Hidrocystomas are benign cyst tumors that are derived from sweat glands. They commonly affect the eyelid, are usually asymptomatic, affect both males and females, and are most common in adults. There are two types of sweat glands, the eccrine and the apocrine. Apocrine hidrocystomas aren't affected by temperature, but the eccrine hidrocystomas tend to grow larger when exposed to heat. The exact cause is unknown but it is thought that the eccrine hidrocystoma occurs due to the obstruction of the sweat gland which causes the retention of secretions and the appearance of a dilated cystic structure. The apocrine hidrocystoma is thought to be a benign tumor in the structure of the apocrine sweat gland. These are found only on certain areas of the body, such as the eyelids, armpits, areolae, external ear and genital region. Hidrocystomas are also commonly known as cystadenomas, sudoriferous cysts, and Moll's gland cysts.