Could EMA and cytokeratin 7 be useful in distinguishing tricholemmal carcinoma from clear-cell squamous cell carcinoma? A case series from our department and a brief review of the literature

• Published in: Acta histochemica 2019-08, Vol.121 (6), p.765-767
• Main Authors: Ricci, Costantino, Dika, Emi, Di Nanni, Doriana Donatella, Zannetti, Guido, Lambertini, Martina, Corti, Barbara
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Carcinoma, Squamous Cell - classification; Carcinoma, Squamous Cell - diagnosis; Carcinoma, Squamous Cell - metabolism; Carcinoma, Squamous Cell - pathology; Clear-cell squamous cell carcinoma; Diagnosis, Differential; E2F6 Transcription Factor - metabolism; Female; Humans; Immunohistochemistry; Keratin-7 - metabolism; Male; Neoplasm Proteins - metabolism; Skin Neoplasms - classification; Skin Neoplasms - diagnosis; Skin Neoplasms - metabolism; Skin Neoplasms - pathology; Tricholemmal carcinoma
• ISSN: 0065-1281; 1618-0372
• DOI: 10.1016/j.acthis.2019.06.002

Tricholemmal carcinoma is a malignant cutaneous adnexal tumor showing outer root sheath differentiation, thought to be the malignant counterpart of trichilemmoma. Although the real existence of tricholemmal carcinoma continues to be a matter of debate, it has been introduced in the recently published 4th edition of World Health Organization classification of skin tumors. Herein, we evaluated whether immunohistochemistry (EMA, CK7, CK5/14, p63, p16, and Ber-EP4) supports tricholemmal carcinoma as a separate entity and whether it could be useful in this differential diagnosis. A total of 9 cases, 3 tricholemmal carcinomas and 6 clear-cell squamous cell carcinomas were evaluated on the basis of histological criteria suggested by the WHO. In our opinion, although these results need to be validated in larger series, they support tricholemmal carcinoma as a separate entity and suggest an immunohistochemical profile (clear-cell squamous cell carcinomas: EMA diffusely positive, CK7 negative; tricholemmal carcinoma: EMA negative, CK7 patchy or moderately positive) that could be useful for this differential diagnosis.