A review of histiocytic diseases of dogs and cats

Identification of immune suppressor candidates utilizing comparative transcriptional profiling in histiocytic sarcoma

Histiocytic sarcoma (HS) is a rare yet lethal malignancy with no established standard of care therapies. A lack of pre-clinical models limits our understanding of HS pathogenesis and identification of therapeutic targets. Canine HS shares multiple clinical and genetic similarities with human HS, supporting its use as a unique translational model. Prior studies have investigated the immunogenicity of HS. Although increased tumor infiltrating lymphocyte (TIL) density is associated with favorable outcomes in canine HS, virtually all canine patients eventually succumb to progressive disease consistent with ultimate failure of anti-tumor immunity. To investigate potential regulators of the immune tumor microenvironment (TME), we undertook a comparative transcriptional approach of three long-lived cases of canine pulmonary HS with heavy T cell infiltrate and three short-lived cases of splenic HS that lacked significant T cell inflammation and compared these data to corresponding grossly normal tissues from dogs undergoing necropsy. This comparison identified PDCD1, encoding the immune checkpoint PD-1, and SPP1, encoding the secreted pro-tumorigenic protein osteopontin, as positive differentially expressed genes (DEGs) in canine HS. TXNIP, encoding the tumor suppressor TXNIP, was the most significant negative DEG. Comparative transcriptomic studies revealed conservation of enriched (including SPP1) and depleted (including TXNIP) DEGs between canine and human HS patients. Immunohistochemistry demonstrated osteopontin in the TMEs of canine and human HS. Collectively, we uncover PD-1, osteopontin, and TXNIP as putative actionable targets in HS and further establish canine HS as a preclinical platform to screen novel immunotherapeutic approaches for this deadly disease.

Sarcomas of synovial origin in dogs: An updated review

The purpose of this review is to clarify the terminology, possible cells of origin, and expected behavior of the most common synovial tumors in dogs. The synovial lining consists of 2 cell types, type A and type B. Type A synoviocytes are histiocytes of bone marrow origin that are immunoreactive with antibodies against typical markers of histiocyte origin, such as CD18, Iba-1, and CD204. Certain breeds and dogs with previous injury to a joint, especially cranial cruciate ligament rupture, are predisposed to synovial histiocytic sarcoma. Type B synoviocytes are mesenchymal cells that produce synovial fluid. There are no specific markers of type B synoviocytes, but based on their gross and microscopic appearance, synovial myxosarcomas (previously considered synovial myxomas) are presumed to be of type B synoviocyte origin. These can infiltrate into surrounding tissues, but are slow-growing and rarely metastasize, and then only to regional lymph nodes. Synovial histiocytic sarcomas and myxosarcomas can cause lysis in multiple bones surrounding the joint, but they have different prognoses and require histopathology and sometimes immunohistochemistry to diagnose them. Synovial sarcoma and synovial cell sarcoma are terms used in the human medical literature for a tumor that is not of synovial origin; these terms should not be used in veterinary medicine.

MRI Characteristics of Primary Brain Tumors and Advanced Diagnostic Imaging Techniques

Extensive descriptions of MRI characteristics of canine and feline brain tumors allow for relatively accurate lesion detection, discrimination, and presumptive diagnosis on MRI. Ambiguous and overlapping MRI features between brain lesion and tumor as well as tumor types is a limitation that necessitates histopathology for final diagnosis, which is often not available antemortem. Non-invasive advanced diagnostic imaging techniques continue to be developed to enhance sensitivity and specificity for brain tumor diagnosis on MRI in dogs and cats.

Novel Insights Into the Ultrastructural and Immunofluorescence Characteristics of Limb Skin in the Red-Eared Slider Turtle (Trachemys scripta elegans)

The red-eared slider turtle, a species facing environmental challenges and habitat loss, exhibits a complex skin architecture that is crucial for its adaptation and survival. Our study aims to provide a comprehensive characterization of the turtle's skin structure and to elucidate the distribution and localization of its various cellular components, with a focus on understanding the skin's role in adaptation and ecological interactions. To achieve these goals, we employed light microscopy, transmission electron microscopy (TEM), and comprehensive immunofluorescence using 10 specific antibodies. The forelimb skin displays large- and moderate-sized scales with variations in color, including dark, yellow, and gray hues, likely contributing to camouflage and protection. The skin consists of corneous material, the epidermis, the dermis, and the hypodermis. The stratum basalis, stratum spinosum, and peri-corneous layer constitute the three distinct layers of the epidermis. There are four distinct types of chromatophores, including melanocytes located in the epidermis, while melanophores, xanthophores, and iridophores are found within the dermal layer. The skin also exhibits well-developed peripheral nerves, blood vessels, and subcutaneous muscles. Immunofluorescence staining further elucidates the distribution and localization of various skin cells. E-cadherin and CK14 are strongly expressed in the epidermal layers, excluding the corneous material. E-cadherin surrounds keratinocyte cells in the epidermis, facilitating cell-cell adhesion, while CK14 is present inside the keratinocyte cells, contributing to their internal structural integrity. Sox10 and CD117 identify the four chromatophore types, with Melan-A specifically detecting only melanocytes and melanophores and not labeling xanthophores and iridophores. Tom20 is used to detect mitochondrial distribution and intensity in the skin, revealing a high density of mitochondria in all epidermal layers, especially in melanocytes and melanophores, compared to xanthophores and iridophores. Numerous telocytes, spindle-shaped with extensions called telopods, are detected in the dermis using CD34, PDGFRα, and vimentin. The skin of the red-eared slider also shows abundant myofibroblasts and well-developed vascularization, with numerous blood vessels detected using α-SMA. This novel study offers an in-depth examination of the limb skin of the red-eared slider through the use of 10 distinct antibodies, uncovering the intricate interactions among its cellular components and providing valuable insights into its anatomical structure and physiological adaptations. Our findings contribute to a better understanding of the turtle's skin, which may aid in its conservation and management.

Antitumor effects of inhibitors of ERK and Akt pathways in canine histiocytic sarcoma cell lines

Canine histiocytic sarcoma (CHS) is characterized by aggressive biological behavior. In our previous study, ERK and Akt pathways were found to be activated in CHS tissues. Thus, the objective of this study was set to investigate the relationships between the activation status of these pathways and the proliferation of CHS cell lines by examining the effects of single and co-administrations of drugs targeting these pathways. First, we evaluated the changes in cell proliferations and the activations of ERK and Akt pathways after treatments with ERK and Akt-specific inhibitors in CHS cells. Then, these changes after treatments with dasatinib and trametinib were also examined in CHS cells. Inhibitors specific to ERK and Akt pathways successfully inhibited the respective pathways in CHS cell lines. It was also indicated that these pathways were associated with the regulations of proliferations of CHS cells, although the anti-proliferative effect was not necessarily observed by inhibition of Akt pathway alone. Dasatinib and trametinib also showed the inhibitions of Akt and ERK pathway activations, respectively, in CHS cells. However, the anti-proliferative effects of these drugs varied among CHS cell lines, and co-administration showed enhanced anti-proliferative effects in only a part of CHS cell lines. Further studies are needed to investigate the molecular mechanisms associated with the sensitivities to these molecular-targeted drugs in CHS cells.

Sterile granulomatous panuveitis in dogs in the United Kingdom: A review of 33 cases

PURPOSE

To describe the clinical and histopathological features of a sterile granulomatous panuveitis syndrome in 33 dogs that underwent enucleation and ocular histopathology.

METHODS

Retrospective review of the medical records and ocular histopathology reports of 33 cases. Inclusion criteria were enucleation in conjunction with characteristic clinical and histopathological features.

RESULTS

Thirteen breeds were represented (including crossbreeds). Panuveitis was acute and fulminating, and secondary glaucoma was common (n = 27). Interval from initial presentation to enucleation was 99 days (median 33 days, range 5-605 days). The mean age at enucleation was 6.7 years. Ocular signs were initially unilateral (n = 18) or bilateral (n = 15). The disease became bilateral in 18/25 cases that initially underwent unilateral enucleation, resulting in enucleation or euthanasia in 9/18 (mean interval of 168 days). Seven out of 59 eyes had a good outcome following topical anti-inflammatory and systemic immunosuppressive therapy. None of the dogs had travel history nor relevant systemic signs from presentation to follow-up (mean 619 days, range 16-3012 days). Histopathology revealed histiocytic and lymphoplasmacytic panuveitis with pigment dispersion, and no infectious agents were identified on light microscopy.

