Trichilemmal cysts, also known as pilar cysts or tricholemmal cysts, are derived from the outer root sheath of the deeper parts of a hair follicle and consist of a well-keratinized epidermal wall surrounding semisolid hair keratin. They occur ... Trichilemmal cysts, also known as pilar cysts or tricholemmal cysts, are derived from the outer root sheath of the deeper parts of a hair follicle and consist of a well-keratinized epidermal wall surrounding semisolid hair keratin. They occur predominantly on the scalp, are easily enucleated, and appear as a firm, smooth, white-walled cyst without a punctum (McGavran and Binnington, 1966; Pinkus, 1969; Leppard and Sanderson, 1976).
Eiberg et al. (2005) reported a Danish family in which 11 members had trichilemmal cysts inherited in an autosomal dominant pattern. The cysts most often appeared in adolescence, only occurred on the scalp, were predominantly solitary, and only ... Eiberg et al. (2005) reported a Danish family in which 11 members had trichilemmal cysts inherited in an autosomal dominant pattern. The cysts most often appeared in adolescence, only occurred on the scalp, were predominantly solitary, and only numerous in 2 cases. Seidenari et al. (2013) retrospectively reviewed 149 surgically excised and histologically confirmed trichilemmal cysts, of which 24 cases were familial. Construction of family pedigrees was consistent with autosomal dominant inheritance. There was a younger age of onset and greater presence of multiple cysts in hereditary cases compared to sporadic cases; however, there was no difference in site of occurrence between familial and sporadic cysts. Two patients with familial trichilemmal cysts had associated malignancies: the first had colorectal adenocarcinoma and melanoma, whereas the second had renal cell carcinoma and prostate adenocarcinoma. Seidenari et al. (2013) proposed the following clinical criteria for identification of hereditary cases: diagnosis of trichilemmal cysts in at least 2 first-degree relatives, or in 3 first- or second-degree relatives in 2 consecutive generations; trichilemmal cysts diagnosed at less than 45 years of age in at least 1 family member; and the diagnosis of multiple cysts, giant cysts (greater than 5 cm), or cysts with rare histopathologic features, such as proliferation or ossification. The authors noted that the clinical suspicion of hereditary disease would result in earlier diagnosis and screening of younger family members, with a correspondingly reduced risk of malignant transformation.