The exact stimulus for the development of an apocrine hidrocystoma is unknown. Plausible causes of the closely related eccrine hidrocystoma include occlusion or blockage of the sweat duct apparatus, which results in the retention of sweat and a dilated cystic structure.
Race: No known predilection exists for race or geographic region.
Sex: No known gender predilection exists.
Age: Cysts occur in adulthood, although in no particular age group.
History: Apocrine hidrocystomas usually are asymptomatic. No seasonal variation or familial tendencies have been identified. Cysts tend to appear during adulthood, grow slowly, and persist indefinitely.
The clinical appearance of a pea-sized cyst near the inner canthus of the eye, which contains a thin clear or pigmented fluid, suggests an apocrine hidrocystoma; however, histologic examination often is required to establish a specific and definitive diagnosis.
On histologic exam, apocrine hidrocystomas show large unilocular or multilocular cystic spaces within the dermis. Apocrine hidrocystomas are more likely to be multilocular than the closely related eccrine hidrocystoma.
A high power view of the linings of two of the cysts. A few brown, lipofuchsin pigment granules (PG) are in the basilar part of the epithelium. There is a suggestion of pigmented material in the apices of other cells. Apocrine snouts are prominent.
Well-organized fibrous tissue surrounds the cyst. Papillary projections extend from the secretory layer into the cyst cavity, depicting decapitation secretion.
The secretory cells are acid-Schiff–positive, and occasionally contain pigment granules, which provide the brown color of the cystic fluid. This pigment is neither melanin nor hemosiderin.
On electron microscopy, secretory cells have numerous, dense, lysosomal-type secretory granules typical of apocrine gland cells. They also have an increased number of annulate lamellae, which are unusual in normal apocrine cells.
If the diagnosis is made clinically without biopsy, a cystic basal cell carcinoma of the eyelid may be missed. Incision to observe the egress of fluid or biopsy of suspicious lesions excludes the possibility.
Pigmented BCC : In addition to features seen in lesions of nodular BCC, lesions of pigmented BCC contain increased brown or black pigment and are seen more commonly in individuals with dark skin.
Cystic BCC : Lesions of cystic BCC are translucent blue-gray cystic nodules that may mimic benign cystic lesions.
Superficial BCC : This variety presents as scaly patches or papules that are pink to red-brown in color, often with central clearing. Micronodular BCC: This aggressive BCC subtype has the typical BCC distribution. It is less prone to ulceration, may appear yellow-white when stretched, and is firm to touch.
Morpheaform and infiltrating BCC : These are aggressive BCC subtypes with sclerotic (scarlike) plaques or papules. The border usually is not well defined and often extends well beyond clinical margins.