Morphology

    Cancer tissue has a distinctive appearance under the microscope. These tissues appear as a large number of dividing cells and these cells present variations in nuclear size and shape, in cell size and shape, loss of specialized cell features, loss of normal tissue organization, and a poorly defined tumor boundary.

 Biopsy and microscopical examination can also distinguish between malignant cell and hyperplasic cells which lead to hyperplasia, which refers to tissue growth based on an excessive rate of cell division, leading to a larger than usual number of cells but with a normal orderly arrangement of cells within the tissue. This process is considered reversible. Hyperplasia can be a normal tissue response to an irritating stimulus, for example callus.

 Dysplasia is an abnormal type of excessive cell proliferation characterized by loss of normal tissue arrangement and normal cell structure. Often such cells come back to normal behavior, but occasionally, they gradually become malignant.

 The most severe cases of dysplasia are called "carcinoma in situ." In Latin, the term "in situ" means "in place", so carcinoma in situ refers to an uncontrolled growth of cells that remains in the original location and shows no intention to invade other tissues. Nevertheless, carcinoma in situ may develop into an invasive cancer. It is usually removed surgically, if possible.