Dermatofibroma are common benign skin tumours that cause lumps in the skin and frequently cause concern upon discovery. The causes of dermatofibroma may include a reaction to trauma such as insect bites but the precise cause is often unclear.
Causes. It's not clear what causes simple kidney cysts. One theory suggests that kidney cysts develop when the surface layer of the kidney weakens and forms a pouch (diverticulum). The pouch then fills with fluid, detaches and develops into a cyst. 1  Symptoms. 2  Risk factors.
Simple kidney cysts are abnormal, fluid-filled sacs that form in the kidneys. Simple kidney cysts are different from the cysts that develop when a person has polycystic kidney disease (PKD), which is a genetic disorder. Simple kidney cysts do not enlarge the kidneys, replace their normal structure, or cause reduced kidney function like cysts do in people with PKD. Simple kidney cysts are more common as people age. An estimated 25 percent of people 40 years of age and 50 percent of people 50 years of age have simple kidney cysts. 1. Simple kidney cysts are abnormal, fluid-filled sacs that form in the kidneys. What are the kidneys and what do they do?