Atheroma Derived from the root sheath of the hair follicle. Globular, elastic, mobile tumor covered with atrophic thin skin, thick wall, filled with keratin, is not connected to the epidermis, and is without external opening. Tender if infected. Baldness over large cyst skin due to follicular pressure damage. No inflammation or proliferation from trauma. No malignant degeneration
Pilar cyst, trichilemmal cyst Archaic names: Wen
>90% Scalp, hair follicle epithelium
Retention cyst Spherical, mobile, firm under tense skin. Ruptures easily by manipulation. Keratinous material can be pressed into the surrounding tissue and then acts as a foreign body and can cause granuloma abscess formation from bacterial infection.
Milia, acne cysts, and traumatic inclusion cysts
Face, trunk, hair follicles areas, scalp, neck, back, and cheeks One millimeter to several centimeters in diameter Cutaneous or subcutaneous—fluctuant, easily movable, tense, swelling Expanded gland duct and foul-smelling rancid lipids and debris will reoccur if wall remains intact.
Sebocystomatosis Central opening exudes a pasty, cheesy odoriferous material composed of keratin and lipid-rich debris
Sebaceous cysts (fat)
Young-middle-aged adults. Scalp, face, neck, upper trunk, scrotum, and vulva
Keratinous cyst Firm, movable, globular, and nontender unless infected. Contents are soft and yellow-white, with a rancid odor
Epidermal and sebaceous
Face, neck, and upper trunk, almost any area of the body
Milium Primary milia arise spontaneously and are keratin filled. Secondary milia arise in pilosebaceous glands or within damaged eccrine sweat gland ducts following subepidermal bulla formation (e.g., epidermolysis bullosa, porphyria cutanea tarda, bullous pemphigoid) or skin radiotherapy. Primary and secondary milia are identical histologically.
Eyelids, forehead, and cheeks Young to middle-aged men and women and infants Tiny (1-2 mm), superficial, white dome-shaped cysts
Dermoid cyst Present at birth
Deep subcutaneous tissue Walls composed of keratinizing epidermis containing hair follicles, sebaceous glands, and sweat glands
Epidermoid cyst Occurs secondary to traumatic implantation of epidermal cells into the dermis. Contains accumulation of keratin and is encased by a well-formed granular layer of stratified squamous epithelium
Epidermal inclusion cyst
Most common on face, back, chest and base of ears although can occur on almost any skin surface.
Adapted from Goldstein, B. G., & Goldstein, A. O. (2014a). Overview of benign lesions of the skin. Retrieved 27 March, 2014 from www.uptodate.com/contents/overview-of-benign-lesions-of-the-skin?source=search_result&search=calluses&selectedTitle=2%7E16#H1101420580; Goldstein, B. G., & Goldstein, A. O. (2014b). Keloids. Retrieved 23 April, 2014 from www.uptodate.com/contents/keloids?source=search_result&search=keloid+scar&selectedTitle=1%7E150; Wolff, K., Johnson, R. A., & Saadvedra, A. P. (2013). Fitzpatrick’s color atlas & synopsis of clinical dermatology (5th ed.). New York, NY: McGraw-Hill; Habif, T. P. (2016). Clinical dermatology: A color guide to diagnosis and therapy Philadelphia, PA: Elsevier.