HYPERPLASIA

n. excessive cell reproduction (Medicine)

Hyperplasia (or "hypergenesis") is a general term referring to the proliferation of cells within an organ or tissue beyond that which is ordinarily seen. Hyperplasia may result in the gross enlargement of an organ, the formation of a benign tumor, or may be visible only under a microscope. Hyperplasia is considered to be a physiological response to a specific stimulus, and the cells of a hyperplastic growth remain subject to normal regulatory control mechanisms. This stands in contrast to neoplasia (the process underlying cancer and some benign tumors), in which genetically abnormal cells proliferate in a non-physiological manner which is unresponsive to normal stimuli.
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Hyperplasia /hy·per·pla·sia/ abnormal increase in the number of normal cells in normal arrangement in an organ or tissue, which increases its volume. [more]Hyperplasia - Community and Resources

Noun
1. abnormal increase in number of cells
(hypernym) dysplasia
(hyponym) benign prostatic hyperplasia, BPH

(n.)
An increase in, or excessive growth of, the normal elements of any part.