Ocular Pathology

Anatomy and pathology of the human eye. Use it to review eye pathology for Ophthalmology Board Review or OKAP.

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Friday, January 26, 2007

Apocrine & Eccrine Hidrocystomas, Ductal Cyst

Definition: benign cystic lesions of the eyelid characterized by cuboidal epithelium and fluid content. Apocrine hidrocystomas are characterized by apical budding, eccrine hidrocystomas by a cuboidal lining without apical buds and cystic contents with clear fluid and the term ductal cyst as a deliberately vague term which in some reports captures all classifcations. Presumably such a cyst would recapitulate the ducts which in fact lack the features seen in the cysts. However these terms are bantered about in the literature and there appears to be some overlap morphologically and understandable confusion.
Incidence/ Prevalence: Although not thoroughly studied hidrocystomas account for less than 5% of all eyelid biopsies.
Etiology: Some have aveered that most of the hidrocystomas arise from apical epithelium, based mainly on their anatomic location and histologic appearance and immunohistochemical evidence albeit weak.
Clinical Findings: The mean age is about 59 years with a range from 39-91 in one series (Singh et al). The patient usually present with a single clear cystic tumor that is close to but not involving the upper eyelid margin. The lesions are usually solitary (71%), and located on the upper eyelid (2/3). Almost all are less than a cm in size and 1/3 are less than 1 mm. About 90% are close to the eyelid margin but generally don’t involve the margin. Proximity to the lid margin has been propounded as evidence for an apocrine origin since the normal glands are close to the canthi and eyelid margins whereas eccrine ducts were not found in these regions. Less than 10% are pigmented. The lesions may be bilateral although this is also rare.
Gross: The lesion is cystic, contains clear fluid and lined by a smooth surface with occasional infoldings. In the accompanying image one can see a clear cyst (magnified of course) demarcated by the black arrows. There is surrounding fibrous tissue as this lesion was shelled out from the conjunctival surface. Hidrocystomas may arise from the conjunctiva as well as from eyelid. Cysts often contain clear fluid as opposed to keratinaceous material that is often seen in epidermal or sebaceous types of cysts.

Histopathology: The classic description features a cystic cavity (number 1) with lightly eosinophilic staining material in the center. There is perhaps eosinophilic proteinaceous contents here although it is poorly defined (arrows 5). Eccrine hidrocystoma is lined by a double layer of cuboidal cells (arrows 2 and 3). The inner layer facing the cyst shows some minor budding toward the lumen arrow 2).

However, often the basal layer is actually flattened evidence that this cyst is of ductal origin. Note in the figure that the surface of the biopsy specimen is keratinized stratified squamous epithelium. This finding may seem trivial but indicates that the location is skin at least slightly away from the eyelid margin; sometimes pathologists are not given that information. Also note just for fun, the pigmentation of the basal layer, extravasated erythrocytes and free pigment in the superficial dermis in combination with a mild perivascular inflammatory infiltrate. Not all hidrocystomas have a uniform or consistent lining we have seen parts of the cyst lined by stratified squamous epithelium. Some have only focal apical buds and the immunohistochemical evidence presented by Jakobiec was not specific as GCDFP-15, CD17 and SMA may be positive in various areas of normal glands of both eccrine and apocrine origin although not their ducts. By his criteria eccrine hidrocystomas are vanishingly rare in the eyelid and the term ductal cyst is used in his work form both eccrine and apocrine cysts further beclouding the topic. Perhaps it is rational to refer to these cysts as hidrocystomas or ductal cysts until specific scientific evidence is presented to separate these entities.
Treatment: Complete excision is generally performed without recurrence.
1. Singh et al. Eye 2005 19;77-9.
2. Jakobeic et al. AJO 2011:151:358

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