lichen planus ( lp ) is characterized by pruritic polygonal violaceous papules , thought to be the result of an autoimmune reaction to an unknown trigger . lichen planus hypertrophicus ( lph ) is most commonly found over the extensor aspect of lower extremities . coexistence with other dermatoses is probably related to similar etiopathogenesis behind them . on the other hand , epidermal inclusion cyst is the result of plugged pilosebaceous duct and does not have any relation to autoimmunity . we report herein a case of lph on scrotum in association with epidermoid cysts , for its rarity . a 36-year - old man presented to us with very itchy , grayish , elevated swellings over the scrotum present for the preceding 2 years . it started with a yellowish elevated non itchy skin lesion , which gradually turned into extremely pruritic lesion of darker color . , there were multiple grayish to flesh colored , firm plaques with few yellowish nodules over scrotum [ figure 1a and b ] . the excision biopsy specimen revealed a yellowish , firm nodular mass within the substance [ figure 2 ] . histopathology showed compact orthokeratosis , hypergranulosis , marked irregular acanthosis with saw - toothing of rete ridges , band - like lymphocytic infiltrate at the dermo - epidermal junction with areas of basal cell degeneration , accentuated at the base of rete ridges . a cyst was also noted in the mid - dermis , filled with keratin , along with a few foci of calcification [ figures 3 and 4 ] . a diagnosis of isolated scrotal lph with colocalization of epidermoid cyst was made and three intralesional injections of triamcinolone acetonide were administered at 3 weeks interval ; resulting in resolution of lesions of lph , leaving the cysts and areas of hyperpigmentation [ figure 5 ] . multiple grayish to flesh colored , firm papulo - nodules and plaques over the right ( a ) and left ( b ) side of scrotum the excision biopsy specimen showing a yellowish mass within the substance irregular acanthosis , compact orthokeratosis , hypergranulosis . a cyst filled with keratin , is appreciated the mid - dermis , along with a few foci of calcification ( h and e , 40 ) irregular acanthosis with saw - toothing of rete ridges and band - like lymphocytic infiltrate at the dermo - epidermal junction with areas of basal cell degeneration , accentuated at the base of rete ridges . ( h and e , 40 ) posttreatment clinical photograph showing resolution of lesions of lichen planus hypertrophicus , leaving the cysts and areas of hyperpigmentation lichen planus is a common papulosquamous disorder involving the skin , nails , and mucosae . lesions of lph are characterized by hypertrophic verrucous plaques predominantly distributed over the shins or dorsal aspect of feet . histopathology shows marked irregular acanthosis , hypergranulosis , compact orthokeratosis , basal layer degeneration , and the lymphocytic inflammatory infiltrate is accentuated at the base of the rete ridges . epidermoid cysts are keratin - filled epithelial lined cysts , mostly originating from the follicular infundibulum . they classically manifest as dermal or subcutaneous lesions , located on the upper chest , upper back , neck or head . reported associations include gardner 's syndrome , nevoid basal cell carcinoma syndrome , and pachyonychia congenita type 2 . two cases of nevus comedonicus in association with epidermoid cysts were reported . both the cases had multiple nodular swellings scattered within the area of nevus comedonicus , which were confirmed to be epidermoid cysts after histopathological examination . autoimmunity being the basic pathogenetic mechanism behind the development of lp , this has been reported to occur along with vitiligo by many authors . another interesting case was of co - existence of vitiligo , lp , and becker 's nevus . colocalization of lp have also been described with subacute cutaneous lupus erythematosus , generalized morphea , lichen sclerosus , generalized lichen amyloidosis , riehl 's melanosis , and psoriasis . a co - existence of lp and porokeratosis has also been reported in a 40-year - old man . to the best of our knowledge , presentation of lph on scrotum and its colocalization with epidermoid cyst , has not been reported , in the literature . colocalization of lichen planus hypertrophicus and epidermoid cyst that too in scrotum , is not reported yet ; to the best of our knowledge .
colocalization of diseases in dermatology has always remained elusive and a puzzle , difficult to unscramble . 
 co - localization of two rare and disparate dermatoses has been reported on several occasions . 
 lichen planus ( lp ) has been described to colocalize with several dermatoses . 
 we report here a case of lp hypertrophicus co - localizing with epidermoid cysts on the scrotum of a 35-year - old man for the unusual site and association .