koebner described the isomorphic phenomenon in 1872 by reporting the appearance of psoriasis on previously noninvolved skin after skin trauma [ 1 , 2 , 3 ] . besides psoriasis , there is an ever - expanding array of dermatoses that can arise following cutaneous injury . the term true koebnerization describes the reproducible koebner phenomenon induced by an external injury , as observed in psoriasis and lichen planus . the designation pseudo - koebnerization is used for cutaneous infections that can disseminate infectious agents , including warts or molluscum contagiosum . occasional koebnerization is reserved when some criteria for the koebner response are encountered but not always reproducible , like in darier disease , erythema multiforme , granuloma annulare and behet disease . the last category represents the questionable trauma - induced processes , including all the cutaneous disorders reported as case reports that evoke a link to injury , such as pemphigus vulgaris , discoid lupus erythematosus , lupus erythematosus and eruptive xanthoma . mycosis fungoides ( mf ) is the most often encountered type of primary cutaneous t - cell / nk - cell lymphoma ( pctnkcl ) . the precise origin of pctnkcl still remains enigmatic , although some hypotheses are proposed , such as chronic exposure to topical chemical agents   or professional exposure to chemicals . other risk factors for mf are longstanding psoriasis and urticaria , but atopic dermatitis and viral infections seem not to represent risk factors . we present 3 patients with various stages of mf lesions appearing on previously noninvolved skin after cutaneous trauma . a 69-year - old patient with a 4-year history of mf presented the rapid occurrence of a well - circumscribed infiltrated plaque about 2 weeks after the surgical excision of an infundibular cyst in the right retroauricular region ( fig . the patient was on a low - dose maintenance interferon therapy ( introna ; shering - plough , 2  3.10 iu per week ) and presented a clinical stage of t1n0m0b0 . a 3-mm punch biopsy was performed under local anesthesia , and histological analysis confirmed early - stage mf with a high number of atypical lymphocytes infiltrating the epidermis . a monoclonal t - cell receptor rearrangement was evidenced in the sample . as the patient had a stable disease , the dosing of interferon was not increased , and the plaque was treated with very potent topical steroids ( clobetasol propionate 0.05 cream , 1/day , for 4 weeks ) . however , 3 months later , the mf lesion reappeared exactly at the same place with the same clinical aspect . after 2 months of high - dose interferon ( introna , 3  9.10 ui per week ) , the tumoral lesions slunk to slightly infiltrated plaques . the interferon dose was tapered over 4 weeks , and methotrexate maintenance therapy was initiated ( 10 mg per week ) . after a fall , she used a crutch with her right arm due to low back pain . about 1 month after her fall , she presented a tumoral mf - like lesion of the palmar aspect of her right hand . the patient refused to return to interferon therapy as the lesion was not bothering her . topical potent steroids ( clobetasol propionate 0.05 cream , 1/day ) and weekly intralesional infiltrations of corticosteroids ( triamcinolone acetonide 10 mg / ml , albicort ; sanofi - aventis ) were administered with an acceptable clinical regression after 5 weeks . as her condition improved steadily , she refrained from using her crutch , and no recurrence was observed on her hand . a 57-year - old man presented a longstanding history of extensive cutaneous mf ( t2n0m0b0 ) . besides topical steroids , he had previously received several courses of uvb and repuva treatments with good clinical tolerance and results . after a complete remission period of 6 months , he presented again for recurring mf , especially localized at his belt . at this moment , the staging was t1n0m0b0 . curiously , limited at a friction zone on his right hip due to his belt , he presented serpiginous infiltrated and erythematous lesions ( fig . he had never observed this phenomenon previously . he had not received a local traumatism . as the patient did not present at that time more than 10 skin lesions , it was decided to treat him by very potent topical corticosteroids ( clobetasol propionate 0.05 cream , 1/day ) . after approximately 4 weeks a 69-year - old patient with a 4-year history of mf presented the rapid occurrence of a well - circumscribed infiltrated plaque about 2 weeks after the surgical excision of an