Acanthomatous ameloblastoma with mucinous glandular differentiation in a dog

This report describes an atypical case of canine acanthomatous ameloblastoma (CAA) with mucinous glandular differentiation in a 12-year-old male Chihuahua with a right mandibular mass. Initially diagnosed as CAA by biopsy, computed tomography revealed bone lysis, prompting surgical excision. Histological examination showed lobular growth with two distinct neoplastic cell populations: typical CAA-like cells and a minor glandular structure population. Mucinous glandular differentiation in CAA is undocumented in veterinary literature. Immunohistochemistry showed positivity for cytokeratin AE1/AE3 in all tumor cells, and cytokeratin CAM5.2 and Alcian blue staining confirmed glandular cells and mucin. A low mitotic and K-i67 proliferation index suggested low-grade malignancy. This rare case highlights the need for comprehensive histopathological and immunohistochemical analysis to distinguish CAA from other oral tumors.

Orbital reconstruction: titanium mesh implant after excision of orbitozygomaticomaxillary tumors

Pathologic lesions of the orbitozygomaticomaxillary complex (OZMC) and caudal oral cavity can be a challenge in veterinary oromaxillofacial surgery. Neoplastic lesions that are in close proximity to or invading the orbit may result in significant loss of structural integrity after curative intent surgery. This in turn may alter the topography of the bulbous oculi (globe) with resultant enophthalmos, diplopia, and entropion. Historically, orbital exenterations have been deemed a suitable option to avoid these complications. However, lesions that do not include the globe in the surgical margin may be overtreated by irreversible orbital exenterations. Orbital reconstruction methods that ameliorate these consequences could be advantageous. A novel approach to reconstruct the orbit with a titanium mesh implant is described and the clinical and ophthalmic outcomes reported.

Tumor Immune Microenvironment and Its Clinicopathological and Prognostic Associations in Canine Splenic Hemangiosarcoma

Tumor cells can induce important cellular and molecular modifications in the tissue or host where they grow. The idea that the host and tumor interact with each other has led to the concept of a tumor microenvironment, composed of immune cells, stromal cells, blood vessels, and extracellular matrix, representing a unique environment participating and, in some cases, promoting cancer progression. The study of the tumor immune microenvironment, particularly focusing on the role of tumor-infiltrating lymphocytes (TILs), is highly relevant in oncology due to the prognostic and therapeutic significance of TILs in various tumors and their identification as targets for therapeutic intervention. Canine splenic hemangiosarcoma (HSA) is a common tumor; however, its immune microenvironment remains poorly understood. This retrospective study aimed to characterize the histological and immunohistochemical features of 56 cases of canine splenic HSA, focusing particularly on tumor-infiltrating lymphocytes (TILs). We assessed the correlations between the lymphocytic response, the macroscopic and histological characteristics of the tumor, and the survival data. Our study demonstrated that FoxP3 distribution was associated with tumor-related death and survival, while the CD20 count was associated with metastasis. This study provides an in-depth characterization of the tumor immune microenvironment in canine splenic HSA and describes potential prognostic factors.

Confirmation of canine acanthomatous ameloblastoma using RAS Q61R immunohistochemical staining of formalin-fixed paraffin-embedded tissues

Differentiating canine acanthomatous ameloblastoma (CAA) from oral squamous cell carcinoma (OSCC) based on routine histopathology can be challenging. We have previously shown that more than 95% of CAAs harbor an HRAS p.Q61R somatic mutation, while OSCCs carry either wild-type alleles or other MAPK pathway activating mutations (e.g., HRAS p.Q61L, BRAF p.V595E). Given that HRAS p.Q61R mutations are highly prevalent in CAA, we hypothesized that a RAS Q61R-specific rabbit monoclonal antibody may be a useful tool for confirmation of CAA by immunohistochemical (IHC) staining. In the present study, we assessed IHC staining of archived formalin-fixed and paraffin-embedded biopsy samples with a diagnosis of CAA (n = 23), using a RAS Q61R-specific rabbit monoclonal antibody (SP174) and an automated IHC stainer. Negative control samples consisted of HRAS p.Q61R mutation-negative OSCC tumors with either a known HRAS p.Q61L mutation (n = 1), BRAF p.V595E mutation (n = 4), or wild-type corresponding alleles (n = 3). We found that all 23 CAAs showed diffuse and strong membranous RAS Q61R immunoreactivity (100% sensitivity), while none of the 8 OSCCs showed immunoreactivity (100% specificity). The data supports the use of RAS Q61R-specific rabbit monoclonal antibody for diagnostic IHC confirmation of CAA and ruling out OSCC in dogs.