CONCLUSION

To the authors' knowledge, this is the first report of a sterile granulomatous panuveitis syndrome in dogs in the UK. The clinical signs are severe, with rapid progression, and can result in bilateral enucleation or euthanasia in affected dogs. There does not appear to be an age or breed predisposition, however further research is necessary in this regard. Early and aggressive intervention, with both topical and systemic immunosuppressive therapy, is recommended to reduce the risk of blindness, enucleation, and euthanasia.

Canine Histiocytic and Hemophagocytic Histiocytic Sarcomas Display KRAS and Extensive PTPN11/SHP2 Mutations and Respond In Vitro to MEK Inhibition by Cobimetinib

Histiocytic sarcoma (HS) is a rare and highly aggressive cancer in humans and dogs. In dogs, it has a high prevalence in certain breeds, such as Bernese mountain dogs (BMDs) and flat-coated retrievers. Hemophagocytic histiocytic sarcoma (HHS) is a unique form of HS that presents with erythrophagocytosis. Due to its rareness, the study of HHS is very limited, and mutations in canine HHS patients have not been studied to date. In previous work, our research group identified two major PTPN11/SHP2 driver mutations, E76K and G503V, in HS in dogs. Here, we report additional mutations located in exon 3 of PTPN11/SHP2 in both HS and HHS cases, further supporting that this area is a mutational hotspot in dogs and that mutations in tumors and liquid biopsies should be evaluated utilizing comprehensive methods such as Sanger and NextGen sequencing. The overall prevalence of PTPN11/SHP2 mutations was 55.8% in HS and 46.2% in HHS. In addition, we identified mutations in KRAS, in about 3% of HS and 4% of HHS cases. These findings point to the shared molecular pathology of activation of the MAPK pathway in HS and HHS cases. We evaluated the efficacy of the highly specific MEK inhibitor, cobimetinib, in canine HS and HHS cell lines. We found that the IC50 values ranged from 74 to 372 nM, which are within the achievable and tolerable ranges for cobimetinib. This finding positions cobimetinib as a promising potential candidate for future canine clinical trials and enhances our understanding of the molecular defects in these challenging cancers.

Establishment of a histiocytic sarcoma cell line and anti-tumor effect of bortezomib in the African pygmy hedgehog (Atelerix albiventris)

The African pygmy hedgehog (Atelerix albiventris) is known to have a high incidence of tumor. However, investigating the tumors of this species has been constrained by the limited availability of research materials such as cell lines and genome information. In this study, we successfully established a novel cell line from a histiocytic sarcoma (HS) of an African pygmy hedgehog, allowing us to conduct a drug screening. We investigated using FDA-approved drug library screening to determine which anticancer drug this tumor cell line is sensitive to, and as a result of apoptosis experiments, bortezomib among the three proteasome inhibitors was found to induce cell death of cancer cells by significantly increasing caspase-3 cleavage (P<0.01). Thus, we elucidated that the proteasome inhibitors, particularly bortezomib, exhibit anti-tumor effects on a cell line derived from an HS in an African pygmy hedgehog through a mechanism comparable to that described in human tumors. This study reports the first characterized cell line from the African pygmy hedgehog and also highlights the potential utility of bortezomib as an anti-tumor treatment for HS in this species.

Persistence of Infectious Canine Distemper Virus in Murine Xenotransplants of Canine Histiocytic Sarcoma Cells after Intratumoral Application

Oncolytic viruses and morbilliviruses in particular, represent an interesting therapeutic approach for tumors with a poor prognosis and frequent resistance to conventional therapies. Canine histiocytic sarcomas (HS) exemplify such a neoplasm in need for new curative approaches. Previous investigations demonstrated a limited success of an acute intratumoral application of canine distemper virus (CDV) on xenotransplanted canine histiocytic sarcoma cells (DH82 cells), while persistently CDV-infected DH82 cell transplants exhibited a complete spontaneous regression. Therefore, the present study focuses on an intratumoral application of persistently CDV vaccine strain Onderstepoort-infected DH82 (DH82 Ond p.i.) cells into non-infected subcutaneous DH82 cell transplants in a murine model. DH82 cell transplants that received 10 applications, two days apart, showed a transient growth retardation as well as larger areas of intratumoral necrosis, lower mitotic rates, and a decreased intratumoral vascularization compared to controls. Viral mRNA was detected in all neoplasms following application of DH82 Ond p.i. cells until 66 days after the last injection. Furthermore, infectious virus was present until 62 days after the last injection. Although complete regression was not achieved, the present application regimen provides promising results as a basis for further treatments, particularly with genetically modified viruses, to enhance the observed effects.

Histopathological and Ultrastructural Study of a Canine Langerhans Cell Tumour (Canine Cutaneous Histiocytoma)

Canine cutaneous histiocytoma (CCH) represents a significant proportion of dog skin tumours, often manifesting as the most common neoplastic skin condition in young animals. Predominantly affecting dogs under four, these tumours appear primarily as solitary lesions that may regress spontaneously. This study, conducted over five years at the University of Trás-os-Montes e Alto Douro, involved a detailed histopathological and ultrastructural examination of 93 CCH cases. Histologically, these tumours showed distinct patterns of lymphoid infiltration, which contributed to their classification into four groups based on the inflammatory response and histological architecture. Most tumours displayed signs of epidermal invasion and frequent mitotic figures, with necrosis present in over half of the cases. Ultrastructurally, the neoplastic cells were characterised by pleomorphism, abundant organelles, and adherens-type junctions. This study offers significant insights into the pathophysiology and morphological characteristics of CCH, underscoring the importance of detailed histological and ultrastructural analysis in accurately diagnosing and understanding this common canine tumour.

MRI of a presumptive intracranial histiocytic sarcoma with extracranial extension in a cat

Case summary

A 4-year-old female neutered Scottish Fold shorthair cat was presented for further investigation of circling towards the right. MRI of the brain revealed an extensive, right-sided temporal muscle lesion with associated frontotemporal bone osteolysis, intracranial, extra-axial extension along the calvarial convexity with severe pachy- and leptomeningeal thickening and contrast enhancement, and an intra-axial space-occupying lesion in the right piriform lobe. The regional lymph nodes were moderately enlarged. Cytology of the right parotid lymph node and the temporal muscle was performed and histiocytic sarcoma (HS) was diagnosed. The owners elected euthanasia.

Relevance and novel information

HS of the central nervous system (CNS) is a very rare neoplastic condition in cats. Although a few case reports mention MRI, to our knowledge, the characterisation of MRI features of feline CNS HS have not been investigated in detail. Therefore, the aim of this case report was to describe the MRI characteristics in a feline HS involving not only the CNS, but also the fronto-temporal bone, temporal muscle and the regional lymph nodes. In particular, aggressive neoplastic bone invasion was a novel finding.

Immune checkpoint regulation is critically involved in canine cutaneous histiocytoma regression

Introduction

Canine cutaneous histiocytoma (CCH) is a benign tumor frequently occurring in young dogs which is derived from Langerhans cells (LC). Distinguishing features of this tumor are its spontaneous regression following a rapid tumor growth. Impaired control of immune checkpoints during tumor development and progression is a widespread phenomenon which may result in an absent or ineffective immune response. The interaction between the inflammatory response and the expression of immune checkpoint molecules is only partially described in this tumor type. The aim of this study was to identify immune checkpoint molecules and molecules from the interferon-mediated immune response that are involved in the regression of CCH.

Methods

Forty-eight CCH derived from dogs ≤ 4 years of age were assigned to one of four groups according to the severity and distribution of lymphocyte infiltration. Using immunohistochemistry and whole-slide image scans of consecutive sections the expression of programmed death protein ligand 1 (PD-L1), CD80, CD86, Survivin, forkhead box protein 3, Ki-67, cleaved caspase-3, CD3, and mx1 were investigated. RNA in-situ hybridization was performed for transcripts of mx1 and interferon-γ.