infundibular cyst in the right retroauricular region ( fig . the patient was on a low - dose maintenance interferon therapy ( introna ; shering - plough , 2  3.10 iu per week ) and presented a clinical stage of t1n0m0b0 . a 3-mm punch biopsy was performed under local anesthesia , and histological analysis confirmed early - stage mf with a high number of atypical lymphocytes infiltrating the epidermis . a monoclonal t - cell receptor rearrangement was evidenced in the sample . as the patient had a stable disease , the dosing of interferon was not increased , and the plaque was treated with very potent topical steroids ( clobetasol propionate 0.05 cream , 1/day , for 4 weeks ) . however , 3 months later , the mf lesion reappeared exactly at the same place with the same clinical aspect . a 51-year - old woman presented with tumoral mf ( t3n0m0b0 ) . after 2 months of high - dose interferon ( introna , 3  9.10 ui per week ) , the tumoral lesions slunk to slightly infiltrated plaques . the interferon dose was tapered over 4 weeks , and methotrexate maintenance therapy was initiated ( 10 mg per week ) . after a fall , she used a crutch with her right arm due to low back pain . about 1 month after her fall , she presented a tumoral mf - like lesion of the palmar aspect of her right hand . the patient refused to return to interferon therapy as the lesion was not bothering her . topical potent steroids ( clobetasol propionate 0.05 cream , 1/day ) and weekly intralesional infiltrations of corticosteroids ( triamcinolone acetonide 10 mg / ml , albicort ; sanofi - aventis ) were administered with an acceptable clinical regression after 5 weeks . as her condition improved steadily , she refrained from using her crutch , and no recurrence was observed on her hand . a 57-year - old man presented a longstanding history of extensive cutaneous mf ( t2n0m0b0 ) . besides topical steroids , he had previously received several courses of uvb and repuva treatments with good clinical tolerance and results . after a complete remission period of 6 months , he presented again for recurring mf , especially localized at his belt . at this moment , the staging was t1n0m0b0 . curiously , limited at a friction zone on his right hip due to his belt , he presented serpiginous infiltrated and erythematous lesions ( fig . a 3-mm punch biopsy was taken to exclude psoriasis induced by the koebner phenomenon . however , histology confirmed early - stage mf . as the patient did not present at that time more than 10 skin lesions , it was decided to treat him by very potent topical corticosteroids ( clobetasol propionate 0.05 cream , 1/day ) . the 3 cases described here are probably best classified in the third category of occasional koebner phenomenon . in the psoriasis literature , it has been described that scar sites are particularly prone to the koebner effect , related to the changes in local vascularization and neoangiogenesis . psoriasis disease severity seems not to present a risk factor , but stress factors do . the precise pathogenic understanding of koebner phenomenon remains enigmatic , but probably a whole array of stress proteins , cytokines , neuromediators including nerve growth factor , growth factors like basic fibroblast growth factor and adhesion molecules are certainly intervening . it is hypothesized that the atypical mf cells usually displaying a cd3 + , cd4 + , cd8 and cd45r0 + phenotype , and a th2 cytokine production profile , find a favorable environment for disease induction , activation or reactivation . a recent report described 4 patients developing mf on previously traumatized skin sites . all these patients were male and presented a median time of 10 years between the cutaneous traumatism and the diagnosis of mf . the transdermal estradiol patch - restricted mf   and solvent - induced tumor d'emble mf   are probably related to the chronic exposure to chemical agents . although traumatic in origin , the very long time interval between traumatism and the occurrence of mf does not correspond to the definition of a koebner effect . in sum , these case presentations suggest that mf early stage and tumoral stage lesions may point to the koebner phenomenon . this study was performed in accordance with the ethics standards of the university hospital committee on institutional human experimentation and with the declaration of helsinki of 1975 , as amended in 1983 . the aims of the study were explained to all the patients , and all signed an informed consent .
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 .