title: A sac-like protrusion on the right upper arm.
authors: Department of Dermatology1, the 251st Hospital of Chinese PLA, Zhangjiakou city, P. R. China.
authors: Li-Qiang
authors: LQ
authors: Zheng
authors: Xiang-Chun
authors: XC
authors: Han
authors: Yong
authors: Y
authors: Huang
authors: Xiao-Dong
authors: XD
authors: Niu
mesh_terms: D000328:Adult; D001132:Arm / Q000473:pathology; D003937:Diagnosis, Differential; D006201:Hair Diseases / Q000473:pathology*; D006801:Humans; D008297:Male; D018296:Pilomatrixoma / Q000473:pathology*; D012867:Skin / Q000473:pathology*; D012872:Skin Diseases, Vesiculobullous / Q000473:pathology*; D012878:Skin Neoplasms / Q000473:pathology*