Maxillary neoplasms in four dromedary camels

Four camels (Camelus dromedarius) presented to the Veterinary Teaching Hospital at King Faisal University with maxillary masses. On radiographs, the masses were multicystic and expanded the maxillary bone. The tumors were diagnosed by histopathologic examination as conventional ameloblastoma, two cases as intraosseous squamous cell carcinoma, and central odontogenic fibroma with ossification. To the authors' knowledge, this is the first report of ameloblastoma in a camel, the first detailed description of maxillary squamous cell carcinoma in camels, and the first report of central odontogenic fibroma in any animal species.

Histological Variants of Squamous and Basal Cell Carcinoma in Squamates and Chelonians: A Comprehensive Classification

In the present study, the histological characteristics of squamous cell carcinomas (SCCs) and basal cell carcinomas (BCCs) obtained from 22 squamate and 13 chelonian species were retrospectively evaluated. While the examined tissues were originally diagnosed as 28 SCCs and 7 BCCs based on histological evaluation by a specialty diagnostic service, eight SCCs could be re-classified as BCCs and three SCCs proved to be non-neoplastic lesions. In addition, all SCCs and BCCs were classified into distinct histological variants. The SCCs could be categorized as one SCC in situ, three moderately differentiated SCCs, seven well-differentiated SCCs, and six keratoacanthomas. BCCs were classified as five solid BCCs, four infiltrating BCCs, five keratotic BCCs, and one basosquamous cell carcinoma. In addition, the present study reports the occurrence of BCCs in seven reptile species for the first time. In contrast to what has been documented in humans, IHC staining with the commercially available epithelial membrane antigen and epithelial antigen clone Ber-EP4 does not allow differentiation of SCCs from BCCs in reptiles, while cyclooxygenase-2 and E-cadherin staining seem to have discriminating potential. Although the gross pathological features of the examined SCCs and BCCs were highly similar, each tumor could be unequivocally assigned to a distinct histological variant according to the observed histological characteristics. Based on the results of this study, a histopathological classification for SCCs and BCCs is proposed, allowing accurate identification and differentiation of SCCs and BCCs and their histological variants in the examined reptile species. Presumably, BCCs are severely underdiagnosed in squamates and chelonians.

Highly recurrent BRAF p.V595E mutation in canine papillary oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most common oral epithelial malignancy in dogs. It exhibits locally aggressive biological behaviour with the potential to metastasize, and a reported 1-year survival rate of 0% when left untreated. Expression studies suggest that aberrant MAPK signalling plays a key role in canine OSCC tumorigenesis, which is consistent with BRAF and HRAS MAPK-activating mutations reported in some tumours. Several morphological subtypes of canine OSCC have been described, with papillary, conventional, and basaloid as the most common patterns. We hypothesized that mutational differences may underlie these phenotypic variations. In this study, targeted Sanger sequencing and restriction fragment length polymorphism assays demonstrate that up to 85.7% of canine papillary OSCC (n = 14) harbour a BRAF p.V595E mutation. Assessment of neoplastic epithelial cell proliferation using Ki67 immunolabelling (n = 10) confirmed a relatively high proliferation activity, consistent with their known aggressive clinical behaviour. These findings underscore a consistent genetic feature of canine papillary OSCC and provide a basis for the development of novel diagnostic and targeted therapeutic approaches that can improve the quality of veterinary care.

p-S6 as a Prognostic Biomarker in Canine Oral Squamous Cell Carcinoma

Scarce information exists on the role of mTOR pathway proteins and their association to aggressiveness and prognosis of patients with canine oral cancers. We aimed to investigate the activated form of mTOR and its downstream S6 protein in canine oral squamous cell carcinoma (OSCC), and to evaluate potential associations between protein expression and clinic-pathologic variables and survival. For that we analysed p-mTOR and p-S6 protein expression by immunohistochemistry in 61 canine OSCCs. Multivariate analysis was conducted to examine their role in patients’ cancer-specific survival (CSS). p-mTOR and p-S6 expression were present in almost all cases. High-expression of p-mTOR was observed in 44 (72.1%) cases using extent score and 52 (85.2%) cases using intensity score. For p-S6, high expression was observed in 53 (86.9%) cases using extent score and in 54 (88.5%) cases using intensity score. An independent prognostic value for p-S6 extension (p = 0.027), tumour stage (p = 0.013) and treatment (p = 0.0009) was found in patients’ CSS analysis. Our data suggest that p-mTOR and p-S6 proteins are commonly expressed in canine OSCC and p-S6 expression is correlated with poor CSS in dogs with OSCC. More studies should be performed to identify possible therapeutic targets related with mTOR pathway for these patients.