Results

Neoplastic cells showed an expression of PD-L1, CD80, CD86, and Survivin. The density of CD80 expressing cells was negatively correlated with regression while the density of cleaved caspase-3 positive cells increased with regression. Mx1 transcripts and protein were predominantly localized in neoplastic cells while interferon-γ transcripts were most frequently detected in T-cells.

Conclusion

The expression of the immune checkpoint molecules CD86 and PD-L1 and particularly the reduced expression of CD80 in groups 3 and 4 indicate an influence of the investigated immune checkpoints on tumor regression. In parallel an activation of the apoptotic cascade during regression is suggested. Finally, the detection of mx1 within the neoplasm pinpoints to a yet undisclosed role of anti-cellular signaling in tumor immunity.

Disseminated histiocytic sarcoma in a degu (Octodon degus)

A 7-year-and-8-month-old, male degu (Octodon degus) with anorexia, depression, and labored breathing was found to have a thoracic effusion and enlargement of the right testis on radiographic examination. Despite treatment, the animal died. At necropsy, hepatomegaly, splenomegaly, and multifocal nodules on the intestinal serosa and mesentery were observed. Histologically, the foci were densely cellular invasive neoplasms composed of sheets of round to polygonal cells, with occasional multinucleated giant cells. Immunohistochemically, the neoplastic cells were immunopositive for ionized calcium-binding adapter molecule 1, human leukocyte antigen-DR, and CD204. These findings were consistent with disseminated histiocytic sarcoma.

Cutaneous Histiocytosis in an Eastern Gray Squirrel (Sciurus carolinensis)

A free-ranging Eastern gray squirrel (Sciurus carolinensis) was presented for ulcerated cutaneous masses at the base of both pinnae in July 2021. Diagnosis of cutaneous histiocytosis was achieved by histologic and immunohistochemical examination of one excised mass and supported by spontaneous resolution of the contralateral mass before the squirrel's release.

Pulmonary Langerhans Cell Histiocytosis in an African Lion: A Rare Case Report

BACKGROUND

Feline pulmonary Langerhans cells histiocytosis (PLCH) is a rare disorder that results in progressive respiratory failure secondary to pulmonary parenchymal infiltration with Langerhans cells (LCs). A diagnosis of PLCH is proposed based on the clinical features and pathological findings and confirmed based on the infiltrating histiocytic cells. There are few documented cases of feline PLCH, and this case report of PLCH in an African Lion could present new information and aspects of this feline histiocytic disease.

CASE PRESENTATION

An African lion at Hohhot Zoo showing severe hyporexia and dyspnea with subsequent mental depression and emaciation died of exhaustion after a 35-day course of illness. Empirical treatment did not have a significant effect. An autopsy revealed that the lungs were enlarged and hardened due to infiltrative lesions, with many yellowish-white foci in all the lobes and sections. Furthermore, the kidneys were atrophied and had scattered grayish-white lesions on the surface. At the same time, congestion was widely distributed in various locations, including the liver, subcutaneous loose connective tissues, serosal surface and other tissues and organs. Histologically, proliferative histiocytic cells (PHCs) were scattered in the alveolar cavities, bronchioles and submucosa of bronchioles, with evident cellular and nuclear pleomorphism, and thus the alveolar septa were obliterated. The histopathological changes in other organs included chronic sclerosing glomerulonephritis, proliferated Kupffer cells in the liver, adrenal edema and interstitial connective tissue hyperplasia, as well as atrophy of the small intestines and spleen. Furthermore, immunohistochemical analysis results were strongly positive for CD1a, vimentin, S100 and E-cadherin in the membrane or cytoplasm of PHCs, supporting an LC phenotype.

CONCLUSIONS

Here, we present a rare pulmonary Langerhans cell histiocytosis case in an African lion.

Atypical disseminated histiocytic sarcoma in a 7-month-old dog

A 7-month-old intact female bearded collie dog was admitted after a 2-week history of progressive cough, inappetence, and lethargy, with no response to previous treatment with doxycycline and steroids. Mild attenuation of lung sounds in the right middle hemithorax was the only abnormality detected on physical examination. Abdominal ultrasound and thoracic radiographs were performed and revealed multifocally distributed nodules and masses, well-circumscribed and of variable size in the kidneys and pulmonary parenchyma. Ultrasound-guided fine needle aspirates of the renal and pulmonary masses were taken. A cytologic evaluation of these lesions pointed towards a malignant mesenchymal neoplasia. Euthanasia was elected due to the poor prognosis and rapid progression. The post-mortem histopathology, a positive result to IBA1 immunoperoxidase staining, and a lack of detection of infectious agents, and negative E-cadherin immunostaining enabled the final diagnosis of a disseminated histiocytic sarcoma. We report an atypical form, both in breed and age, of canine disseminated histiocytic sarcoma. While all breeds can be affected, there is a clear predisposition in some, and no cases have been previously described in bearded collies. Moreover, to the authors' knowledge, this is the youngest dog with this histiocytic disorder described to date. Disseminated histiocytic sarcoma should be considered as a differential diagnosis of multinodular tumors in dogs, regardless of the anatomic location and age of the dogs, even in puppies.

First description of a primary esophageal histiocytic sarcoma in a dog

An 11-year-old male Schnauzer dog was referred for investigation of cough and regurgitation of one month duration and gradual hyporexia for the previous five months. Complete blood count showed severe leukocytosis. On ventrodorsal and lateral thoracic radiographs a soft tissue mass was visible in the craniodorsal mediastinum. Endoscopy showed esophageal dilatation and an irregular, nodular, friable, exophytic mass in the thoracic esophagus, which was invasive, vascularized and had ulcerated areas. The mass occluded approximately 90% of the esophageal lumen. The mucosa in the orad portion of the thoracic esophagus was pale and the aborad portion was hyperemic (red) with hemorrhages. The mucosa of the cervical and abdominal esophagus was macroscopically unremarkeble. Multiple biopsies using endoscopic cup biopsy forceps were taken from the mass for histopathologic analysis and a percutaneous endoscopic gastrostomy was performed. Histopathologic analysis of the biopsy samples was inconclusive due to the marked necrosis. The poor clinical condition of the dog precluded a more invasive approach, and palliative and supportive treatment was continued. After 100 days of follow-up, clinical signs worsened, and that day the dog had a fatal cardiac arrest due to aspiration pneumonia and sepsis. Postmortem examination showed a multilobulated mass in the esophageal wall with infiltration into the overlying esophageal mucosa and pulmonary and renal metastases. Histological examination revealed a poorly differentiated sarcoma. On immunohistochemical examination, the neoplastic cells showed marked cytoplasmic staining for vimentin and Iba-1. The proliferative rate was approximately 30% by Ki-67. Histological and immunohistochemical examination revealed the esophageal mass to be a primary histiocytic sarcoma. Histiocytic sarcoma is an extremely rare primary esophageal neoplasm in humans, and so far, there is no description in dogs. To the best of the authors knowledge this is the first case of primary esophageal histiocytic sarcoma in dogs. The clinical information reported here should improve recognition and aid in diagnosis of future cases.

Parthenolide As a Therapeutic for Disseminated Canine Neoplasms

This study provides a unique translational research opportunity to help both humans and dogs diagnosed with diseases that carry dismal prognoses in both species: histiocytic sarcoma (HS), hemangiosarcoma (HSA), and disseminated mastocytosis/mast cell tumor (MCT). Although exceedingly rare in humans, these so called "orphan diseases" are relatively more common in dogs. For these and other more commonplace cancers like lymphoma (Lym), dogs are an excellent translational model for human disease due to remarkably similar disease biology. In this study, assays were performed to assess the therapeutic potential of parthenolide (PTL), a known canonical nuclear factor kappa B (NF-κB) signaling inhibitor with additional mechanisms of antineoplastic activity, including alteration of cellular reduction-oxidation balance. Canine cell lines and primary cells are sensitive to PTL and undergo dose-dependent apoptosis after exposure to drug. PTL exposure also leads to glutathione depletion, reactive oxygen species generation, and NF-κB inhibition in canine cells. Standard-of-care therapeutics broadly synergize with PTL. In two canine HS cell lines, expression of NF-κB pathway signaling partners is downregulated with PTL therapy. Preliminary data suggest that PTL inhibits NF-κB activity of cells and extends survival time in a mouse model of disseminated canine HS. These data support further investigation of compounds that can antagonize canonical NF-κB pathway signaling in these cancers and pave the way for clinical trials of PTL in affected dogs. As dogs are an excellent natural disease model for these cancers, these data will ultimately improve our understanding of their human disease counterparts and hopefully improve care for both species. SIGNIFICANCE STATEMENT: Disseminated neoplasms in human and canine cancers are challenging to treat, and novel therapeutic approaches are needed to improve outcomes. Parthenolide is a promising treatment for histiocytic sarcoma, hemangiosarcoma, and mast cell neoplasia.

