Feline injection site sarcoma: immunohistochemical characteristics

Expression of αv Integrin in Feline Injection-Site Sarcoma (FISS): Preliminary Investigations

Feline injection-site sarcomas (FISSs) are malignant skin tumors of mesenchymal origin arising at local post-vaccination (or injection) sites. In recent years, a fluorescence imaging technique based on probes targeting αvβ3 integrin has been effectively applied for the surgical complete resection of the tumor. In our study, we investigated the utility of a commercially available anti-αv integrin polyclonal antibody for the histopathological evaluation of FISS's surgical excision margins. We collected 10 formalin-fixed paraffin-embedded (FFPE) feline excisional biopsies with a histopathological diagnosis of FISS (7 fibrosarcomas and 3 pleomorphic sarcomas) and wide margin tissue, along with one subcutaneous injection-site granuloma and 6 osteosarcomas. Samples were processed for histology, and slides were stained for IHC with the anti-αv integrin antibody. Immunostained slides were evaluated for the cellular localization and intensity of the staining in different neoplastic and non-neoplastic cell populations. Neoplastic and non-neoplastic spindle cells had cytoplasmic positivity in all fibrosarcomas. Inflammatory cells, including macrophages of the injection-site granuloma, were negative. Multinucleated giant cells in the pleomorphic sarcomas had an intense membranous positivity. Although the anti-αv integrin antibody was ineffective for the histopathological evaluation of surgical excision margins, the membranous localization of αv integrin in multinucleated giant cells of pleomorphic sarcomas suggests that it plays a role in the oncogenesis of this FISS variant.

Unlocking immunotherapy targets: programmed death 1 and its ligand and their correlation with tumour grade in feline injection site sarcoma

In this study, the immunohistochemical expression of programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1), which could facilitate a novel approach to immunotherapy for feline injection site sarcomas (FISSs), was investigated. Treatment strategies based on the suppression of this pathway are possible for tumours expressing PD-1/PD-L1. In this context, FISSs were histologically classified, the grade of sarcoma and the intensity of lymphocyte infiltration determined and PD-1 and PD-L1 expression evaluated in tumours of different grade. Tumours were immunolabelled for vimentin, S100, smooth muscle actin and sarcomeric actin. Fibrosarcoma was diagnosed in eight cases, undifferentiated sarcoma in one case, liposarcoma in one case and rhabdomyosarcoma in one case. PD-1 expression was found mainly in lymphoid infiltrations and macrophage-like cells, while PD-L1 was found primarily in tumour cells and infiltrated macrophage-like cells. By Pearson correlation analysis, tumour differentiation was found to have a moderate correlation with PD-1 (P <0.05) and a high correlation with PD-L1 (P <0.01). Tumour grade had a low correlation with PD-1 and a moderate correlation with PD-L1 (P >0.05). A moderate correlation was also detected between PD-1 and PD-L1 (P <0.05). It was concluded that the increased expression of PD-1 and PD-L1 may be associated with poor tumour differentiation and, therefore, poor prognosis in FISS.

Expression of programmed cell death protein 1 and programmed cell death ligand 1 in feline injection site fibrosarcomas

Feline injection site fibrosarcomas represent a unique challenge in veterinary oncology due to their association with injection sites and aggressive behaviour. The study explores the expression of immune checkpoints programmed cell death protein 1 and programmed cell death ligand 1 in the malignancy, aiming to unravel their potential significance in tumour progression. The study included 31, archival diagnostic specimens of feline fibrosarcomas, located in the common injection sites. The programmed cell death protein 1 and programmed cell death ligand 1 expression in tumour cells and tumour infiltrating lymphocytes were assessed by immunohistochemical methods. Programmed cell death protein 1 and programmed cell death ligand 1 expression were observed in 84% and 81% of cases, respectively. In tumour infiltrating lymphocytes the PD-1 expression was observed in 71% of cases. Notably, higher programmed cell death protein 1 expression correlated with tumour grade and heightened inflammation score, suggesting a potential association with tumour aggressiveness. Similarly, programmed cell death ligand 1 expression exhibited a positive correlation with tumour grade and inflammation score. The observed findings suggest a potential role for programmed cell death protein 1 and programmed cell death ligand 1 in tumour progression and immune response within the tumour microenvironment. Moreover, this study contributes to a deeper understanding of feline injection site fibrosarcoma pathogenesis, emphasizing the importance of considering immunological perspectives in developing effective treatment strategies for this challenging condition. Further investigations are warranted to advance our knowledge and refine therapeutic approaches for feline injection site fibrosarcoma management.

Comparison of MMP-2, MMP-9, COX-2, and PGP Expression in Feline Injection-Site and Feline Noninjection-Site Sarcomas-Pilot Study

Feline injection-site sarcomas (FISSs) are aggressive neoplasms that have been associated mostly with vaccination. Feline noninjection-site sarcomas (non-FISSs) are less frequently observed in cats and may arise in any anatomic site. This study aimed to determine the differences in the expression of the selected proteins (matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), cyclooxygenase-2 (COX-2), and P-glycoprotein (PGP)) and their correlation with the mitotic count in FISS and non-FISS, in order to characterize their immunohistochemical features. A preliminary study of eleven samples of FISS and eight samples of non-FISS was performed using immunohistochemistry. Among all the tested sarcomas, 80.4% of the tumors were positive for COX-2, 90.2% were positive for MMP-9, and 100% were positive for PGP. The results showed that the expressions of COX-2, MMP-9, and PGP were significantly higher in FISS than in non-FISS (COX-2-p ≤ 0.001; MMP-9-p ≤ 0.05; and PGP-p ≤ 0.05). A Spearman rank correlation analysis showed a moderate negative correlation between the expression of COX-2 and MMP-9 in FISS (r = -0.52). A strong negative correlation between COX-2 and PGP (r = -0.81), a moderate positive correlation between MMP-2 and MMP-9 (r = +0.69), and a moderate negative correlation between MMP-2 and PGP (r = -0.44) were observed in non-FISS. In summary, our study presents the immunohistochemical profile of the proteins involved with inflammation and carcinogenesis in FISS and non-FISS, which can contribute to expanding the knowledge of tumor biology.

Periocular fibrosarcoma with lipogranulomatous conjunctivitis in a cat

A 9-year-old, female spayed domestic short-haired cat was presented with a 4-year history of bilateral lipogranulomatous conjunctivitis (LGC), which was confirmed via histopathology. Thirteen months following the initial biopsy, the cat was presented with a rapidly progressive mass lesion of the palpebral conjunctiva of the right eye. A surgical debulking, followed 1 month later by exenteration after marked regrowth of the mass confirmed fibrosarcoma. This case report is the first to describe a cat with chronic bilateral LGC that later developed a unilateral fibrosarcoma within the eyelid tissue of the right eye. Fibrosarcoma should be considered a differential in any cat with chronic LGC that develops a rapidly progressive mass in the eyelid.

Feline Facial Spindle Cell Tumors in 29 Cats: Histomorphological and Immunohistochemical Characterization

Soft tissue tumors/sarcomas (STSs) in felines, encompassing a variety of mesenchymal tumors with similar histomorphological features, present diagnostic challenges due to their diverse cellular origins and the overlap with other tumor types such as feline sarcoid. This study aimed to delineate the clinical, histomorphological, and immunohistochemical characteristics of 34 feline facial spindle cell tumors affecting 29 cats, including testing for bovine papillomavirus type 14 (BPV14), the virus causing feline sarcoids. Only five out of 12 tumors previously diagnosed as feline sarcoids based on histomorphology were confirmed by PCR for BPV14, underscoring the importance of comprehensive diagnostic approaches to accurately distinguish between STSs and feline sarcoids. This study shows that most facial spindle cell tumors were compatible with peripheral nerve sheath tumors (PNSTs) based on positive immunohistochemical staining for Sox10 and other immunohistochemical markers such as GFAP, NSE, and S100. Some of these tumors displayed as multiple independent masses on the face or as erosive and ulcerative lesions without obvious mass formation, an atypical presentation and an important highlight for general practitioners, dermatologists, and oncologists. This study also describes periadnexal whorling of neoplastic cells as a novel histomorphologic finding in feline facial PNSTs and emphasizes Sox10 as a useful complementary immunohistochemical marker for the diagnosis of facial PNST in cats, providing valuable insights for veterinary pathologists.

A Scoping Review on Tyrosine Kinase Inhibitors in Cats: Current Evidence and Future Directions

Tyrosine kinase inhibitors (TKIs) have become invaluable in the treatment of human and canine malignancies, but their role in feline oncology is less defined. While toceranib phosphate and masitinib mesylate are licensed for use in dogs, no TKI is yet approved for cats. This review systematically maps the research conducted on the expression of tyrosine kinases in neoplastic and non-neoplastic domestic feline tissues, as well as the in vitro/in vivo use of TKIs in domestic cats. We identify and discuss knowledge gaps and speculate on the further research and potential indications for TKI use in cats. A comprehensive search of three electronic databases and relevant paper reference lists identified 139 studies meeting the inclusion criteria. The most commonly identified tumors were mast cell tumors (MCTs), mammary and squamous cell carcinomas and injection-site sarcomas. Based on the current literature, toceranib phosphate appears to be the most efficacious TKI in cats, especially against MCTs. Exploring the clinical use of TKIs in mammary carcinomas holds promise. Despite the progress, currently, the evidence falls short, underscoring the need for further research to discover new indications in feline oncology and to bridge the knowledge gaps between human and feline medicine.

Feline Injection-Site Sarcoma and Other Adverse Reactions to Vaccination in Cats

Vaccine-associated adverse events (VAAEs), including feline injection-site sarcomas (FISSs), occur only rarely but can be severe. Understanding potential VAAEs is an important part of informed owner consent for vaccination. In this review, the European Advisory Board on Cat Diseases (ABCD), a scientifically independent board of feline medicine experts, presents the current knowledge on VAAEs in cats, summarizing the literature and filling the gaps where scientific studies are missing with expert opinion to assist veterinarians in adopting the best vaccination practice. VAAEs are caused by an aberrant innate or adaptive immune reaction, excessive local reactions at the inoculation site, an error in administration, or failure in the manufacturing process. FISS, the most severe VAAE, can develop after vaccinations or injection of other substances. Although the most widely accepted hypothesis is that chronic inflammation triggers malignant transformation, the pathogenesis of FISS is not yet fully understood. No injectable vaccine is risk-free, and therefore, vaccination should be performed as often as necessary, but as infrequently as possible. Vaccines should be brought to room temperature prior to administration and injected at sites in which FISS surgery would likely be curative; the interscapular region should be avoided. Post-vaccinal monitoring is essential.

Effects of selective cyclooxygenase-2 inhibitor robenacoxib on primary cells derived from feline injection-site sarcoma

Feline injection-site sarcomas (FISSs) are highly invasive malignant mesenchymal neoplasms that arise from injection sites in cats. Although the tumorigenesis of FISSs is still uncertain, there is a consensus that FISS is associated with chronic inflammation caused by irritation of injection-related trauma and foreign chemical substances. Chronic inflammation can provide a proper microenvironment for tumour development, which has been known as one of the risk factors of tumorigenesis in many tumours. To investigate the tumorigenesis of FISS and screen for its potential therapeutic targets, cyclooxygenase-2 (COX-2), an inflammation-enhancing enzyme, was selected as a target for this study. In vitro experiments using FISS- and normal tissue-derived primary cells and robenacoxib, a highly selective COX-2 inhibitor, were performed. The results demonstrated that expression of COX-2 could be detected in formalin-fixed and paraffin-embedded FISS tissues and FISS-derived primary cells. Cell viability, migration and colony formation of FISS-derived primary cells were inhibited, and cell apoptosis was enhanced by robenacoxib in a dose-dependent manner. However, susceptibility to robenacoxib varied in different lines of FISS primary cells and was not completely correlated with COX-2 expression. Our results suggest that COX-2 inhibitors could be potential adjuvant therapeutics against FISSs.

Molecular characterization of feline immune checkpoint molecules and establishment of PD-L1 immunohistochemistry for feline tumors

Spontaneous tumors are a major cause of death in cats. Treatment of human tumors has progressed dramatically in the past decade, partly due to the success of immunotherapies using immune checkpoint inhibitors, such as anti-programmed death 1 (PD-1) and anti-PD-ligand 1 (PD-L1) antibodies. However, little is known about the PD-1 pathway and its association with tumor disease in cats. This study investigated the applicability of anti-PD-1/PD-L1 therapy in feline tumors. We first determined the complete coding sequence of feline PD-L1 and PD-L2, and found that the deduced amino acid sequences of feline PD-L1/PD-L2 share high sequence identities (66-83%) with orthologs in other mammalian species. We prepared recombinant feline PD-1, PD-L1, and PD-L2 proteins and confirmed receptor-ligand binding between PD-1 and PD-L1/PD-L2 using flow cytometry. Next, we established an anti-feline PD-L1 monoclonal antibody (clone CL1Mab-7) to analyze the expression of PD-L1. Flow cytometry using CL1Mab-7 revealed the cell surface expression of PD-L1 in a feline macrophage (Fcwf-4) and five mammary adenocarcinoma cell lines (FKNp, FMCm, FYMp, FONp, and FONm), and showed that PD-L1 expression was upregulated by interferon-γ stimulation. Finally, immunohistochemistry using CL1Mab-7 also showed PD-L1 expression in feline squamous cell carcinoma (5/5, 100%), mammary adenocarcinoma (4/5, 80%), fibrosarcoma (5/5, 100%), and renal cell carcinoma (2/2, 100%) tissues. Our results strongly encourage further investigations of the PD-1/PD-L1 pathway as a potential therapeutic target for feline tumors.

Feline Soft Tissue Sarcomas: A Review of the Classification and Histological Grading, with Comparison to Human and Canine

Simple Summary

Soft tissue sarcomas are a common form of cancer arising in the skin and connective tissues of domestic cats. Soft tissue sarcomas encompass a group of different histological subtypes of tumours, which can behave in a range of different ways in the patient. In dogs and in humans, this group of tumours can be given a histological score (“grade”) at the time of diagnosis, which is prognostic, but there is no equivalent, well-established grading system for these tumours in cats. This review looks at soft tissue sarcomas in terms of which histological subtypes of tumour should be included in this group, and how pathologists approach their grading, comparing feline tumours with their human and canine counterparts.

Abstract

Soft tissue sarcomas are one of the most commonly diagnosed tumours arising in the skin and subcutis of our domestic cats, and are malignant neoplasms with a range of histological presentations and potential biological behaviours. However, unlike their canine and human counterparts, there is no well-established histological grading system for pathologists to apply to these tumours, in order to provide a more accurate and refined prognosis. The situation is further complicated by the presence of feline injection site sarcomas as an entity, as well as confusion over terminology for this group of tumours and which histological types should be included. There is also an absence of large scale studies. This review looks at these tumours in domestic cats, their classification and histological grading, with comparisons to the human and canine grading system.

Non-injection-site soft tissue sarcoma in cats: outcome following adjuvant radiotherapy

OBJECTIVES

Biological behaviour and treatment options of non-injection-site soft tissue sarcomas (nFISS) in cats are less well understood than in dogs. The aim of this retrospective study was to assess the outcomes of cats with nFISS following treatment with adjuvant radiotherapy.

METHODS

The medical records of cats with soft tissue sarcomas in locations not associated with, and histology reports not suggestive of, injection-site sarcomas were reviewed. All cats underwent adjuvant radiotherapy, either hypofractionated (32-36 Gy delivered in weekly 8-9 Gy fractions) or conventionally fractionated (48-54 Gy delivered in 16-18 3 Gy fractions) to microscopic disease.

RESULTS

In total, 18 cats were included in the study, 17 with extremity nFISS and one with facial nFISS. Nine received radiotherapy after a single surgery and nine after multiple surgeries for recurrent nFISS. Eight cats were treated with a hypofractionated protocol and 10 with a conventionally fractionated protocol. The median follow-up time was 540 days (range 51-3317 days). The tumour recurred in eight (44.4%) cats following adjuvant radiotherapy; it recurred in three (37.5%) cats following a hypofractionated protocol and in five (50%) cats following a conventionally fractionated protocol. The overall median progression-free interval (PFI) for 17/18 cats was 2748 days, while the median PFI for the 7/8 cats with recurrence was 164 days. The recurrence for one cat was reported, but the date was unknown and it was therefore censored from these data. When stratifying based on the protocol, the median PFI for hypofractionated and conventionally fractionated protocols was 164 days and 2748 days, respectively. Statistically, there was no significant difference between the two protocols (P = 0.636).

CONCLUSIONS AND RELEVANCE

Adjuvant radiotherapy resulted in good long-term tumour control in 12/18 cats with nFISS. Further studies in larger populations are required to assess the significance of radiation dose and fractionation on tumour control and the effect of multiple surgeries prior to initiation of radiotherapy on outcome.

Investigating the role of signal transducer and activator of transcription 3 in feline injection site sarcoma

BACKGROUND

Feline injection-site sarcomas (FISSs) are malignant mesenchymal tumors of different histotypes. The pathogenesis of FISS has been correlated with chronic inflammation, resulting in neoplastic transformation. Activation of the Janus kinase-signal transducer and activator of transcription 3 (STAT3) have been demonstrated to play a critical role in tumor development by regulating signaling pathways involved in cell proliferation, survival, metastasis, and angiogenesis in human medicine. To characterize the role of STAT3 in FISS, we first detected STAT3 and phosphorylated STAT3 in formalin-fixed and paraffin-embedded (FFPE) FISS tissues using immunohistochemical staining.

RESULTS

STAT3 was detected in 88.9% (40/45) of FISS cases, and phosphorylated STAT3 was detected in 53.3% (24/45) of cases. However, the expression levels of both forms of STAT3 were not correlated with tumor grade. To study the role of STAT3 in tumor survival, two primary cells derived from FISSs of two cats exhibiting consistent immunophenotypes with their parental FFPE tissues were established. A dose-dependent inhibitory effect on cell proliferation was observed in both primary FISS cells treated with the STAT3 inhibitor, 5-hydroxy-9,10-dioxo-9,10-dihydroanthracene-1-sulfonamide.

CONCLUSIONS

The STAT 3 may play an important role in the tumorigenesis of FISS and be a potential molecular therapeutic target for FISS.

Hormone receptor expression, clinical and histopathological analysis in feline injection site sarcomas

Feline injection site sarcomas (FISS) are aggressive, with high recurrence and rarely metastasising. The objective of this study was to evaluate, by immunohistochemistry, the expression of oestrogen (ER) and progesterone (PR) receptors in FISS and correlate them with clinical and histopathological aspects. This was a retrospective study with 51 cases of FISS. Immunohistochemistry was performed to detect vimentin, ER, PR and Ki67 expression. Clinical, histopathological and immunohistochemical characteristics were predictor variables and the expression of ER and PR were the dependent ones. Twenty-eight (55%) of the 51 FISS cases were female and 23 (45%) male with 10.7 ± 4.2 years and median tumour size of 3 cm (2.0-5.4). The trunk was the most affected site, with 38 cases (84%). Histological grade III was observed in 57% of the cases, considering differentiation score, necrosis and mitotic index. ER expression, positive in 64% of cases, was associated with the mitotic index (P = .05) and degree of pleomorphism (P = .04). PR was not associated with the variables and 63% of cases were negative for this receptor. Thus, ER expression can affect tumour growth. The knowledge on the FISS hormonal expression is important to clarify the pathophysiological mechanisms. Further studies are needed to predict the value of ER expression in the prognosis of FISS.

Cyclooxygenase-2 as a Biomarker with Diagnostic, Therapeutic, Prognostic, and Predictive Relevance in Small Animal Oncology

In canine and feline populations, the number of neoplasm cases continues to increase around the world. Attempts are being made in centres of research to identify new biomarkers that speed up and improve the quality of oncological diagnostics and therapy in human and animal tumour patients. Cyclooxygenase-2 (COX-2) is a promising biomarker with increasing relevance to human oncology, but as yet with less application in veterinary oncology. The expression of COX-2 increases significantly during pathological processes involving inflammation, pain or fever. It is also overexpressed in humans presenting various types of tumours and in selected types of tumours in animals, particularly in dogs. This article discusses the expression of COX-2 in canine and feline tumours, the importance of COX-2 as a biomarker with diagnostic, therapeutic, prognostic and predictive relevance in oncology, and the clinical significance of inhibiting COX-2 overexpression in tumours.