Definition: Megaplasia, a term in medicine, refers to an abnormal growth or thickening of tissue that can result from several factors including infection, trauma, or cancer. It's a condition where the affected area becomes so dense and swollen it looks like a mushroom cap. Megaplasia is primarily seen in the lungs, but also found in other organs such as the stomach, liver, brain, and even the heart if present. Understanding megaplasia helps in diagnosing conditions related to lung tissue changes due to various factors affecting breathing patterns or functions.