Hidrocystoma is an adenoma

Adenoma

An adenoma is a benign tumor of glandular origin. Adenomas can grow from many organs including the colon, adrenal glands, pituitary gland, thyroid, prostate, etc. Although these growths are benign, over time they may progress to become malignant, at which point they are called adenocarcinomas...

 of the sweat gland

Sweat gland

Sweat glands, or sudoriferous glands, are small tubular structures of the skin that produce sweat. There are two kinds of sweat glands:...

s.

Hidrocystomas are cysts of sweat ducts, usually on the eyelids.
Histrocystomas are not tumours. (A similar sounding lesion called hidroadenoma is a benign tumour.)

There are three types of "sweat" glands: True sweat glands or eccrine glands,
sebaceous glands which have an oily secretion around hair follicles and apocrine glands which have more oily product than eccrine glands and are found on the face, armpit and groin.

Hidrocystomas usually arise from apocrine glands. They are also called Cysts of Moll or sudoriferous cysts. There may be a type of hidroadenoma that arises from eccrine glands but these are uncommon.

Other related conditions on the eyelids include chalazion ( a granulomatous reaction to sebaceous glands on the eyelid), lacrimal duct cysts (cysts related to tear ducts) and nasolacrimal duct cysts (the nasolacrimal duct drains tears into the nose via a punctum on the lower eyelid).

See also

• Syringoma
• Acrospiroma
  Acrospiroma
  An acrospiroma is a tumor of the distal portion of a sweat gland. Acrospiromas are usually benign, and treatment consists of surgical excision....
  
  
• Seborrheic keratosis
  Seborrheic keratosis
  A seborrheic keratosis is a noncancerous benign skin growth that originates in keratinocytes. Like liver spots, seborrheic keratoses are seen more often as people age. In fact they are sometimes humorously referred to as the "barnacles of old age". They appear in various colors, from light tan to...
  
  
• List of cutaneous conditions