Retroviruses are among the leading causes of death in domestic cats. Retroviruses associate with the host cell in a persistent and permanent way, leading to diverse clinical conditions. The feline leukemia virus (FeLV) is the most pathogenic retrovirus with the potential to cause both degenerative diseases and immunosuppression, as well as proliferative diseases, as its association with the cell may lead to a direct oncogenic effect. The feline immunodeficiency virus (FIV), in turn, can lead to the classic immunodeficiency syndrome, usually has a chronic, less aggressive course and has no direct oncogenic effect. The use of vaccines and control measures has resulted in a decrease in the prevalence of FeLV in the United States of America (USA) and Europe, however, in Brazil, statistics show prevalence rates above 50%. This study aimed to assess the prevalence of feline retroviruses, by immunoenzymatic assay testing, in the region of Grande Vitória, in Espírito Santo and also point out the frequency of neoplasms in these cats. A total of 388 cats were retrospectively evaluated (2014)(2015)(2016). The prevalence of FIV was 2.3% and FeLV was 33.7%. Neoplasms were identified in the three cats seropositive for FIV and FeLV and in three cats infected only with FIV. Neoplasms were also found in 26.6% of cats that were seropositive only for FeLV, especially mediastinal lymphoma. The high prevalence of FeLV demonstrated in this study highlights the need for establishing effective control measures, with emphasis on vaccination.

Background: Primary bone tumours are uncommon and poorly reported in cats but osteosarcoma (OSA) is the most frequent, mostly in elderly animals. Giant cell-rich OSA is considered rare in the literature representing 3% of all OSA in humans. The mitotic index seems to have a significant effect on the survival time of cats affected by this neoplasm as well as the tumour histopathological grade. The objective of this study was to report the cytological and histopathological findings of a giant cell rich OSA in a 4-year old cat with persistent feline leukemia virus (FeLV) antigenaemia.Case: A 4-year-old male neutered cat was referred with a history of persistent FeLV viraemia and pelvic limb lameness with a firm swelling. Previous radiographs of the affected limb revealed bone lysis in the third and fourth metatarsals and increased soft tissue radiopacity in the tarsal region. The referral veterinary assumed it to be osteomyelitis and initiated clinical treatment with antibiotic and anti-inflammatory. The cat was referred after there was no response to medical treatment. The cat was presented with a 5cm diameter ulcerated mass, with putrid odor in the pelvic limb. Complementary exams were performed, and abnormalities were found, including increased urea, creatinine, calcium and potassium, and decreased sodium and phosphorus. A new radiograph showed exuberant bone proliferation, with increased radiopacity involving tarsal, metatarsal, distal third of tarsal I and II, and distal diaphysis of metatarsal V, without compromising the metaphyseal region of distal diaphysis of metatarsal IV. Chest radiographs and abdominal ultrasound were unremarkable. Fine-needle aspiration was performed for cytological analysis, which reavealed a moderate amount of pleomorphic mesenchymal cells with moderate adhesion, cytoplasm with a format ranging from fusiform to stellate, pronounced anisocytosis and cellular pleomorphism, and elevated nucleus:cytoplasm ratio. Nucleus was oval and presented loose chromatin, single to double large and evident nucleolus, frequent karyomegaly, along with marked anisocariosis and nuclear pleomorphism. Multinucleated giant cells were and there was a single mitotic figure in 12 high power fields (0.196 mm2 FN20/400x). Therefore, it was suggestive of malignant mesenchymal neoplasia with possibility of OSA, fibrosarcoma oe undifferentiated sarcoma. Limb amputation with femoral disarticulation was performed uneventfully. The material was conserved in 10% formalin, submitted to macroscopic and microscopic evaluation, which showed a large number of fusiform and stellate cells, with indistinct edges, scarce eosinophilic cytoplasm, high nucleus:cytoplasm ratio and oval nucleus, presenting moderate to marked anisocariosis, loose chromatin, with unique and evident nucleoli, besides of bone trabeculae. Nuclear pleomorphism was moderate and there was four mitotic figures in three random high-power fields (400x). It was observed areas of vascular ectasia, and neoplastic embolization in lymphatic and blood vessels. Among the cells, collagenous stroma was predominant but in some areas there was an eosinophilic amorphous material with the possibility of osteoid matrix or collagen. There was also a large numbers of multinucleated giant cells. The histopathological result was compatible with a grade III giant cell rich OSA.Discussion: Although bone tumours are uncommon in cats, OSA is the most frequent, affecting maingly middle-aged to elderly cats, with a mean age of 10 years, which is different from the present report in a 4-year old cat, with FeLV persistent viraemia. Retroviral status may have influenced the development of the disease at na early onset. FeLV induces uncontrolled cell proliferation through insertional mutagenesis (usually near myc) inducing malignant neoplasias, mainly lymphoma, but also multiple cartilaginous exostosis, which, along with osteomyelitis and bone cyst were included in this patient´s list of differential diagnoses. Despite the macroscopic and radiographical andagressiveness there was no metastasis identified through chest radiographs or abdominal ultrasound, and feline OSA is associated with a lower metastatic rate, if compared to canine OSA. Cytological analysis was compatible with malignant mesenchymal neoplasia, being suggestive of giant cell rich OSA. There is no cytological classification for OSA, however cytological findings of malignancy may be correlated with the patient's clinical course. Cytological features were in agreement with the histopathological findings, compatible with a grade III giant cell rich OSA. Therefore, it is concluded that the characteristics of malignancy presented by cytology were sufficient for the recommendation of amputation of the affected limb, once there was no imaging sign of metastases in the chest or abdomen.

Due to author's honest mistake the article "Retrospective study of retroviruses by immunoenzymatic test on cats in Grande Vitória (ES, Brazil) and associated neoplasms" (DOI