ABSTRACT. Multiple, pigmented, verrucous, cutaneous lesions in a 2-year-old female cat were pathologically examined. The lesions were linearly arranged on the right side of the body, and had developed along with moderate pruritus since infancy. Histologically, prominent exophytic, papillomatous outgrowths of the epidermis and acanthosis with intense ortho and parakeratotic hyperkeratosis were characteristic of the lesions. Dermal inflammation with mononuclear cells, neutrophils, and eosinophils was also noted. Inclusion bodies, cellular degeneration, and intranuclear viral particles suggesting papillomavirus infection in the keratinocytes were not observed. Papillomavirus antigen and DNA were not detected in the lesions by immunohistochemistry and polymerase chain reaction, respectively. In accordance with these clinical and histopathological features, the cutaneous lesions of the present cat were diagnosed as epidermal nevi, which were consistent with human inflammatory linear verrucous epidermal nevi. Cutaneous papilloma, or verrucous lesions, which are rarely seen in cats, may be caused by viral infections, developmental anomalies, or traumatic stimuli of the skin [5]. The time of onset, gross appearance, and pathological features of the skin lesions are important for differential diagnosis. Two cases of feline cutaneous papilloma associated with papillomavirus (PV) infection have been reported [3,9], although cases of congenital origin have not been described. We report a young cat with multiple, characteristic, linearly arranged, cutaneous, verrucous lesions that had developed during infancy. Pathological features of the lesions did not accord with PV infection, and rather similar to those of inflammatory linear verrucous epidermal nevus (ILVEN), a variant of epidermal nevi in humans [1,7].A 2-year-old female domestic short-haired cat developed multiple, verrucous lesions with erythematous margins arranged in a linear pattern on the right side of the body (Fig. 1). The lesions ranged from 5 mm to 30 mm in diameter and were moderately pigmented, although their surfaces were often light brown. According to the owner, these cutaneous lesions along with moderate pruritus had been observed since infancy. The cat had been reported to present with right-sided ataxia and intention tremor.All masses were surgically removed and tissue samples were fixed in 10% neutral-buffered formalin and embedded in paraffin wax. The sections (4 µm) were cut and stained with hematoxylin and eosin (HE). A standard immunoperoxidase technique was used for the immunohistochemical detection of the PV antigen. The paraffin sections were treated with rabbit polyclonal anti-bovine papillomavirus (BPV-1) antibody (DakoCytomation, Carpinteria, CA, U.S.A.). Before incubation with the primary antibody, the deparaffinized sections were treated with 0.1% trypsin for 1 hr at 37°C. Peroxidase-conjugated anti-rabbit IgG [Histofine Simple Stain MAX-PO (R); Nichirei, Tokyo, Japan] was used as the secondary antibody. The reaction products were visual...