Immunohistochemical evidence of NF-kB activation in canine lymphomas, histiocytic sarcomas, hemangiosarcomas, and mast cell tumors

Increased or constitutive activation of nuclear factor kappa B (NF-kB) is a feature of many chronic disease processes, including cancer. While NF-kB overactivation has been documented extensively in human oncology, there is a relative paucity of data documenting the same phenomenon in veterinary medicine. To assess NF-kB activity, antibodies to p65 and p100/p52, which are components of NF-kB heterodimers, were first validated for specificity and canine cross-reactivity via Western blot and labeling of immortalized cell pellets. Then, nuclear labeling for these antibodies was assessed via QuPath software in over 200 tumor tissue samples (10 hemangiosarcomas, 94 histiocytic sarcomas, 71 lymphomas, and 28 mast cell tumors) and compared to immunolabeling in appropriate normal tissue counterparts. Greater than 70% of spontaneous canine tumors evaluated in this study had more nuclear p65 and p100/p52 immunoreactivity than was observed in comparable normal cell populations. Specifically, 144/204 (70.58%) of tumors evaluated had positive p65 nuclear labeling and 179/195 (91.79%) had positive p100/p52 nuclear labeling. Surprisingly, greater nuclear p100/p52 reactivity was associated with a longer progression-free survival (PFS) and overall survival (OS) in canine lymphomas. These results provide support and preliminary data to investigate the role of NF-kB signaling in different types of canine cancer.

MUM1/IRF4 immunolabeling of neoplastic Langerhans histiocytes in a putative case of canine Langerhans cell histiocytosis

Langerhans cell histiocytosis is a systemic histiocytic proliferative disease with cutaneous manifestations which is well described in human medical literature and has relatively recently been reclassified as a neoplastic disorder. The diagnosis of canine Langerhans cell histiocytosis has been proposed in the veterinary literature to refer to a histiocytic proliferative disease in the dog with clinical and histopathologic features that mirror the human disease. However, reports that invoke this diagnosis are rare and often lack complete diagnostic characterization. This case report presents an extensive diagnostic investigation of a putative case of Langerhans cell histiocytosis in a 3-year-old male castrated Golden Retriever dog, including gross, cytologic, histopathologic, and immunohistochemical findings. Furthermore, we document that canine LCH may have positive immunolabeling for the transcription factor multiple myeloma oncogene 1/interferon regulatory factor 4 (MUM1/IRF4), which is classically used for the diagnosis of canine plasma cell neoplasms.

Antemortem cytologic diagnosis of pulmonary Langerhans cell histiocytosis in a cat

Feline pulmonary Langerhans cell histiocytosis (FPLCH) is a rare histiocytic proliferative disease of middle-aged to older domestic cats. Langerhans cells in the terminal airways proliferate and infiltrate the interstitium and the airways to a lesser degree, widely effacing normal parenchyma. Historically, definitive diagnosis has required postmortem evaluation where pulmonary lesions have a classic gross and histologic morphology. Here, we present the first documented antemortem diagnosis of FPLCH using bronchoalveolar lavage (BAL) cytology and immunocytochemistry (ICC) in a 9-year-old British shorthair mix. The cat had a 3-month history of respiratory difficulty that was refractory to steroids and antimicrobials. Pulmonary radiographs had marked diffuse changes with a complex bronchointerstitial and micronodular pattern. BAL cytology revealed neutrophilic inflammation and markedly increased histiocytes with morphology distinct from typical pulmonary macrophages. ICC characterized histiocytes as CD1a+ /E-cadherin+ /CD11b- /PanCK- , consistent with a Langerhans cell phenotype. The cat was humanely euthanized due to poor prognosis and presented for necropsy. Gross, histopathologic, immunophenotypic, and ultrastructural findings confirmed a diagnosis of FPLCH. Proliferative cells were E-cadherin+ /Iba-1+ /CD18+ /CD1a+ /CD5+ /MHCII+ /CD204- /CD4- ; transmission electron microscopy identified the presence of Birbeck granules in the proliferating histiocytes, consistent with previous reports of FPLCH.

Undifferentiated pleomorphic sarcoma in a white-eared opossum (Didelphisalbiventris)

We report a case of high-grade undifferentiated pleomorphic sarcoma in a free-living white-eared opossum (Didelphis albiventris) in Central Brazil. Grossly, it appeared as a soft yellow mass, approximately 8 cm in diameter, with an irregular, adherent and ulcerated surface, which extended from the proximal epiphysis of the femur to the proximal third of the tibia and fibula. The mass invaded the medullary cavity and had a necrotic centre. Multiple nodular metastases (0.5-1.5 cm) were present in the liver, lungs and spleen. Histologically, the neoplasm was characterized by pleomorphic cells with indistinct boundaries, many multinucleated cells, necrosis and tissue invasion. There was intense cytoplasmic immunolabelling of neoplastic cells for vimentin and moderate cytoplasmic and nuclear labelling for human muscle actin, human smooth muscle actin and lysozyme. Immunolabelling for Iba1, CD18, CD1A, cytokeratin AE1/AE3, glial fibrillary acidic protein and desmin was negative. To our knowledge, this is the first report of an undifferentiated pleomorphic sarcoma in this species.

Cutaneous Histiocytic Sarcoma with Giant Cells in a Free-ranging Brush Rabbit (Sylvilagus bachmani)

A cutaneous mass in a free-ranging brush rabbit (Sylvilagus bachmani) was composed of neoplastic spindle to polygonal cells with multinucleated giant cells, which were positive for CD204 and negative for smooth muscle actin and desmin. Histiocytic sarcoma with giant cells was diagnosed; this neoplasm has not been reported previously in free-ranging lagomorphs.

Use of cutting-edge RNA-sequencing technology to identify biomarkers and potential therapeutic targets in canine and feline cancers and other diseases

With the growing interest in companion animals and the rapidly expanding animal healthcare and pharmaceuticals market worldwide. With the advancements in RNA-sequencing (RNA-seq) technology, it has become a valuable tool for understanding biological processes in companion animals and has multiple applications in animal healthcare. Historically, veterinary diagnoses and treatments relied solely on clinical symptoms and drugs used in human diseases. However, RNA-seq has emerged as an effective technology for studying companion animals, providing insights into their genetic information. The sequencing technology has revealed that not only messenger RNAs (mRNAs) but also non-coding RNAs (ncRNAs) such as long ncRNAs and microRNAs can serve as biomarkers. Based on the examination of RNA-seq applications in veterinary medicine, particularly in dogs and cats, this review concludes that RNA-seq has significant potential as a diagnostic and research tool. It has enabled the identification of potential biomarkers for cancer and other diseases in companion animals. Further research and development are required to maximize the utilization of RNA-seq for improved disease diagnosis and therapeutic targeting in companion animals.

