Skin, Trichilemmal cyst

Trichilemmal cysts are the second most common type of cutaneous cyst and occurs on the scalp up to 90% of the time. They tend to occur in adults and can be treated with simple excision. Typically, and in this case, the microscopic appearance is that of a circumscribed simple cyst filled with dense eosinophilic keratin. The epithelium is stratified squamous epithelium lacking a granular layer. Large polygonal keratinocytes with abrupt keratinization are present. Calcification can be present in 25% of cases and is present in this case. Also, trichilemmal cysts may rupture and generate a granulomatous response. In this case, the cyst has ruptured and there are foci of multinucleate giant cells.

See related content for references:

1) Leppard, BJ., et al. Br J Dermatol. 1976 Apr;94(4):379-90.
2) Tellechea, O., et al. An Bras Dermatol. 2015 Nov-Dec;90(6):780-96