The second most available detection procedure is palpation. It is particularly valuable in detecting lumps, nodules, or tumors in the breast, mouth, salivary glands, thyroid, subcutaneous tissues, anus, rectum, prostate, testes, ovaries, and uterus and enlarged lymph nodes in the neck, axilla, or groin. Internal cancers require an extension of observation through endoscopes, x-rays, magnetic resonance imaging, and ultrasound. Laboratory tests, such as the Pap test, and occult blood testing of the feces have also proven helpful for some of these cancers. Concerns regarding effectiveness and yield, however, play a particularly important role in decisions to screen for cancers not easily amenable to earlier detection through physical examination in asymptomatic individuals.
Sensitivity is the chance that a person with cancer has a positive test.
Specificity is the chance a person without cancer has a negative test. PPV is the chance that a person with a positive test has cancer. NPV is the chance that a person with a negative test does not have cancer. PPV and, to a lesser degree, NPV are affected by the prevalence of disease in the screened population. Physician judgment is needed in such circumstances to determine the most appropriate application of available screening methods.