Principal findings include an eight-year old unilaterally cryptorchid boar pig with an interstitial (Leydig's) cell tumor who presented with a life-long history of linear preputial dermatosis/erythema and a sudden onset of a space-occupying lesion in the scrotal region. The mass was surgically excised without complication, resulting in gradual recession of the linear preputial dermatosis/erythema over a five month period. Testicular tumors in the boar pig is a rare occurrence and, to the author's knowledge, this is the first report describing a boar pig who exhibited the linear preputial dermatosis/erythema only described in the canine species associated with testicular tumors.