1. Hyperplasia
- Definition: An increase in the number or density of normal cells in a tissue or organ, often in response to a stimulus or increased functional demand.
- Example: Benign Prostatic Hyperplasia (BPH)
- Description: This condition involves an increased number of normal cells within the prostate gland, leading to its enlargement. It is a common cause of urinary symptoms such as difficulty starting urination, weak urine flow, or frequent urination.
2. Metaplasia
- Definition: A reversible change where one differentiated adult cell type is replaced by another adult cell type, usually as an adaptive response to chronic irritation or stress.
- Example: Barrett’s Esophagus
- Description: In Barrett’s Esophagus, the normal squamous epithelial cells of the esophagus are replaced by columnar epithelial cells (found in the stomach or intestine) due to chronic irritation, often from gastroesophageal reflux disease (GERD). This adaptation increases the risk of developing esophageal cancer.
3. Dysplasia
- Definition: Abnormal and disorganized cell growth in a tissue, characterized by variations in cell size, shape, and appearance. It is potentially reversible but can progress to cancer if left untreated.
- Example: Cervical Dysplasia
- Description: This condition occurs when cells in the cervix exhibit abnormal growth and differentiation, often caused by infection with high-risk strains of human papillomavirus (HPV). Dysplasia can range from mild to severe and, if untreated, may progress to cervical cancer.
4. Anaplasia
- Definition: A regression of cells to an immature or undifferentiated state, often seen in malignancies. These cells lose their normal structure and function and grow uncontrollably. Anaplasia is not reversible.
- Example: Small Cell Lung Cancer (SCLC)
- Description: In this aggressive type of lung cancer, malignant cells show significant loss of differentiation and maturity. These undifferentiated cells divide rapidly, making the disease highly invasive and difficult to treat.