[Main Types of Cysts in Dermatopathology: Part 2]

This is the second article in a two-part series published in this journal, in which we examine the histopathological characteristics, as well as the differential diagnosis, of the main entities that present as cystic and pseudocystic structures in cutaneous biopsy. In this second article, we address ciliated cutaneous cysts, branchial cysts, Bartholin's cysts, omphalomesenteric cysts, thymic cysts, thyroglossal duct cysts, synovial cysts, and median raphe cysts, as well as mucocele, ganglion, and auricular and digital myxoid pseudocysts.

[Main Types of Cysts in Dermatopathology: Part 1]

Cystic structures represent one of the most common findings in dermatopathology. These encompass both cystic tumors and pseudocysts resulting from the accumulation of certain substances, such as mucin. In a two-part series (of which this is the first part), we have reviewed the principal types of cysts and pseudocysts that may be observed in cutaneous biopsies, examining their histopathological features and primary differential diagnoses. This first part encompasses infundibular cysts, eruptive dermoid cysts, pigmented follicular cysts, pilonidal cysts, tricholemmal cysts, milium cysts, hybrid cysts, bronchogenic cysts, as well as steatocystoma, hydrocystoma, and comedones.

Two Pilosebaceous Cysts with Apocrine Hidrocystoma in One Biopsy Site: A Spectrum of the Same Disease Process?

A 28-year-old woman presented with multiple, asymptomatic, erythematous to bluish papules located on the chest. Histopathologically, three round, well defined cystic structures were seen on the upper and lower dermis. The first cyst was milia, the second was apocrine hidrocystoma and the other, largest cyst was an eruptive vellus hair cyst (EVHC). A diagnosis of multiple pilosebaceous cysts combined with apocrine hidrocystoma was made. Since the milia and EVHC originate from the pilosebaceous unit, and the apocrine duct opens to the pilosebaceous orifice, we suggest that they can occur simultaneously in the same unit.