Tumor, Benign

Risk: It is unclear what causes the development of benign tumors. Many factors, including environmental toxins, genetic influences, diet, emotional stress, local trauma or injury, and inflammation are thought to be possible causes, either singly or in combination. In some cases, particularly if hormone receptors are present on the multiplying cells, gender may be a factor in the development of certain types of benign tumors (e.g., women are subject to the development of hormone-related uterine tumors called fibroids). Nevertheless, most benign tumors occur with equal frequency in both sexes and can develop in almost any region of the body.

Incidence and Prevalence: Since many benign tumors are asymptomatic, incidence is difficult to determine. Benign tumors represent about 2% to 5% of all tumors found in the lungs, and up to 50% can later become malignant (Gould).

History: Symptoms depend on the cell type of origin, size and location of the growth, and the organ system involved. Individuals may report noticing a lump or skin change. If an abdominal tumor is pressing on the stomach or nearby structures, individuals may complain of nausea, a sense of fullness, or weight loss. When tumors compress or disturb nerves, they can cause pain or disorders such as dizziness, unsteadiness, vision problems, weakness, or headaches.

Physical exam: Physical findings vary according to the site and size of the tumor. Examination may reveal a lump or skin change when the tumor is located in the soft tissue such as the breast, abdomen, muscle, or skin. However, if the tumor is small and is located in a deep structure such as the lungs, brain, or other organs, no physical abnormalities may be found.

Tests: Diagnostic imaging may be used to visualize internal organs and to determine the location and size of a suspected tumor. X-ray, ultrasound, high resolution computed tomography (CT), or magnetic resonance imaging (MRI) may be used either alone or in combination to examine tissue in more detail, depending on location involved. Direct inspection of certain internal organs may require the use of an endoscope, a small, lighted fiberoptic instrument that is passed into the organ or cavity being examined. This minimally invasive technique is used most often for examinations of abdominal or pelvic organs such as the colon (colonoscopy), stomach and adjacent organs of the gastrointestinal tract (gastroscopy), bladder (cystoscopy), and abdominal cavity (laparoscopy). Thoracotomy or thorascopy may be used to examine the lungs.

Differentiating between benign and malignant tumors requires an evaluation of tumor cells by a pathologist (histopathologic examination). Diagnosis usually is confirmed by microscopic examination of tumor tissue cells that have been removed surgically (biopsy) or aspirated by needle biopsy and stained by appropriate techniques. For example, up to 50% of benign lesions in the lung are identified by biopsy and cell differentiation study (Gould). Differentiation refers to the extent to which cells resemble the normal cells of origin in terms of size, morphology, and function. Differentiation can range from well-differentiated, as in benign lesions, to moderately well differentiated, which can be either benign or malignant, to cells showing much less differentiation (anaplastic), or undifferentiated; anaplastic and undifferentiated lesions are characteristically malignant with many changes in size, shape, and degree of proliferation. Benign tumor cells retain many of the same features as the cells of the tissue from which they arose, although the tumor tissue typically will be denser than normal tissue, and cell proliferation will be less than in malignant tumors.

Distinguishing between a benign and malignant lesion also depends on the presence of metaplasia or dysplasia in the tissue. Metaplasia describes a condition of tissue damage, repair, and regeneration of cells; however, the replacement cells are not of the same type as the original tissue. The cells in the tumor are abnormal and have differentiated into tissue of another kind. Dysplasia refers to disordered growth that includes loss of uniformity among cells and changes in their composition that are typical of malignant neoplasms.