Apocrine Hidrocystoma

Etiology

Apocrine hidrocystomas arise from an inappropriate tumorous growth of apocrine sweat glands [1]. The exact etiology of causes of theses growths is unknown and it not known to be associated with a familial incidence.

Epidemiology

Apocrine hidrocystoma is mainly observed in adults aged 30 to 70 years and rarely occurs during childhood or adolescence [2]. Solitary apocrine hidrocystoma is equally noticed in males and females, and there is no ethnic predominance or geographic region predilection. Multiple forms of apocrine hidrocystoma are rare in the general population. 

Pathophysiology

The pathogenesis of apocrine hidrocystoma is not entirely known. The tumor derives from the secretory part of apocrine sweat glands. Apocrine hidrocystoma is currently considered to be a cystic proliferation of apocrine glands, rather than a simple retention cyst. Multiple apocrine hidrocystomas have been described in two rare ectodermal dysplasias: a particular form of Goltz-Gorlin syndrome and Schopf-Schultz-Passarge syndrome. Goltz-Gorlin syndrome (Focal dermal hypoplasia) is an X-linked dominant disease characterized by linear skin atrophy, microcephaly, microphthalmia, midfacial hypoplasia, malformation of the ears, mental retardation, and skeletal abnormalities. Some additional clinical findings were described in a particular form combining multiple apocrine hidrocystomas, bilateral keratoconus, esophageal papillomatosis and hiatus hernia. Schopf-Schultz-Passarge syndrome is an autosomal recessive condition characterized by the association of multiple eyelid apocrine hidrocystomas with hypotrichosis, hypodontia, palmar and plantar hyperkeratosis, as well as nail fragility [3][4][5].

Histopathology

The inner cyst wall of the apocrine hidrocystoma is lined by a luminal layer of columnar cells indicating apocrine secretion and a peripheral layer of flattened myoepithelial cells, similarly seen in the secretory portion of the normal apocrine gland [5]. Apocrine hidrocystoma can present as unilocular or multilocular [5]. The epithelium can be either a single or double layer of cuboidal-columnar epithelium, located superiorly to an outer myoepithelial cell layer [5]. PAS-positive granules are also seen with lipofuscin granules. Apocrine hidrocystomas also exhibit papillary projections which are vascular connective tissue, covered by the secretory epithelium [5].

History and Physical

Apocrine hidrocystoma is most often a solitary tumor, although practitioners have also documented multiple lesions. Apocrine hidrocystoma is typically intradermal, moderately firm, dome-shaped, translucent, blue, bluish-black, grayish, or purple cystic nodule. Its size ranges from 3 mm to 15 mm in diameter [6]. Giant variants measuring up to 7 cm in diameter can rarely occur. Apocrine hidrocystoma is more frequently pigmented than eccrine hidrocystoma. Apocrine hidrocystoma does not change or become symptomatic in hot weather [5].

Apocrine hidrocystoma is usually found on the head, face and neck. This is probably because apocrine glands are frequent in these locations [7].

The main differential diagnosis of the rare cases of multiples apocrine hidrocystomas is multiple eccrine hidrocystomas. Eccrine hidrocystomas are smaller, with a diameter ranging from 1 mm to 6 mm [6]. Their color is brown or bluish, clearer than that of apocrine hidrocystomas. Another important differential fact is that eccrine hidrocystomas increase in size and number in summer months or heated environment and may disappear entirely in cooler weather [6]. 

Evaluation

Dermoscopic findings show a homogeneous pale gray or bluish pattern, whitish cotton wool-like structures, linear vessels, and nonconstant focal brownish orange areas. The grayish color is probably due to the presence of sialomucin which induces an effect of diffraction as seen in Kaposi sarcoma. The whitish structures are due to a reflection of the connective tissue, and the brownish orange structures could be explicated by the presence of clear cells containing important amounts of glycogen. The dermoscopic sign of the peripheral linear vessels corresponds to the dilated vessels of the papillary dermis. The main interest in dermoscopy is to make sure the absence of dermoscopic features of a malignant tumor that may have a similar clinical presentation (mainly amelanotic melanoma and basal cell carcinoma).[8][9][10][11]

While apocrine hidrocystomas can be suspected clinically, they can only be diagnosed histologically, with a tissue sample examined under a microscope.

Treatment / Management

The most common treatment of apocrine hidrocystoma is surgical excision with narrow margins, because of the benign nature of the lesion. This is the only approach that allows a practitioner to carry out both the final diagnosis and the treatment of these tumors. An alternative therapy is needle puncture; however, local recurrence is frequently observed with this treatmen [6]. Cyst puncture followed by hypertonic glucose sclerotherapy was used successfully in the treatment of eyelid apocrine hidrocystoma [12]. Trichloroacetic acid injection (followed by aspiration) after cyst puncture may also be an alternative to surgery [13]. Botulinum toxin A has been used effectively, as well [13].(B3)

Differential Diagnosis

• Basal cell carcinoma

• Blue nevi

• Cutaneous melanoma

• Eccrine cystadenoma

• Follicular cyst

• Milia

• Syringoma

Prognosis

The prognosis is fair, as apocrine hidrocystomas are benign tumorous growths that pose no risk of metastasis. 

Complications

There are no known complications of untreated apocrine hidrocystomas.