HIDROCYSTOMA
Hidrocystomas, also known as
eccrine hidrocystomas, are common benign skin tumors that are most frequently
found along the eyelid margin. These benign tumors have a typical appearance
and no malignant potential. Most often, they manifest as solitary, asymptomatic
papules.
Clinical Findings: Eccrine hidrocystomas manifest as solitary, translucent, pale, clear
to blue or light purple papules. They have a smooth surface and a dome shape.
Eccrine hidrocystomas are soft; they feel as if pressure could easily rupture
their cystic wall. Puncturing of the cyst wall with a 30-gauge needle causes
drainage of a thin, watery fluid. These tumors are almost always asymptomatic.
They can occur at any age but are far more common after the fourth decade of
life. No difference in incidence has been observed based on race or gender.
Lesions are typically small, 5 mm to 1 cm in diameter, and can fluctuate in
size. It is not uncommon for a patient to relate that the tumor enlarges during
physical exercise, only to shrink after a few days. If ruptured, these tumors
drain a thin, watery liquid, and the cystic cavity deflates. Although they are
almost always solitary, there are reports of hundreds of these tumors
developing in some patients. Large eccrine hidrocystomas occurring in atypical
locations have also been described.
The main differential diagnosis is between eccrine
hidrocystoma and basal cell carcinoma. Cystic basal cell carcinomas can have an
identical appearance; however, the patient history will be quite different.
Basal cell carcinomas typically enlarge over time and ulcerate, causing
bleeding of the ulcerated papule. Hidrocystomas rarely, if ever, ulcerate or
bleed. If left alone, they only transiently increase in size and never get much
larger than 1 cm in diameter, and usually they are much smaller. A biopsy for
pathological evaluation is diagnostic.
Pathogenesis: Hidrocystomas
develop from the eccrine apparatus. It is believed that a portion of the
eccrine duct within the dermis becomes occluded. This occlusion causes a
buildup of eccrine secretions proximal to the blockage. Once enough fluid
collects, a translucent papule becomes evident on the surface of the skin. No
genetic abnormalities of the involved eccrine duct have been discovered, and
this cystic formation is most likely caused by damage from superficial trauma
to the skin and the underlying eccrine ducts. Sun damage to the eccrine ducts
has been theorized to play a role, although this theory has yet to be vigorously
tested.
Histology: A lone
cystic space is seen within the dermis. The cyst is well circumscribed, and the
lining of the cyst contains two layers of cells. The cells are cuboidal and
have an eosinophilic cytoplasm. The cell wall has no myoepithelial cell
component. The cysts are found near eccrine gland structures. There is minimal
to no inflammatory infiltrate surrounding the cyst. The central cavity of the
cyst contains an small amount of lightly eosinophilic material that is consistent
with eccrine gland secretions. There is no evidence for sebaceous gland or
apocrine gland secretion or derivation.
Treatment: Most
eccrine hidrocystomas are biopsied to make sure they are not actually basal
cell carcinomas. They rarely recur after biopsy. If they do recur, no treatment
is required. Surgical excision is the definitive treatment and is cur tive.
Hidrocystomas almost never recur after excision.
