Apocrine hidrocystoma with mucinous metaplasia.

Hidrocystoma is a rare cystic lesion arising from the sweat glands, and is classified into apocrine and eccrine variants, with the majority being of apocrine nature [1]. It is usually found in the head and neck region, and commonly affects the periorbital area [1, 2]. Apocrine hidrocystoma is characterized histopathologically by the presence of a unilocular or multilocular cyst situated in the dermis, and the cyst wall is covered by a double layer of epithelial cells [1, 2]. The inner layer is composed of columnar cells with rich eosinophilic cytoplasm which shows luminal decapitation secretion, and the outer layer is consisted of flat myoepithelial cells [1, 2]. Occasionally, papillary projection of the epithelium into the lumen is observed, which is referred to as papillary apocrine gland cyst [1].