Mycosis fungoides (MF) is the most frequent type of primary cutaneous 
T-cell/NK-cell lymphoma. The Koebner phenomenon is defined as the appearance of 
cutaneous lesions on previously noninvolved skin following trauma and is 
observed in a series of cutaneous diseases including psoriasis, lichen planus, 
viral warts, molluscum contagiosum, etc. In this case report, 3 patients with 
longstanding MF are presented, the 1st with the appearance of a circumscribed 
early-stage type MF lesion rapidly following a surgical excision of an 
infundibular cyst, the 2nd with the appearance of a unique unilateral palmar 
tumoral MF lesion at the pressure site of a crutch, and the 3rd presented 
localized MF early stage lesions at the friction site of a belt. This report 
suggests that some MF patients may experience Koebner phenomenon-induced MF 
lesions and that MF should be added to the long list of skin diseases 
potentially exhibiting the Koebner phenomenon.