Apocrine Hidrocystoma

Apocrine hidrocystomas are benign cystic proliferations of the apocrine secretory glands. Apocrine hidrocystomas most commonly appear as solitary, soft, dome-shaped, translucent papules or nodules and most frequently are located on the eyelids, especially the inner canthus. Apocrine hidrocystomas grow slowly and usually persist indefinitely.

Although the origin of apocrine hidrocystomas is not known entirely, they are believed to be adenomatous cystic proliferations of the apocrine glands. 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.

US frequency

Apocrine hidrocystomas are relatively common in the United States.

Race

No predilection for race or geographic region is recognized for apocrine hidrocystomas.

Sex

No sex predilection is described for apocrine hidrocystomas.

Age

Apocrine hidrocystomas occur in adulthood, although in no particular age group.

Apocrine hidrocystomas grow gradually and persist indefinitely after attaining full size. They seldom recur after removal. Apocrine hidrocystomas are entirely benign. Cysts may annoy patients; however, symptoms usually are mild or absent. Vision usually is not affected.

Advise patients that apocrine hidrocystomas are benign.

Apocrine hidrocystomas usually are asymptomatic. No seasonal variation or familial tendencies have been identified. Apocrine hidrocystomas tend to appear during adulthood, grow slowly, and persist indefinitely.[1]

Apocrine hidrocystomas usually occur as solitary translucent papules or nodules. Consistency is fluctuant and cystic. Size varies from a few millimeters to approximately 1.5 cm. Tumors occasionally manifest as multiple lesions, especially when of the eccrine hidrocystoma type.[2, 3, 4, 5, 6]

Apocrine hidrocystomas often appear tense and shiny. The coloration varies from flesh-colored to blue or black (see image below).

Tumors have a predilection for the eyelid, particularly the inner canthus. Tumors may arise on other areas of the head, neck, and trunk.[7] Tumors also have been reported to occur on the penis, in the axillae, and in the anal region. Rare reports describe an apocrine hidrocystoma on the parotid gland[8] and an epibulbar subconjunctival apocrine hidrocystoma.[9]

Lesion edges are not well delineated but blend gradually into adjacent skin. Walls, although translucent, are sufficiently thick that they seldom rupture spontaneously.

When incised, apocrine hidrocystomas collapse, and a thin, clear, brownish, or blackish fluid is released. The fluid color of an apocrine hidrocystoma does not result from the presence of melanin or hemosiderin but may result either from the Tyndall phenomenon or the presence of lipofuscin pigment.

Cysts are mobile with palpation and transilluminate.

Apocrine hidrocystomas are not affected by variation in temperature (unlike eccrine hidrocystomas).

Diagnosis is made easily by biopsy.

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. Upon histologic examination, apocrine hidrocystomas show large unilocular or multilocular cystic spaces within the dermis (see the image below). Apocrine hidrocystomas are more likely to be multilocular than the closely related eccrine hidrocystoma.

The cyst wall is lined by apocrine-type secretory epithelium. The innermost layer of the wall is composed of a single (occasionally double) layer of cuboidal-to columnar-shaped cells. The nuclei of these cells are positioned basally. The outer layer of cells composing the cyst wall is formed by myoepithelial cells in which the long axes run parallel to the cyst wall.

Well-organized fibrous tissue surrounds the cyst. Papillary projections extend from the secretory layer into the cyst cavity, depicting decapitation secretion. The secretory cells contain periodic acid-Schiff–positive, diastase-resistant granules 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.

On dermoscopy, aprocrine hidrocystomas often have a homogenous area that occupies the whole lesion and that may be accompanied by arborizing vessels. The color of the homogenous area can be skin colored, yellow, or blue.[10]

Apocrine hidrocystomas can be incised and drained; however, electrosurgical destruction of the cyst wall often is recommended to prevent recurrence. Punch, scissors, or elliptical excision also can remove tumors. Multiple apocrine hidrocystomas can be treated with carbon dioxide laser vaporization.[11] Trichloroacetic acid has also been used.[12] One report suggests that multiple or recurrent hidrocystomas may be amendable to botulinum toxin A injection, with improvement.[13]