Effect of needle gauge on pain and specimen quality of ultrasound-guided fine needle sampling without aspiration of the canine spleen

Modifications of splenic parenchyma are common ultrasonographic findings in dogs. Splenic fine needle aspiration (FNA) is a rapid, safe procedure, routinely performed in veterinary institutions. However, 22-gauge (G) needle usually reported is selected according to general practice and the most appropriate needle size to be used remains unclear. The aim of this prospective, single-center, methods comparison study was to assess the effect of needle size on cytologic specimens' evaluation and animal welfare during the procedure. Dogs underwent ultrasound-guided splenic FNA using 23, 25, and 27G needles. Needles were compared based on initial and then detailed cytologic evaluation. The initial evaluation assessed overall cellularity, cell preservation, hemodilution, and detailed cytologic evaluation referred to exhaustive splenic components. Welfare evaluation was performed based on a scoring system. A total of 54 dogs were included in this study with 54 of 54 welfare evaluations and 35 of 54 cytologic evaluations by one or two European College of Veterinary Clinical Pathology-certified cytologists. The final cytologic diagnosis was unchanged regardless of the needle size. For the initial evaluation, 23G needles provided significantly higher cellularity than the 27G needles. For detailed cytologic evaluation, only the richness in mesothelial cells and stroma was affected by needle size. Pain induced by the procedures was considered low using 23, 25, and 27G needles with the 27G needle producing the least adverse reactions. Findings from the current study supported using needle gauges smaller than the previously published standard 22G needle for spleen ultrasound-guided fine needle nonaspiration in dogs. Due to higher cellularity and lower pain scores, authors recommend the use of 23G needles with a nonaspiration technique.

Serum level of apoptosis inhibitor of macrophage in dogs with histiocytic sarcoma and its association with the disease

Histiocytic sarcoma (HS) is a rare neoplasm of macrophages or dendritic cells with a poor prognosis in dogs. As the apoptosis inhibitor of macrophage (AIM) is characteristically expressed in canine macrophages, we hypothesised that AIM is involved in the development or progression of HS in dogs. In this study, AIM expression in the tumour region and serum AIM levels in dogs with HS was assessed. Additionally, the effects of AIM overexpression on HS cell viability were investigated using a HS cell line that was selected from five validated HS cell lines. Immunohistochemistry showed that AIM expression was observed in the cytoplasm of the HS cells. CD36, a candidate AIM receptor, was also observed on the cell membrane of HS cells. When the serum AIM level was detected in 36 dogs with HS and 10 healthy dogs via western blot analysis, the AIM levels in the HS dogs were significantly higher than those in the controls. AIM mRNA expression in the 5 HS cell lines varied but was higher than that in the other tumour-derived lines. Among the five HS cell lines, DH82 originally had lower AIM and the highest CD36 expression. When AIM was overexpressed in DH82, therein cell growth speed and invasion, apoptosis inhibition and phagocytic activity were strongly upregulated. These data suggest that elevated intra-tumour expression of AIM could induce the progression of HS cells in dogs. Moreover, elevated serum AIM levels in dogs with HS could serve as a biomarker of HS.

Alternative Lengthening of Telomeres Is Rare in Canine Histiocytic Sarcoma

Cancer cells activate telomere maintenance mechanisms (TMMs) to overcome senescence and thus are targets for TMM-specific therapies. Telomerase-independent alternative lengthening of telomeres (ALT) is frequently utilized as a TMM in human sarcoma subtypes. Histiocytic sarcoma (HS) is a rare but aggressive tumor of hematopoietic origin with unknown ALT incidence in humans. ALT has been identified in canine HS, a tumor type comparable to human HS that occurs with high rates in certain canine breeds such as Bernese mountain dogs (BMDs). This retrospective study characterized the frequency of ALT in BMD and non-BMD patients diagnosed with HS as surrogates for humans. Formalin-fixed paraffin-embedded tumor samples from 63 dogs at two centers, including 47 BMDs, were evaluated for their ALT activity and relative telomere content (TC) using a radiolabel C-circle assay (CCA). Known ALT-positive samples served as controls. CCA-positive cases were validated via FISH. Two BMD samples showed ALT activity of 1-14% compared to controls. All other samples were ALT-negative. The TC did not correlate with the CCA results. ALT positivity was validated by the appearance of ultrabright telomere foci. Low ALT activity was present in 4% of BMDs with HS and therefore does not appear to be a common target for therapeutic approaches but can have diagnostic value.

Systemic histiocytic disorder in a jaguar (Panthera onca)

A 7-year-old captive female jaguar (Panthera onca) was presented with a 7-day history of dyspnoea and weight loss. Clinical examination revealed hepatomegaly and elevated serum alanine aminotransferase activity. Pulmonary ultrasonography revealed comet-tail images and an alveolar pattern was detected on thoracic radiography. Due to the poor prognosis, the jaguar was euthanized after 10 days. At necropsy, the main gross findings were hepatomegaly, splenomegaly and multifocal to coalescent, slightly elevated grey areas in the lungs. Histological examination revealed neoplastic proliferation of pleomorphic histiocytes arranged in cohesive sheets in the lungs, liver, spleen, kidneys and lymph nodes. Neoplastic cells had intense immunolabelling for vimentin and ionized calcium-binding adaptor molecule 1, and were immunonegative for pancytokeratin, E-cadherin, CD20, CD3 and CD79α. These findings were compatible with a systemic histiocytic disorder, distinct from any well-defined histiocytic proliferative disease in domestic animals.

Bilateral renal histiocytic sarcoma with disseminated lung involvement in a Siberian Forest Cat

Case summary

A 5-year-old female neutered Siberian Forest Cat presented with a 7-day history of lethargy, hyporexia and weight loss. Abdominal ultrasonography revealed bilateral renal changes suggestive of neoplasia. Thoracic radiography documented diffuse pulmonary nodules. The cat was euthanased during diagnostic investigations. Histopathological assessment and immunohistochemical staining of post-mortem renal biopsies were consistent with a histiocytic lesion, most likely histiocytic sarcoma (HS). The lung lesions were suspected of representing disseminated disease.

Relevance and novel information

HS is considered a rare neoplastic process in cats. This report describes a case of feline bilateral renal HS with suspected concomitant pulmonary involvement. A primary renal origin was suspected, with the lung lesions being a result of disseminated disease. Renal HS should be included as a differential diagnosis when renal ultrasonography reveals changes suggestive of neoplasia.

Functional Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) Delivered by Canine Histiocytic Sarcoma Cells Persistently Infected with Engineered Attenuated Canine Distemper Virus

The immune response plays a key role in the treatment of malignant tumors. One important molecule promoting humoral and cellular immunity is granulocyte-macrophage colony-stimulating factor (GM-CSF). Numerous successful trials have led to the approval of this immune-stimulating molecule for cancer therapy. However, besides immune stimulation, GM-CSF may also accelerate tumor cell proliferation, rendering this molecule a double-edged sword in cancer treatment. Therefore, detailed knowledge about the in vitro function of GM-CSF produced by infected tumor cells is urgently needed prior to investigations in an in vivo model. The aim of the present study was to functionally characterize a persistent infection of canine histiocytic sarcoma cells (DH82 cells) with the canine distemper virus strain Onderstepoort genetically engineered to express canine GM-CSF (CDV-Ond^neon-GM-CSF). The investigations aimed (1) to prove the overall functionality of the virally induced production of GM-CSF and (2) to determine the effect of GM-CSF on the proliferation and motility of canine HS cells. Infected cells consistently produced high amounts of active, pH-stable GM-CSF, as demonstrated by increased proliferation of HeLa cells. By contrast, DH82 cells lacked increased proliferation and motility. The significantly increased secretion of GM-CSF by persistently CDV-Ond^neon-GM-CSF-infected DH82 cells, the pH stability of this protein, and the lack of detrimental effects on DH82 cells renders this virus strain an interesting candidate for future studies aiming to enhance the oncolytic properties of CDV for the treatment of canine histiocytic sarcomas.

Combined immunohistochemical protocols to differentiate macrophages within the mononuclear-phagocyte system

BACKGROUND

The "mononuclear phagocyte system" (MPS) refers to dispersed mononuclear monocytes and macrophages and is used to distinguish them from polymorphonuclear cells. The term "histiocyte" indicates large cells with voluminous granulated cytoplasm, sometimes containing engulfed particles, recognized as fully differentiated end cells of the MPS. Dendritic cells (DC) represent another diversified population whose inclusion in the MPS is still debated. The diverse cells of the MPS cannot all be characterized by single antigen markers or unique functions expressed at all stages of cell differentiation or activation. Nevertheless, in a diagnostic setting, their reliable identification plays a major role when a specific therapy must be established. Understanding the heterogeneity among MPS cell populations is indeed relevant to define different therapeutic approaches that can range from the use of antibiotics to immunomodulatory agents. For this reason, we attempted to establish a protocol to reliably identify the proportion of macrophages within the mononuclear phagocyte system in a tissue and/or in a given inflammatory population.

