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.
Complex cysts pose a concern because a subset of complex cysts may have cancerous growth. Of note, most cancerous growths in the kidney are solid, not cystic. Yet some cancers of the kidney may have a cystic component. Strategies are available to predict whether a complex cyst may be associated with cancerous change.