To diagnose the presence of cancer, a doctor must look at a sample of the affected tissue under the microscope. Hence when preliminary symptoms, Pap test, mammogram, PSA test, or fecal occult blood test indicate the possible existence of cancer, a doctor must then perform a biopsy, which is the surgical removal of a small piece of tissue for microscopic examination. (For leukemias, a small blood sample serves the same purpose.) Microscopic examination will tell the doctor whether a tumor is actually present and if so, whether it is malignant (cancer) or benign.
Microscopic Appearance of Cancer Cells
Cancer tissue has a distinctive appearance under the microscope. Among the traits the doctor looks for are a large number of dividing cells, variation in nuclear size and shape, variation in cell size and shape, loss of specialized cell features, loss of normal tissue organization, and a poorly defined tumor boundary.
Instead of finding a benign or malignant tumor, microscopic examination of a biopsy specimen will sometimes detect a condition called "hyperplasia." Hyperplasia refers to tissue growth based on an excessive rate of cell division, leading to a larger than usual number of cells. Nonetheless, cell structure and the orderly arrangement of cells within the tissue remain normal, and the process of hyperplasia is potentially reversible. Hyperplasia can be a normal tissue response to an irritating stimulus. For example, a callus that may form on your hand when you first learn to swing a tennis racket or a golf club is produced by hyperplasia.
In addition to hyperplasia, microscopic examination of a biopsy specimen can detect another type of noncancerous condition called "dysplasia." Dysplasia is an abnormal type of excessive cell proliferation characterized by loss of normal tissue arrangement and cell structure. Often such cells revert back to normal behavior, but occasionally, they become malignant overtime. Because of their potential for becoming malignant, areas of dysplasia should be closely monitored by a health professional. Sometimes they need treatment.