METHODS

the Tafuri method was used in different double immunofluorescence protocols using an anti-Iba-1, anti-MAC387, and anti-CD11b-CD68-CD163-CD14-CD16 antibody.

RESULTS AND DISCUSSION

in normal canine skin the anti-Iba-1 antibody stained an epidermal cell population (i.e. Langerhans cells) and scattered cells within the dermal compartment. MAC387 was unable to stain cells containing Leishmania amastigotes in leishmaniasis-diagnosed samples as the anti-CD11b-CD68-CD163-CD14-CD16 antibody did. By using a combination of staining protocols to differentiate macrophages within the whole histiocytic infiltrate we validated the use of a cocktail of rabbit monoclonal antibodies raised against CD11b, CD68, CD163, CD14, CD16 to stain skin macrophages.

Characterization of expression and prognostic implications of GD2 and GD3 synthase in canine histiocytic sarcoma

GD2 and GD3 are disialoganglioside oncofetal antigens important in oncogenesis. GD2 synthase (GD2S) and GD3 synthase (GD3S) are needed for GD2 and GD3 production. The objectives of this study are to validate the use of RNA in situ hybridization (RNAscope®) in the detection of GD2S and GD3S in canine histiocytic sarcoma (HS) in vitro and optimize this technique in canine formalin-fixed paraffin-embedded (FFPE) tissues. A secondary objective is to evaluate the prognostic significance of GD2S and GD3S on survival. Quantitative RT-PCR compared GD2S and GD3S mRNA expression between three HS cell lines followed by RNAscope® in fixed cell pellets from the DH82 cell line and FFPE tissues. Variables prognostic for survival were determined with Cox proportional hazard model. RNAscope® was validated for detection of GD2S and GD3S and optimized in FFPE tissues. GD2S and GD3S mRNA expression was variable between cell lines. GD2S and GD3S mRNA expression was detected and measured in all tumor tissues; there was no association with prognosis. GD2S and GD3S are expressed in canine HS and successfully detected using the high throughput technique of RNAscope® in FFPE samples. This study provides the foundation for future prospective research of GD2S and GD3S utilizing RNAscope®.

Disseminated histiocytic sarcoma in a squirrel monkey (Saimiri sciureus)

A 14-years-old squirrel monkey was euthanized due to weakness. Histopathological examination revealed multifocal growth of oval cells with severe atypia in the liver, spleen, and bone marrow. The neoplastic cells were positive for histiocytic markers (Iba1, HLA-DR, CD204). This is the fourth case of histiocytic sarcoma in non-human primates.

Characterization of expression and prognostic implications of transforming growth factor beta, programmed death-ligand 1, and T regulatory cells in canine histiocytic sarcoma

Histiocytic sarcoma (HS) is an aggressive malignant neoplasm in dogs. Expression and prognostic significance of transforming growth factor beta (TGF-β), programmed death-ligand 1 (PD-L1), and T regulatory cells (Tregs) in HS is unknown. The goal of this study was to investigate the expression and prognostic significance of TGF-β, PD-L1, and FoxP3/CD25 in canine HS utilizing RNA in situ hybridization (RNAscope®). After validation was performed, RNAscope® on formalin-fixed paraffin-embedded (FFPE) patient HS tissue samples was performed for all targets and expression quantified with HALO® software image analysis. Cox proportional hazard model was conducted to investigate the association between survival time and each variable. Additionally, for categorical data, the Kaplan-Meier product-limit method was used to generate survival curves. TGF-β and PD-L1 mRNA expression was confirmed in the DH82 cell line by reverse transcription polymerase chain reaction (RT-PCR) and CD25 + FoxP3 + cells were detected by flow cytometry in peripheral blood. Once the RNAscope® method was validated, TGF-β H-score and dots/cell and FoxP3 dots/cell were assessed in HS samples and found to be significantly correlated with survival. Moderate positive correlations were found between FoxP3 and PD-L1 H-score, percent staining area, and dots/cell, and FoxP3 and TGF-β dots/cell. In summary, RNAscope® is a valid technique to detect TGF-β and PD-L1 expression and identify Tregs in canine HS FFPE tissues. Furthermore, canine HS expresses TGF-β and PD-L1. Increased TGF-β and FoxP3 correlated with worse prognosis. Prospective studies are warranted to further investigate TGF-β, PD-L1, and Tregs effect on prognosis.

Histological evidence of superficial inflammation is associated with lower recurrence of equine sarcoids following surgical removal: A follow-up study of 106 tumours in 64 horses

Although the equine sarcoid is the most common skin neoplasm in domesticated horses, histopathological characteristics have not previously been evaluated for association with recurrence. The aim of this retrospective cohort study was to investigate clinical and histopathological features of excised equine sarcoids and to evaluate their association with recurrence at the original surgical site and at new sites. Clinical records and excisional biopsies from 106 equine sarcoids from 64 horses referred to Leahurst Equine Hospital, University of Liverpool, between March 2010 and February 2015 were retrieved. Biopsies were re-evaluated histologically. Clinical data were obtained from hospital records, and owner-reported follow-up data were obtained by telephone questionnaire. Associations between clinical and histopathological features of sarcoids and their recurrence at the surgical site were determined using uni- and multivariable mixed effects logistic regression. Recurrence of sarcoids at the surgical site occurred in 30 horses (46.9%). Sarcoids developed at a distant site in 21 horses (32.8%). In the final mixed effects logistic regression model, only superficial inflammation was associated with reduced odds of recurrence at the surgical site (adjusted odds ratio, 0.32; 95% confidence intervals, 0.10-0.96; P = 0.04). This suggests that the inflammatory process may play a role in protecting horses against the recurrence of sarcoids.

Age at cancer diagnosis by breed, weight, sex, and cancer type in a cohort of more than 3,000 dogs: Determining the optimal age to initiate cancer screening in canine patients

The goal of cancer screening is to detect disease at an early stage when treatment may be more effective. Cancer screening in dogs has relied upon annual physical examinations and routine laboratory tests, which are largely inadequate for detecting preclinical disease. With the introduction of non-invasive liquid biopsy cancer detection methods, the discussion is shifting from how to screen dogs for cancer to when to screen dogs for cancer. To address this question, we analyzed data from 3,452 cancer-diagnosed dogs to determine the age at which dogs of certain breeds and weights are typically diagnosed with cancer. In our study population, the median age at cancer diagnosis was 8.8 years, with males diagnosed at younger ages than females, and neutered dogs diagnosed at significantly later ages than intact dogs. Overall, weight was inversely correlated with age at cancer diagnosis, and purebred dogs were diagnosed at significantly younger ages than mixed-breed dogs. For breeds represented by ≥10 dogs, a breed-based median age at diagnosis was calculated. A weight-based linear regression model was developed to predict the median age at diagnosis for breeds represented by ≤10 dogs and for mixed-breed dogs. Our findings, combined with findings from previous studies which established a long duration of the preclinical phase of cancer development in dogs, suggest that it might be reasonable to consider annual cancer screening starting 2 years prior to the median age at cancer diagnosis for dogs of similar breed or weight. This logic would support a general recommendation to start cancer screening for all dogs at the age of 7, and as early as age 4 for breeds with a lower median age at cancer diagnosis, in order to increase the likelihood of early detection and treatment.

Histiocytic sarcoma with central nervous system involvement in 6 cats

Here we characterize 6 cases (4 autopsies and 2 biopsies) of histiocytic sarcoma in the CNS of cats. All affected cats had chronic, progressive clinical signs. Three autopsied cats were euthanized because of a poor prognosis, and one died. The clinical outcome for the biopsy cases remains unknown. Tumors occurred in the brain (4 cases), spinal cord (1 case), and brain and spinal cord (1 case). Neoplasms were restricted to the CNS in 3 cases. Reported gross changes in the 4 autopsy cases consisted of neuroparenchymal swelling with or without tissue pallor or gray discoloration (2 cases) and a yellow or dark-gray mass (2 cases). Histologically, pleomorphic, round-to-elongate neoplastic cells with typical histiocytic morphology effaced the neuroparenchyma and leptomeninges. Multinucleate neoplastic cells were observed in all cases. The mitotic count was 1-24 in 2.37 mm2 (10 FN22 40× fields). Neoplastic cells in all cases had positive immunolabeling for Iba1; immunolabeling was negative for E-cadherin, CD3, CD79, and MUM1, confirming their histiocytic origin.

