Histopathologic examination revealed cystic spaces in the dermis, with some papillary projections. There were an inner layer of cells with abundant cytoplasm and basally located nuclei, an outer layer of spindle-shaped cells, and areas of decapitation secretion.
Apocrine hidrocystoma, or apocrine cystadenoma, is a benign, adenomatous cystic proliferation derived from apocrine glands that is most commonly seen in middle-aged individuals.1,2 Its typical clinical appearance is of an asymptomatic, solitary cyst measuring between 0.3 and 1.5 cm in diameter, but there have been reports of lesions as large as 7 cm in diameter.3,4 The lesions, which are usually smooth surfaced and slightly more firm than the surrounding skin, may be skin colored to blue, brown, or black, with bluish coloration occurring in roughly one third of reported cases.5 Apocrine hidrocystomas are most commonly found on the head and neck and less commonly on the trunk. It has been suggested that the primary sites of occurrence of these tumors are a reflection of a defective resorptive process of embryologically placed epithelial buds in those areas.6 This theory would explain the infrequent finding of lesions in apocrine gland–bearing regions, such as the axilla, groin, and perineum.
Gradually Enlarging Bilateral Facial Nodules. Arch Dermatol. 2001;137(5):657-662. doi: