Pulmonary and mediastinal metastases of a vaccination-site sarcoma in a cat

Microvascular Density, Endothelial Area, and Ki-67 Proliferative Index Correlate Each Other in Cat Post-Injection Fibrosarcoma

Soft tissue sarcomas are a large group of different tumor types both in humans and in animals. Among them, fibrosarcoma is the most frequent malignant mesenchymal tumoral form in cats, representing up to 28% of all cat skin tumors, while human fibrosarcoma, fortunately, only represents 5% of all sarcomas and 0.025% of the world-wide burden of tumors. This low incidence in humans leads to consideration of this group of tumoral diseases as rare, so therapeutic options are few due to the difficulty of starting clinical trials. In this context, the identification of research models for fibrosarcomas could be of great interest to deepen knowledge in this field and recognize new or possible biological pathways involved in tumor progression and metastasis. Angiogenesis is considered a fundamental scattering cause of tumor aggressiveness and progression in all forms of cancer, but only a few research parameters were developed and reported to express them quantitatively and qualitatively. The role in angiogenesis of microenvironmental stromal cells, such as fibroblasts, lymphocytes, mast cells, and macrophages, was largely demonstrated since this topic was first approached, while quantification of new vessels and their blood capacity in tumoral area is a relatively recent approach that could be well developed thanks to expertise in immunohistochemistry and image analysis. In this paper, a crossing study evaluating microvascular density (MVD), endothelial area (EA), and Ki-67 proliferative index was reported for a series of formalin-fixed and paraffin-embedded tissue samples from 99 cat patients, affected by cat post-injection fibrosarcoma, by using a till ×400 magnification light microscopy. We aim to demonstrate that cat pets may be considered a useful animal model for better studying the correspondent human diseases and we report, for the first time to our knowledge, experimental data in terms of correlation among MVD, EA, and Ki-67 strictly involved in aggressiveness and tumoral progression.

Description of a Feline Injection-Site Fibrosarcoma with Metastasis in the Cerebellum

Feline injection-site sarcomas were initially described by Hendrick and Goldschmidt (1991). The link between vaccination site and sarcoma occurrence suggested the term of vaccine-associated sarcomas. Our paper describes an unusual feline injection-site fibrosarcoma with cerebellar metastasis. A 7-year-old female domestic short-hair cat was submitted to the Pathology Department (Faculty of Veterinary Medicine Cluj- Napoca, Romania) for necropsy. A subcutaneous tumor (relapse) in the interscapular region and multiple metastatic masses in the lungs, kidneys, subcutaneous tissue (scapular and thigh regions) and cerebellum were observed. Cytological, histological and immunohistochemical (for vimentin, desmin, multi-cytokeratin, α-smooth muscle actin, S100 and CD45) analyses from all tumors were performed. Cytological examination identifi ed highly pleomorphic spindle-shaped cells admixed with neoplastic multinucleated giant cells. Histologically, all neoplastic masses were composed of numerous spindle cells arranged into interlacing bundles. Extensive intratumoral areas of necrosis along with a neutrophilic infiltrate were also detected. A fibrillary material was present among neoplastic cells (green stained by Masson’s trichrome method), suggesting a collagenous structure. In all tumors assessed, immunohistochemistry showed an intense reaction only for vimentin in numerous neoplastic cells. Based on the history, gross, cytological, histological and immunohistochemical data, the final diagnosis was recurrent feline injection-site fibrosarcoma, with multiple metastases (including in the cerebellum). Overall, an uncommon case of feline injection-site fibrosarcoma has been reported. This is the first consistent record of an injection site sarcoma in a cat with cerebellar metastasis.

Curative-intent radical en bloc resection using a minimum of a 3 cm margin in feline injection-site sarcomas: a retrospective analysis of 131 cases

Objectives

Owing to its highly infiltrative growth, feline injection-site sarcoma (FISS) carries a significant risk of local tumour recurrence. Parameters of possible prognostic significance (eg, tumour size and location, resection of de novo vs recurrent tumours, and achievement of tumour-free surgical margins) were examined with regard to their influence on recurrence rate (RR), disease-free interval (DFI) and survival time (ST).

Methods

This was a retrospective analysis of cats with FISSs located on the chest or abdominal wall or the interscapular region treated in a single institution using a standardised radical resection technique with 3 cm lateral margins and full-thickness body wall resection (tumours over chest/abdominal wall) or a minimum of two fascial planes (interscapular tumours).

Results

Median postoperative DFI and ST of 131 cats with FISSs was 21 and 24 months, respectively. Patients operated on for recurrent tumours were significantly more likely to die from tumour-related reasons compared with patients with de novo tumours ( P <0.001). RR and DFI in the different tumour locations were comparable ( P = 0.544 and P = 0.17, respectively). Local tumour recurrence occurred in 38.1% of the cats. Cats operated on for tumour recurrences had a significantly higher chance of another recurrence (RR 55.5% vs 33.3%; P = 0.005). Completeness of excision was determined by taking tumour bed biopsies. Tumour bed biopsies that did not contain tumour cells were associated with a significantly lower RR compared with those with tumour cells (30.5% vs 76.2%).

Conclusions and relevance

Depending on prognostic factors such as surgery for primary vs recurrent tumour, tumour-free resection margins and tumour location, the RR in FISS ranges from 33–55%, despite curative intent radical surgery. This study may help in identifying patients at risk for recurrence.

Origins of injection-site sarcomas in cats: the possible role of chronic inflammation-a review

The etiology of feline injection-site sarcomas remains obscure. Sarcomas and other tumors are known to be associated with viral infections in humans and other animals, including cats. However, the available evidence suggests that this is not the case with feline injection-site sarcomas. These tumors have more in common with sarcomas noted in experimental studies with laboratory animals where foreign materials such as glass, plastics, and metal are the causal agent. Tumors arising with these agents are associated with chronic inflammation at the injection or implantation sites. Similar tumors have been observed, albeit infrequently, at microchip implantation sites, and these also are associated with chronic inflammation. It is suggested that injection-site sarcomas in cats may arise at the administration site as a result of chronic inflammation, possibly provoked by adjuvant materials, with subsequent DNA damage, cellular transformation, and clonal expansion. However, more fundamental research is required to elucidate the mechanisms involved.

Intradermal DNA vaccination in ear pinnae is an efficient route to protect cats against rabies virus

A DNA vaccine against rabies (pGQH) was administrated to cats in order to examine different administration routes. Four groups of three cats each were inoculated with pGQH as follows: group A, intramuscularly (IM), 100 microg; group B, intranasally (IN), 100 microg; group C, intradermally into ear pinnae (ID-EP), 100 microg, and group D, IM, 200 microL of phosphate buffer solution (PBS) alone (control group). Blood was drawn on days 0, 30, 60, 90, 120, 150, and 180. Groups A, B, and C received a booster on day 30. At day 200 all animals were challenged. A passive transfer of cat sera, as well as a viral challenge, was performed in mice. The results displayed that neutralizing antibody titers were higher in cats of group C (ID-EP) showing high early titers (> 2 IU) and the highest titer was on day 120 (> 14 IU). In group B (IN), two out of three cats seroconverted on day 30 (> 0.5 IU), the third cat seroconverted until day 60 (> 0.5 IU). In contrast, the lowest levels of neutralizing antibodies were detected in group A (IM). The control group showed no anti-rabies antibodies. Groups A (IM) and D (control) succumbed after lethal challenge. All animals from the ID-EP group (C) survived, only one individual from the IN (B) group died. Mice that received cat sera from ID-EP, IM, and IN groups survived and were protected (30/30 survivors). Mice groups that received pre-immunization sera from cats were not protected (0/30 survivors). This study demonstrates that pGQH immunization was successful when it was administrated ID-EP, and acceptable through the IN route. The IM route, however, was not effective in cats. For vaccination, the IN route seems attractive due to its accessibility for application, but it seems to activate seroconversion slowly. The best route to promote anti-rabies antibody titers was the ID-EP route. This practical and efficient route should be further studied.

Comparison of the histology and immunohistochemistry of vaccination-site and non-vaccination-site sarcomas from cats in New Zealand

AIMS

To compare the histology and immunohistochemistry of vaccination-site sarcomas (VSSs) with non-vaccination-site sarcomas (NVSSs) in cats in New Zealand. To determine whether VSSs in cats in New Zealand have similar histological and immunohistochemical features to those previously described in feline vaccine-associated sarcomas (VASs) in North American studies.

METHODS

A retrospective survey of skin biopsies submitted between 2004 and 2006 was performed to identify cutaneous sarcomas from both vaccination and non-vaccination sites in cats. Vaccination sites included the interscapular, shoulder, or dorsal or lateral cervical and thoracic regions. All sarcomas were examined histologically, and smooth muscle actin and desmin were assessed immunohistochemically. Features previously described in VASs were assessed and compared.

RESULTS

Sarcomas from 34 cats were identified, 10 of which occurred at vaccination sites. Compared with NVSSs, VSSs were more likely to be located in the hypodermis and have greater cellular pleomorphism, higher mitotic rates, more frequent peripheral lymphocytic aggregates and multinucleated giant cells. VSSs were also more likely than NVSSs to show partial myofibroblastic differentiation, demonstrable using immunohistochemistry. The histological and immunohistochemical features of VSSs in cats in New Zealand are consistent with those previously described in VASs in cats in North America.

CONCLUSIONS

The results of this study suggest that VASs occur in cats in New Zealand.

CLINICAL RELEVANCE

The occurrence of VASs in cats in New Zealand would provide further support for restriction of the vaccination of cats to the minimum necessary to protect health, and adoption of the New Zealand Veterinary Association guidelines on vaccination.

Experimental immunization of cats with a recombinant rabies-canine adenovirus vaccine elicits a long-lasting neutralizing antibody response against rabies

During the past decade, human rabies caused by cats has ranked the second highest in China. Several recombinant rabies vaccines have been developed for dogs. However, seldom have these vaccines been assessed or used in cats. In this trial, we report the experimental immunization of a recombinant canine adenovirus-rabies vaccine, CAV-2-E3Delta-RGP, in cats. Thirty cats were inoculated with the recombinant vaccine intramuscularly, orally and intranasally, respectively. Safety and efficacy studies were undertaken using the fluorescent antibody virus neutralization (FAVN) test and evaluated. Results showed that this recombinant vaccine is safe for cats as demonstrated by the three different routes of administration. The vaccine stimulated an efficient humoral response in the vaccinated cats when 10(8.5)PFU/ml of the recombinant vaccine was injected intramuscularly in a single dose. The neutralizing antibody level increased above 0.5IU/ml at 4 weeks after the vaccination. The mean antibody level ranged from 0.96+/-0.26 to 4.47+/-1.57IU/ml among individuals, and the antibody levels were elicited for at least 12 months. After this period, the immunized cats survived the challenge of CVS-24 and an obvious anemnestic and protective immune response was stimulated after the challenge. The immune response occurred later than the inactivated vaccine and the overall antibody level in the vaccinated cats was lower, but it was sufficient to confer protection of cats against infection. This demonstrated that a single, intramuscular dose of CAV-2-E3Delta-RGP stimulated a long-lasting protective immune response in cats and suggested that CAV-2-E3Delta-RGP could be considered as a potential rabies vaccine candidate for cats.

Feline injection site-associated sarcoma: Is it a reason to critically evaluate our vaccination policies?

Feline injection site-associated sarcoma (FISAS) or vaccination-associated sarcoma is a serious problem in cats because of the ethical and therapeutic consequences associated with the disease. The exact aetiology of FISAS is unclear; therefore, instituting preventative measures such as delaying or discontinuing vaccination schedules is questionable. This paper will give insights into the disease process, will attempt to answer the question, "what causes FISAS?", and will discuss preventative measures to decrease the chance of occurrence. Tumours are in general uncommon in the cat, however, malignant tumours, such as sarcomas, occur relatively frequently. FISAS have stimulated interest because of their reported linkage to certain types of vaccine. FISASs are reported to have an incidence of 1-10 per 10,000 cats and often appear in conjunction with a traumatic incident (such as a vaccination). The tumour displays an extreme malignant biological behaviour, both being locally aggressive and metastasising in 25-70% of the cases. Although the pathology still remains unclear, an exaggerated inflammatory/granulomatous response seems to be the predisposing factor in the transformation to FISAS. A multi-step carcinogenesis model, including genetic, iatrogenic and local factors seems to be the most plausible explanation for the occurrence of the tumour. Multi-modal therapy, based on aggressive surgical removal of the tumour in combination with radiation and/or chemotherapy, is usually recommended but randomised clinical studies have not yet been performed to prove the efficacy of any of the modalities. The question of whether FISAS can be prevented by not injecting irritant products remains unanswered. No specific brands of vaccine, manufacturers or factors associated with vaccine administration have been significantly associated with FISAS in a multi-institutional and epidemiological study. Control and evaluation measures as recommended by the US-based taskforce include determination of risk groups, extending re-vaccination intervals, the use of single component products and the use of consistent, predetermined sites for vaccination.

Vaccine-associated rhabdomyosarcoma with spinal epidural invasion and pulmonary metastasis in a cat

A 7-year-old, female, domestic medium-haired cat had a recurrent deep dermal mass in the interscapular region after initial surgical removal 3 months earlier. The cat had received a killed rabies vaccine and a five-in-one vaccine in the same area about 2 months prior to the first surgery. The relapsed mass was diagnosed as vaccine-associated sarcoma. The cat was euthanized 2 months later because of hind limb paralysis. At necropsy, multiple, poorly demarcated, nodular masses were seen in the muscles around the shoulders, neck, and thoracic vertebrae. Pulmonary metastasis and spinal epidural invasion at T1-T3 with regional cord compression and malacia were observed. Microscopically, the masses consisted of interwoven bundles of spindle cells with prominent multinucleated giant cell formation. The neoplastic cells stained strongly positive for myoglobin, and moderately but variably positive for vimentin, desmin, and alpha- smooth muscle actin. Phosphotungstic acid-hematoxylin staining revealed cytoplasmic striations in scattered tumor cells. The tumor was considered a vaccine-associated rhabdomyosarcoma.

Ocular metastasis of a vaccine-associated fibrosarcoma in a cat

A 6-year-old, neutered male domestic shorthair cat was evaluated for a recurrent vaccine-associated fibrosarcoma. The cat had three excisions of the tumour prior to presentation and was referred for radiation therapy. Ten months following treatment with radiation therapy, the cat was presented again for a cloudy appearance to the eye. An exenteration was performed, and biopsy revealed fibrosarcoma. At the same time, two discrete pulmonary nodules were identified on thoracic radiographs. Two doses of doxorubicin (20 mg/m(2)) and cyclophosphamide (100 mg/m(2)) were administered intravenously 3 weeks apart. Despite treatment, the pulmonary nodule doubled in size. This case represents the first antemortem report of ocular metastasis of a vaccine-associated sarcoma and supports the highly aggressive nature of these tumours.

Facilitation of antibody forming responses to viral vaccine antigens in young cats by recombinant baculovirus-expressed feline IFN-gamma

We assessed the effect of recombinant feline IFN-gamma as vaccine adjuvant for in vivo antibody responses of young 3-month-old kittens to inactivated antigens of rabies and calicivirus, both natural pathogens for cats. When compared to responses following immunization with antigen alone co-administration of baculovirus-expressed cat IFN-gamma significantly enhanced serum antibody titers to both viral antigens; to levels comparable with responses evoked by commonly known saponin and alum adjuvants. Adjuvanticity by feline IFN-gamma was dose-dependent and all doses tested were well tolerated. We conclude that, when further optimized for in vivo delivery, feline IFN-gamma may represent a safe and efficient natural vaccine adjuvant for certain antigens in cats.

Immunization of dogs and cats with a DNA vaccine against rabies virus

The applicability of DNA immunization technology for vaccine development in companion animals was investigated by immunizing dogs and cats by the intramuscular (i.m.) and intradermal (i.d.) routes with a plasmid DNA vector encoding the rabies virus glycoprotein G. In dogs, administration of 100 microg DNA doses by the i.m. route resulted in stronger and more durable rabies virus neutralizing antibody (RVNA) titers than those obtained by i.d. inoculation. In contrast, i.m. vaccination of cats with a similar dose was less effective in terms of mean titer and seroconversion frequency. However, efficacy was improved by increasing the dosage to 300 microg of DNA per immunization. Interestingly, i.d. inoculation of cats appeared to be a superior route of delivery in this species, resulting in higher seroconversion frequency than i.m. administration. In addition, geometric mean RVNA titers in i.d. inoculated cats increased over four-fold during a seven month period following a second and final immunization. These results demonstrate that non-facilitated, naked DNA vaccines can elicit strong, antigen-specific immune responses in dogs and cats, and DNA immunization may be a useful tool for future development of novel vaccines for these species.