Figure 13-9 Cutaneous amyloid in a patient with multiple myeloma. Note the waxy elevation and the associated purpura of

the lower eyelid. (Courtesy of John B. Holds, MD.)

Table 13-2

Cysts

Epidermoid and Dermoid Cysts

Epidermoid cysts, also known as epidermal inclusion cysts, are common in the eyelids. They may arise spontaneously or as a result of the entrapment of epidermis beneath the skin surface following traumatic laceration or surgical incision. Epidermoid cysts are lined with stratified squamous

keratinizing epithelium and contain keratin (Fig 13-10). Dermoid cysts (discussed earlier in this chapter) are similar to epidermoid cysts histologically, but they have skin adnexal structures such as hair follicles and sebaceous glands in the wall. The lumen contains hair and sebum in addition to keratin.

Ductal Cysts

Within the eyelid are the ducts of numerous structures, including the apocrine and eccrine sweat glands and the lacrimal gland. Any of these ducts may give rise to 1 or more cysts. Ducts are typically lined with a double layer of cuboidal epithelium, as are ductal cysts. The lumen of the cyst typically appears empty histologically. Cysts arising from sweat ducts are referred to as either apocrine or eccrine hidrocystomas (Fig 13-11). A cyst arising from the duct of the lacrimal gland is called a dacryops.

Figure 13-10 An epidermoid, or epidermal inclusion cyst, is present in the dermis. The cyst lining resembles epidermis, and

the lumen contains keratin. (Courtesy of Nasreen A. Syed, MD.)