Cytomorphological and immunological classification of feline lymphomas: clinicopathological features of 76 cases.

Of the various classification systems for non-Hodgkin's lymphoma, the updated Kiel classification is valuable for veterinary practice, because of its utility to classify the subtypes not only by histopathology but also by cytomorphology. However, there are only a few reports of small number of feline lymphomas to apply the updated Kiel classification. In this study, immunogical subtypes and morphology of 76 feline lymphomas were evaluated and classified into subtypes of the updated Kiel classification. Of the cases, 49% were T-cell lymphoma, 25% were B-cell lymphoma and 26% were undetermined immunological subtype. Based on the updated Kiel classification, most subtypes were identified also in feline lymphomas as in dogs and humans. Globule leukocyte lymphoma was specific for cats and relatively common in feline alimentary lymphomas. Of the present cases, 64% were high-grade subtypes, whereas 36% were low-grade subtypes. The present study indicated that feline lymphomas could be morphologically classified by the modified updated Kiel classification.

Feline epidermal nevi resembling human inflammatory linear verrucous epidermal nevus.

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.

A case of canine vasotropic and vasoinvasive nonepitheliotropic lymphoma with unusual tumor cells and extensive dermal necrosis.

A 14-year-old, spayed female Shih-tzu dog presented with masses in the dorsal aspect of cervical region and digit of the right anterior limb. Extensive necrosis was seen in the dermal tissue overlying the tumor, and diffuse round cell proliferation and infiltration were seen histologically from the superficial dermis to the deep dermis. Two types of proliferating cells were present: lymphoblast-like cells with round-oval, vesicular nuclei and moderate-large nucleoli; and smaller cells with characteristic irregularly shaped nuclei. Electron microscopy of these smaller cells showed cerebriform, pleomorphic nuclei with a chromatin pattern characteristic of lymphoid cells, as seen in lymphoblast-like tumor cells. Immunohistochemically, both types of tumor cells were positive for CD3. Most vessel walls had been invaded by tumor cells, resulting in extensive dermal necrosis and hemorrhage. Based on these histopathological findings, the tumor was diagnosed as vasotropic and vasoinvasive nonepitheliotropic lymphoma, characterized by a notable presence of unusual tumor cells with irregularly shaped nuclei and extensive dermal necrosis.