An Overview of Epithelial-to-Mesenchymal Transition and Mesenchymal-to-Epithelial Transition in Canine Tumors: How Far Have We Come?

Historically, pre-clinical and clinical studies in human medicine have provided new insights, pushing forward the contemporary knowledge. The new results represented a motivation for investigators in specific fields of veterinary medicine, who addressed the same research topics from different perspectives in studies based on experimental and spontaneous animal disease models. The study of different pheno-genotypic contexts contributes to the confirmation of translational models of pathologic mechanisms. This review provides an overview of EMT and MET processes in both human and canine species. While human medicine rapidly advances, having a large amount of information available, veterinary medicine is not at the same level. This situation should provide motivation for the veterinary medicine research field, to apply the knowledge on humans to research in pets. By merging the knowledge of these two disciplines, better and faster results can be achieved, thus improving human and canine health.

The Analysis of E-Cadherin, N-Cadherin, Vimentin, HER-2, CEA, CA15-3 and SF Expression in the Diagnosis of Canine Mammary Tumors

Canine mammary tumors (CMTs) are one of the most common tumors in female dogs, and they are associated with a poor prognosis owing to their high rate of recurrence and metastasis rates, which make their diagnosis especially important in clinical veterinary medicine. In this study, the characteristics of tumors were observed in dogs suffering from CMTs, and clinical diagnosis and histopathology were used to identify tumors. Furthermore, the expression levels of tumor markers for CMTs were analyzed by enzyme-linked immunosorbent assay (ELISA) and quantitative PCR (qPCR). Upon clinical examination, dogs with CMTs displayed a distinct and irregular mass in the mammary gland, and X-ray (Latero-lateral and ventro-dorsal views) and ultrasonography of the abdomen revealed a moderately echogenic mass at the mammary gland with slightly stronger density than the surrounding tissue. A total of 30 tumors were identified by histopathology, 11 benign and 19 malignant. Changes in some indicators in dogs suffering from CMTs and healthy dogs suggested that there were multiple direct or paraneoplastic changes associated with tumors that could be detected/suspected by hematological examination, and ELISA revealed the HER-2 serum concentrations were significantly different between healthy animals and those with malignant tumors. qPCR indicated that tumor markers N-cadherin, Vimentin, HER-2, CEA, CA15-3 and SF were higher in dogs with malignant tumors than healthy dogs, with a low level of E-cadherin in malignant tumors. This study verified that serological tests and molecular biological tests were essential to the early diagnosis, treatment and prognosis of dogs with tumors.

Atypical Lesions in Canine Leishmaniosis: Description of New Cases

Simple Summary

Canine leishmaniosis is a zoonotic disease caused mainly by the protozoan Leishmania infantum that is endemic in the Mediterranean basin. The clinical signs and pathological characteristics have been extensively described; however, atypical lesions leading to clinical and pathological misdiagnosis have been sporadically reported. This study presents three cases of dogs experimentally infected with Leishmania infantum that showed gross lesions considered atypical of canine leishmaniosis and not previously reported. Macroscopic lesions were observed in the liver, spleen, and peritoneal cavity that corresponded to tan to whitish nodular lesions in all organs and multifocal irregular and linear whitish lesions in one of the livers that mimicked tumors. Microscopically, a marked granulomatous inflammation with a relative scarcity of parasites was observed in all the organs. In conclusion, microscopic and parasitological studies should be performed on atypical lesions observed in Leishmania-infected and non-infected dogs, especially in endemic regions. In addition, due to its zoonotic importance, leishmaniosis should be considered when atypical nodular lesions are observed in dogs from non-endemic regions with a history of travel to endemic regions.

Abstract

Pathological characteristics are well described in canine leishmaniosis (CanL). However, atypical lesions that can be confused with other pathologies or trigger unusual clinical signs are sporadically reported. Atypical lesions were observed during routine postmortem examination in three Leishmania-infected dogs and samples were taken for histopathological and immunohistochemical studies. Clinical signs, biochemical parameters, level of antibodies, and parasite detection by PCR were also evaluated. Atypical lesions were found in the peritoneal cavity, liver, and spleen. Splenomegalia and hepatomegalia were observed in all dogs. In addition, multifocal dark to white nodules of variable size were observed in the peritoneal cavity, liver, and spleen of one dog and in the spleen of the other two dogs. One dog presented diffuse irregular whitish lines with a threadlike appearance and another an intense fibrotic depression in the intermediate lobe. Microscopically, an intense granulomatous inflammation with abundant macrophages, a variable number of lymphocytes, and a low to moderate number of parasites was observed. This study represents the first description of granulomatous peritonitis associated with Leishmania in dogs. It also shows atypical macroscopic expression of hepatitis in CanL. In the absence of an adequate clinical history and laboratory analyses, certain lesions observed in CanL could admit alternative diagnoses.

Comparative Evaluation of Tumor-Infiltrating Lymphocytes in Companion Animals: Immuno-Oncology as a Relevant Translational Model for Cancer Therapy

Despite the important role of preclinical experiments to characterize tumor biology and molecular pathways, there are ongoing challenges to model the tumor microenvironment, specifically the dynamic interactions between tumor cells and immune infiltrates. Comprehensive models of host-tumor immune interactions will enhance the development of emerging treatment strategies, such as immunotherapies. Although in vitro and murine models are important for the early modelling of cancer and treatment-response mechanisms, comparative research studies involving veterinary oncology may bridge the translational pathway to human studies. The natural progression of several malignancies in animals exhibits similar pathogenesis to human cancers, and previous studies have shown a relevant and evaluable immune system. Veterinary oncologists working alongside oncologists and cancer researchers have the potential to advance discovery. Understanding the host-tumor-immune interactions can accelerate drug and biomarker discovery in a clinically relevant setting. This review presents discoveries in comparative immuno-oncology and implications to cancer therapy.

Identification of a Hypomorphic FANCG Variant in Bernese Mountain Dogs

Bernese mountain dogs (BMDs), have an overall cancer incidence of 50%, half of which is comprised of an otherwise rare tumor, histiocytic sarcoma (HS). While recent studies have identified driver mutations in the MAPK pathway, identification of key predisposing genes has been elusive. Studies have identified several loci to be associated with predisposition to HS in BMDs, including near the MTAP/CDKN2A region, but no causative coding variant has been identified. Here we report the presence of a coding polymorphism in the gene encoding FANCG, near the MTAP/CDKN2A locus. This variant is in a conserved region of the protein and appears to be specific to BMDs. Canine fibroblasts derived from dogs homozygous for this variant are hypersensitive to cisplatin. We show this canine FANCG variant and a previously defined hypomorphic FANCG allele in humans impart similar defects in DNA repair. However, our data also indicate that this variant is neither necessary nor sufficient for the development of HS. Furthermore, BMDs homozygous for this FANCG allele display none of the characteristic phenotypes associated with Fanconi anemia (FA) such as anemia, short stature, infertility, or an earlier age of onset for HS. This is similar to findings in FA deficient mice, which do not develop overt FA without secondary genetic mutations that exacerbate the FA deficit. In sum, our data suggest that dogs with deficits in the FA pathway are, like mice, innately resistant to the development of FA.

Cannabinoid receptors in the inflammatory cells of canine atopic dermatitis

Background

Atopic dermatitis (AD) is one of the most common cutaneous inflammatory and pruritic diseases in dogs. Considering its multifactorial nature, AD can be a challenging disease to manage, and the therapeutic strategy must often be multimodal. In recent years, research has been moving toward the use of natural products which have beneficial effects on inflammation and itching, and no side effects. Cannabinoid receptors have been demonstrated to be expressed in healthy and diseased skin; therefore, one of the potential alternative therapeutic targets for investigating AD is the endocannabinoid system (ECS).

