Hidrocystomas are benign cystic proliferations of the sweat glands with apocrine or eccrine differentiation. The tumour most commonly arises in the face and neck and presents as a well-circumscribed, dome-shaped, cystic, papular or nodular lesion measuring typically between 0.5 and 1 cm (rare cases up to 7 cm). The lesion is uni- or multilocular and lined by a double layer of epithelium. Large columnar cells characterized by an eosinophilic cytoplasm and luminal decapitation secretion make up the inner layer, while the outer layer consists of flat myoepithelial cells.
Hidrocystomas are relatively rare. They may arise in all age groups but are most common in middle-aged and elderly individuals. An increased incidence is observed in hyperthyroid patients. Complete surgical excision is usually curative. Tumours have been reported to completely disappear with cold weather and atropine therapy, whereas high temperatures appear to have an exacerbating effect
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