Cutaneous ciliated cyst on the finger: a cutaneous mullerian cyst

As previously recognized by various authors, "cutaneous ciliated cyst" is a confusing term. Typically, the term refers to rare cystic lesions, commonly found on the lower limbs of women in their reproductive years. To date, 40 cases diagnosed as "cutaneous ciliated cyst" have been reported in the literature. Histologically, the cysts are composed of a simple layer of ciliated columnar cells along with nonciliated columnar cells, cuboidal cells, and round "peg-like" cells, resembling fallopian tube epithelium. This histology has been described in cysts found in males and females and in locations other than the lower limbs. Controversy has thus arisen over the etiology of these lesions, with some believing that the cysts arise from heterotopic Mullerian rests and others advocating for ciliated metaplasia of eccrine glands. We herein describe the first case of cutaneous ciliated cyst of Mullerian origin occurring on the dorsal thumb of a 16-year-old female. A review of literature shows that 2 groups of cysts are covered under the umbrella term "cutaneous ciliated cysts." We thus propose the abandonment of the confusing term "cutaneous ciliated cyst" and the adoption of "cutaneous Mullerian cysts" for estrogen receptor/progesterone receptor-positive lesions resembling simple fallopian tube epithelium and "Cutaneous ciliated eccrine cyst" for estrogen receptor/progesterone receptor-negative lesions usually occurring in males, which are immunohistochemically compatible with an eccrine origin.