Cystic Tricholemmal Carcinoma In Situ

Abstract

An 89-year-old man presented with a clinically cystic 4-mm papule on the left temple. The clinical impression was a benign cyst. Pathologic examination revealed a small, symmetric-appearing, well-circumscribed, dermal-based cystic lesion with markedly atypical-appearing clear to squamoid cells lining the cyst wall, consistent with carcinoma in situ involving the cyst. The cells showed abundant glycogen-containing cytoplasm (confirmed by Periodic acid Schiff stains with and without diastase), consistent with tricholemmal differentiation, and areas of tricholemmal/pilar-type keratinization (without a granular layer), consistent with tricholemmal carcinoma in situ, most likely arising in a tricholemmal/pilar cyst. Ki-67 and p53 immunohistochemical stains were strongly positive (with more than 20% of nuclei staining on Ki-67 and more than 80% on p53) in the cyst-lining cells, further supporting the interpretation of carcinoma in situ. Multiple deeper level sections were examined but did not show any evidence of an associated invasive carcinoma. Tricholemmal (pilar) cysts are common benign adnexal lesions and atypia/dysplasia or carcinoma in situ arising within them is exceedingly rare. Previously, only one case of a tricholemmal cyst with carcinoma in situ has been reported. That case was associated with an atypical fibroxanthoma. We report only the second case of tricholemmal carcinoma in situ, most likely involving a tricholemmal cyst, which was not associated with another tumor or evidence of invasive carcinoma.

In situ carcinoma in a hybrid cyst: a case report

“…Most of the lining cells exhibited trichilemmal characteristics, marked cytological atypia, pleomorphism and numerous mitotic figures, diagnosed as in situ cystic trichilemmal carcinoma. This case also had focal overlying epidermal changes suggestive of actinic keratosis and solar lentigo, but was not associated with invasive carcinoma or any other tumor . In addition, Arsenovic et al reported the case of a 91‐year‐old woman with a solitary skin nodule on the forehead.…”

“…Neoplasms in the squamous epithelium, squamous papilloma and squamous cell carcinoma have been previously described in cutaneous epidermal or trichilemmal cysts . Moreover, two cases of in situ carcinoma in a cyst with trichilemmal with epithelium different histological features have been reported.…”

“…Neoplasia in a cyst varies, with previous reports describing in situ carcinoma in a trichilemmal cyst, 9,10 high-grade intra-epithelial neoplasia in an epidermoid cyst, 11 Bowen's disease in keratinous cysts, 12 in situ carcinoma in an epidermal cyst, 13 in situ Merkel cell carcinoma in a trichilemmal cyst, 15 and squamous cell carcinoma. 16 Andersen et al described four cases of cutaneous epidermoid cysts having an epithelial lining composed of apocrine cells, localized either on the nipple or face.…”

“…Follicular hybrid cysts are rare, and contain two or more components of the epithelial skin adnexa . The remnants of many hair follicles and neoplasia can be seen in hybrid cysts . Moreover, squamous cell carcinoma, high‐grade intraepithelial neoplasia (in an epidermoid cyst), Bowen's disease (in keratinous cysts), in situ carcinoma (in an epidermal cyst), in situ Merkel cell carcinoma (in a trichilemmal cyst), in situ trichilemmal carcinoma, in situ carcinoma (in a trichilemmal cyst), and epithelium composed of apocrine cells have been previously reported in the literature.…”

“…2 -8 The remnants of many hair follicles and neoplasia can be seen in hybrid cysts. 4,6 -15 Moreover, squamous cell carcinoma, 16 high-grade intraepithelial neoplasia (in an epidermoid cyst), 11 Bowen's disease (in keratinous cysts), 12 in situ carcinoma (in an epidermal cyst), 13 in situ Merkel cell carcinoma (in a trichilemmal cyst), 15 in situ trichilemmal carcinoma, 9 in situ carcinoma (in a trichilemmal cyst), 10 and epithelium composed of apocrine cells 4 have been previously reported in the literature. The human papilloma virus (HPV) common antigen and HPV DNA types 57 and 60 have also been identified in a trichilemmal cyst and in a hybrid cyst, respectively.…”