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Dermpath-India Pathology of Hidrocystoma-(Apocrine and Eccrine) Dr Sampurna Roy MD 2022
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The hidrocystomas are
cystic forms of sweat gland resulting from proliferation of the apocrine
secretory coil or eccrine duct.
Eccrine hidrocystomas are benign tumors of the sweat glands that arise from cystic dilatation of the excretory sweat duct. They typically present as multiple skin-colored to bluish cystic papules in the centrofacial area and are most commonly seen in middle-aged women. Aggravation in summer, in humid environments, during exercise and other conditions that involve intense sweating is characteristic for eccrine hidrocytomas . Apocrine hidrocystomas are adenomatous cystic proliferation of apocrine glands. Some regard them as retension cysts, others regard some of these lesions with epithelial proliferation as benign tumours (Apocrine Cystadenoma). Apocrine hidrocystoma (apocrine cystadenoma) was first described by Mehregan in 1964 and eccrine hidrocystomas, first described by Robinson in 1893.
Clinical presentation: Eccrine hidrocystoma is usually unilocular, whereas apocrine hidrocystomas are multilocular containing clear or brownish fluid. It is suggested that the pigmentation observed clinically is due to the Tyndall phenomenon. Site: Apocrine and eccrine hidrocystomas are prevalent in adults between 30 and 75 years of age, and the lesions are generally distributed in similar locations on the body. The commonest site for such lesions is around the eye, and they may also occur on the ears, scalp, chest, shoulders, or feet. Microscopic features: Under the microscope, eccrine hidrocystomas appear as unilocular cysts, which usually contain a single cystic cavity composed of 1 or 2 layers of cuboidal cells. They are located within the mid-dermal to superficial layers of the skin, especially around the eyes. Unlike their apocrine counterpart, there are no secretory cells seen and decapitation of cells is not viewed under the microscope. Histochemically, they stain positive for S100 protein (solitary type), whereas apocrine hidrocystomas do not. The cyst and epidermis do not communicate, and the periodic acid-Schiff (PAS)-positive granules are not observed. In apocrine hidrocystomas the cysts are lined by two layers of cells. The inner layer consists of tall columnar cells with eosinophilic cytoplasm and showing decapitation secretion. The outer layer consists of myoepithelial cells. The apocrine cells probably contain lipofuscin granules. These granules are PAS positive and diastase resistant. Rarely, the lining epithelium shows papillary proliferation
and are known as Papillary apocrine
gland cyst. (Differential Diagnosis :
Hidradenoma papilliferum or
syringocystadenoma papilliferum.) Hidrocystomas may be eccrine or apocrine, and a specific diagnosis is possible only after staining for human milk fat globules or gross cystic disease fluid protein 15 . Immunohistochemically,apocrine hidrocystomas are positive for human milk fat globules, gross cystic disease fluid protein 15 , CK7 and CK18 in the inner layer of epithelium, and also positive for α-smooth muscle actin in the outer myoepithelial cells, whereas eccrine hidrocystomas are negative for all of these.
Apocrine hidrocystomas grow gradually and usually do not recur after excision.
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