Objective

To immunohistochemically investigate the expression of the cannabinoid receptor type 2 (CB2R), and the cannabinoid-related receptors G protein-coupled receptor 55 (GPR55), transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1) in mast cells (MCs), macrophages, dendritic cells (DCs), T cells, and neutrophils of the skin of dogs with AD.

Animals

Samples of skin tissues were collected from eight dogs with AD (AD-dogs).

Materials and methods

The immunofluorescent stained cryosections of the skins of 8 dogs with AD having antibodies against CB2R, GPR55, TRPV1, TRPA1 were semiquantitatively evaluated. The inflammatory cells were identified using antibodies against tryptase (mast cells), ionized calcium binding adaptor molecule 1 (IBA1) (macrophages/DCs), CD3 (T cells), and calprotectin (neutrophils). The proportions of MCs, macrophages/DCs, T cells, and neutrophils expressing CB2R, GPR55, TRPV1 and TRPA1 were evaluated.

Results

The cells of the inflammatory infiltrate showed immunoreactivity (IR) for all or for some of the cannabinoid and cannabinoid-related receptors studied. In particular, MCs and macrophages/DCs showed CB2R-, GPR55-, TRPA1-, and TRPV1-IR; T cells showed CB2R-, GPR55- and TRPA1-IR, and neutrophils expressed GPR55-IR. Co-localization studies indicated that CB2R-IR was co-expressed with TRPV1-, TRPA1-, and GPR55-IR in different cellular elements of the dermis of the AD-dogs.

Conclusions and clinical importance

Cannabinoid receptor 2, and cannabinoid-related receptors GPR55, TRPV1 and TRPA1 were widely expressed in the inflammatory infiltrate of the AD-dogs. Based on the present findings, the ECS could be considered to be a potential therapeutic target for dogs with AD, and may mitigate itch and inflammation.

Tumour Incidence in Dogs in Germany: a Retrospective Analysis of 109,616 Histopathological Diagnoses (2014-2019)

Characterization of a tumour entity is based on the precise histopathological diagnosis taking into account the signalment of the diseased animal. The present study is a comprehensive, up-to-date statistical investigation on the type, frequency and breed distribution of neoplasia in dogs in Germany. The histopathological datasets of 109,616 German canine tissue samples (2014-2019) were processed and statistically examined in retrospect. Non-neoplastic diseases were found in 38,650 samples (35.3%) and 70,966 neoplasms (64.7%) were diagnosed. The most common neoplasms were mammary tumours (21.9%), benign epithelial skin tumours (15.4%), mast cell tumour (9.7%), histiocytoma (7.0%), soft tissue sarcoma (5.8%), lipoma (5.8%), melanocytic tumours (5.2%) and odontogenic tumours (4.7%). In general, Beagles, Magyar Vizslas, Boxers, Schnauzers, Spaniels, French Bulldogs and Golden Retrievers had an increased risk of neoplasia (odds ratio 1.17-1.46; all: P ≤0.001) compared with crossbreed dogs. In particular, Boxers, Golden Retrievers, Rottweilers and Schnauzers were often affected by malignant neoplasms, whereas some breeds (eg, West Highland White Terrier, Magyar Vizsla, Chihuahua, Dachshund and Yorkshire Terrier) were frequently affected by numerous benign tumour types. Despite the known risk of haemangiosarcoma in German Shepherd Dogs, other malignant tumours were rare in this breed. Depending on the type of tumour, some purebred dog breeds can have an increased, reduced or identical risk for certain neoplasms compared with crossbreeds. Discussion of breed predispositions to tumour diseases must therefore be conducted critically and with a view to clinical relevance.

mRNA sequencing analysis and growth inhibitory effects of palbociclib on cell lines from canine histiocytic proliferative disorders

Canine histiocytic proliferative disorders include aggressive and fatal diseases, such as histiocytic sarcoma (HS) and histiocytosis (SyH). The molecular mechanisms underlying cell proliferation need to be elucidated for the development of effective treatments. In the present study, mRNA expression levels were comprehensively analysed in cell lines derived from localized HS, disseminated HS, SyH and Langerhans cell histiocytosis (LCH) in dogs. Based on the results obtained, the growth inhibitory effects of palbociclib, a CDK4/6 inhibitor, were verified with the cell lines in vitro and in xenograft mouse model. Hierarchical clustering and principal component analysis plots of mRNA expression profiles divided the cell lines into three groups: a localized HS group, disseminated HS/SyH group, and LCH. The results of an ingenuity pathway analysis suggested that the MAPK signalling pathway was activated in the localized HS and LCH cell lines, and the PI3K signalling pathway in the disseminated and localized HS cell lines. In all cell lines, the expression of the tumour suppressor genes TP53, CDKN2A and CDKN1A was down-regulated, whereas that of Rb was preserved. In vitro assessments revealed the growth inhibitory effects of palbociclib in all cell lines examined. In a xenograft mouse model using a cell line from disseminated HS, palbociclib exerted significant growth inhibitory effects. These results suggest the potential of palbociclib as a therapeutic drug candidate for the treatment of malignant histiocytic proliferative disorders of the dog.

Disseminated Histiocytic Sarcoma in Two Free-Living Florida Manatees (Trichechus manatus latirostris)

During necropsy of two manatees, masses in multiple organs including liver and spleen were identified. They were composed of neoplastic round to spindle-shaped cells, positive for vimentin, Iba-1, lysozyme, and Mac387, consistent with histiocytic sarcoma. One manatee also had an undifferentiated sarcoma that may have arisen from the histiocytic sarcoma.

Canine idiopathic orbital inflammation: A case series of four affected dogs (five orbits)

PURPOSE

In humans, idiopathic orbital inflammation (IOI) is a diagnosis attributed to benign, inflammatory orbital conditions without identifiable local or systemic cause. We describe the clinical signs, imaging and histopathological findings, management and outcome of four dogs diagnosed with IOI.

METHODS

Multicentric retrospective study.

RESULTS

A total of four dogs (five orbits) of three different breeds (three cases were English Springer Spaniels [ESS] or ESS-cross) and ages ranging from 3 to 12 years were included. Initial presenting signs were unilateral and included exophthalmos, enophthalmos, globe deviation, thickening and protrusion of the third eyelid and conjunctival hyperemia. Computed tomography and magnetic resonance imaging identified heterogeneous space-occupying, contrast-enhancing orbital lesions in all cases. Sparing of the retrobulbar space was detected in four of five orbits. Histopathology revealed mixed inflammatory infiltrates of lymphocytes, plasma cells, and histiocytes. Immunohistochemistry was performed in two cases highlighting the presence of histiocytes and lymphocytes, predominantly T cells. Resolution of clinical signs was achieved in two cases managed with oral immunosuppressant medication (corticosteroids alone or combined with cyclosporine or azathioprine), one went into spontaneous remission, one resolved with topical corticosteroids, and one underwent exenteration. Recurrence occurred in two cases within 15 months of initial diagnosis and required further immunosuppressant medication. One case developed signs in the contralateral orbit within 8 months of presentation.

CONCLUSIONS

IOI is an uncommon condition in dogs. Its diagnosis relies on the combination of advanced imaging and histology. As in humans, it appears that spontaneous remission and recurrence may occur requiring long-term immunosuppressant medication.

Review of diagnostic histologic features of cutaneous round cell neoplasms in dogs

Cutaneous round cell neoplasms (RCNs) are among the most common skin tumors of dogs. Although a diagnosis can be made in most cases following the examination of H&E-stained routine samples, less-differentiated neoplasms can exhibit overlapping morphologic features that may be challenging to the pathologist, and require immunohistochemistry or molecular testing to reach a final diagnosis. Many patients with cutaneous RCNs are initially seen by a general practitioner and are not referred to a veterinary teaching hospital until a diagnosis has been made. For this reason, anatomic pathology residents at some academic or other training institutions may not be exposed frequently to RCNs during the surgical biopsy service as part of their residency training. In an attempt to fill that gap, here we review the key routine histologic features of canine cutaneous RCNs.