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.
For example, ovarian cysts, such as those that result from polycystic ovary syndrome (PCOS), can cause hormonal problems. Polycystic kidney disease (PKD), which causes cysts to form in the kidney, can affect kidney function. Cysts usually grow slowly and have a smooth surface.