Abstract: Wu Lei *, Wu Jian, Chen Lingling, Cai Meihong, Chen Xiaojian, Wang Feng, Zeng Xuesi. *Department of Dermatology and Venereology, Affiliated Suzhou Municipal Hospital of Nanjing Medical University, Suzhou 215006, China Corresponding author: Chen Lingling, Email: chenlingling031@126.com 【Abstract】 A 44-year-old male presented with a neoplasm on the buccal side of the right nasolabial fold for more than two months. Dermatological examination showed a hemispherical bulge sized 1.5 cm × 1.5 cm with central crater-like ulceration on the buccal side of the right nasolabial fold, as well as a crescent-shaped elevation measuring 1.5 cm × 2.5 cm above the hemispherical lesion. Histopathology of the hemispherical lesion revealed irregularly downward proliferation of epidermis, crater-like holes filled with eosinophilic keratinous plug in the center which were surrounded by collar-shaped epithelial cell projections. Small neutrophil abscesses were found in the clumps of epithelial cells, and massive lymphocyte infiltration with a clear bottom boundary was observed around the proliferating epithelial cells. Histopathologic examination of the crescent lesion showed multiple irregularly-shaped lobular-like structures of various sizes with sebaceous glands at different degrees of maturity in the mid dermis, which were surrounded by proliferating connective tissue. Immunohistochemical studies showed that the squamous cells stained positive for cytokeratin （CK）, CK5, CK14, CK17, carcinoembryonic antigen （CEA） and epithelial membrane antigen （EMA） in the keratoacanthoma, and the sebaceous cells for CK, CK5, CK14 and EMA in the sebaceous adenoma. The pathological diagnosis was keratoacanthoma and sebaceous adenoma. The patient was diagnosed with moderately and poorly differentiated rectal adenocarcinoma in 2008. A diagnosis of Muir-Torre syndrome presenting as keratoacanthoma and sebaceous adenoma was finally made.

Key words: Muir-Torre syndrome, Keratoacanthoma, Sebaceous gland neoplasms