Definition – Hyperplasia is increase in number of cells in an organ or tissue resulting in increased volume of organ or tissue
Hyperplasia takes place if the cells are capable of synthesizing DNA, so that mitotic division can occur
Mechanism of hyperplasia
Hyperplasia is caused due to
Increased local production of growth factors
Increased levels of growth factor receptors on cells
Activation of intracellular signaling pathway
All these changes lead to production of transcription factors that turn on many cellular genes resulting in cellular proliferation. In hormonal hyperplasia, hormones by themselves act as growth factors
Hyperplasia can be physiologic or pathologic
Physiologic hyperplasia
Physiologic hyperplasia occurs when there is need for increased functional capacity of organs or as compensatory increase after damage or resection.
Examples of physiologic hyperplasia are
Hyperplasia of glandular epithelial cells of female breast at puberty, pregnancy and lactation
Compensatory hyperplasia of liver after partial hepatectomy
Bone marrow hyperplasia in response to deficiency of terminally differentiated blood cells as in case of acute bleed or hemolysis
Pathologic hyperplasia
Pathologic hyperplasia is caused due to excessive or inappropriate actions of hormones or growth factors
Examples of pathologic hyperplasia are
Hormonal hyperplasia:
Endometrial hyperplasia due to increase in estrogen
Benign prostatic hyperplasia due to androgens
Viral infections – As response to viral infections such as papilloma viruses, which cause skin warts and lesions composed of masses of hyperplastic epithelium
Pathologic hyperplasia have clinical significance because they constitute fertile soil for cancerous proliferation of the cells. Example: Endometrial hyperplasia can lead to endometrial adenocarcinoma
Hyperplasia differs from neoplasia in that hyperplasia persists until the stimulus for proliferation is present where as in neoplasia cell proliferation is not dependent upon growth regulatory mechanism.
Morphology
Gross: Size of the affected organ will be increased
Microscopy: Number of cells in organs will be increased with increase in mitotic activity
Reference
Vinay kumar, Abul k. Abbas, Jon C.Aster. Robbins and Cotran Pathologic Basis of Disease.2017; 9th edition.vol1.
Harsh Mohan. Text book of Pathology.2019.8th edition.