The concept of differentiation of neoplasms is demonstrated by this small benign adenomatous polyp (tubular adenoma) of the colon. Note the difference in staining quality between the epithelial cells of the adenoma at the top and the normal glandular epithelium of the colonic mucosa below. The neoplastic glands do not look exactly like the normal glands, but they are recognizable as glands, and would still be termed well differentiated.
In regard to differentiation, neoplasms range from well-differentiated to moderately differentiated to poorly differentiated. In general, less differentiation means that the neoplasm is more likely malignant and more likely to be aggressive. However, differentiation is just one of many variables that point to the potential biologic behavior of neoplasms.