). Summary staging puts together the TNM to give one number as a stage. Again, this helps the clinician to determine the type of treatment that is most effective. Fig. 16-6 illustrates a staging system. If the cancer cells appear only at the original site and have not invaded the organ of origin, it is called carcinoma in situ (CIS).

Cancer that begins in an organ is referred to as a primary tumor. When a cancer spreads to another site in the body from that primary tumor, the new tumor is referred to as secondary, or metastatic. The cells in the metastatic tumor are composed of the same tissue as the cancer at the original site. For example, a patient can have a primary liver cancer that begins in the liver, or a metastatic brain tumor that is composed of cells from a primary liver cancer that has spread.

 Exercise 1 General Oncology Terms

Match the word part with its correct meaning.

Underline the correct answer.

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