Morphological and immunohistochemical characterization and molecular classification of spontaneous mammary gland tumors in macropods

Mammary gland neoplasms in macropods are uncommonly reported, and the morphological and immunohistochemical characteristics are incompletely described. The goal of this study was to describe the morphologic features of macropod mammary neoplasms and to determine the molecular subtypes of mammary carcinomas using a panel of antibodies against estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (Her-2), p63, smooth muscle actin (SMA), and epidermal growth factor receptor (EGFR). Biopsy and necropsy specimens were examined from 21 macropods with mammary tumors submitted to Northwest ZooPath from 1996 to 2019. In accordance with the histologic classification of canine mammary tumors proposed by Goldschmidt and colleagues, tubulopapillary (2), tubular (10), and comedo-carcinomas (2), adenoma (1), lobular hyperplasia (3), fibroadenomatous hyperplasia (1), and mastitis (2) were diagnosed. Red kangaroos (Osphranter rufus) were most commonly diagnosed with mammary carcinomas (79% of all carcinomas). Seven carcinomas had lymphovascular invasion and 2 also had pulmonary metastases. Six of these 7 carcinomas were classified as grade 3. Immunohistochemistry (IHC) for all antibodies was performed on 9/14 carcinomas, and partial IHC was performed for 3 cases. All 12 carcinomas were immunoreactive for PR, 5 for ER, 9 for EGFR, and none for Her-2. Five of the 9 mammary carcinomas with complete IHC data were classified as luminal A subtype, and 4 were normal-like subtype. Accurate classification of mammary tumors in macropods based on morphology, immunohistological characteristics, and molecular subtype may be helpful in guiding clinical management, prognosis, and potential therapeutic targets.

Cytologic features of an acanthomatous ameloblastoma in a dog

An 8-year-old mixed breed male dog was presented with a mass on the rostral mandibular gingiva that quickly emerged 2-3 weeks prior to presentation. The mass was firm, smooth, well-circumscribed, and approximately 2 × 1 × 0.5 cm in size rostral to the left mandibular canine tooth (304). Clinical examination and radiographs were unremarkable. Cytology revealed two distinct cell populations, consisting of numerous uniform-appearing epithelial cell clusters and low numbers of individual spindle cells. Epithelial cells had mild anisocytosis and anisokaryosis, round nuclei with finely stippled chromatin, no prominent nucleoli, high N:C ratios, and low amounts of pale basophilic cytoplasm. Slender spindle cells observed had oval nuclei with no prominent nucleoli and wispy cytoplasm. On histopathologic examination, the lamina propria of the gingiva was dissected by numerous irregular and anastomosing trabeculae and islands of neoplastic epithelial cells. Neoplastic cells were focally in connection with the hyperplastic overlying epithelium. The trabeculae were surrounded and embedded by cell-rich fibrous stroma. Peripheral to the islands and trabeculae, cells were arranged in palisades, and the nuclei had an antibasilar location. The epithelial cells had prominent intercellular bridges, low amounts of cytoplasm, and one round to oval nucleus. Anisocytosis and anisokaryosis were mild to moderate, and six mitoses/10 HPF were present. Tumor cells reached the deep sample margins. Histopathologic evaluation was consistent with acanthomatous ameloblastoma. This locally aggressive neoplasm causes alveolar bone lysis and often extends beyond alveolar bone margins. Acanthomatous ameloblastoma is an important differential for rostral mandibular gingival masses containing numerous uniform epithelial cell clusters with rare slender spindle cells.

Oral cancer in non-smoker non-drinker patients. Could comparative pet oncology help to understand risk factors and pathogenesis?

During the last decades there has been a progressive increase in proportion of incidence of oral cancer not related to a known etiologic factor, such as the so-called "oral cancer in young", a relevant tumor in non-smoker non-drinker (NSND) patients. The topic is matter of long standing debate, and adequate study models to analyze this entity are lacking. Spontaneous oral cancer in companion animals such as dogs and cats, presents more clinical and biological similarities with the human oral cancer than any other animal model. In our review we analyze how the study of spontaneous oral cancer in common pets can prospectively prove to be of double usefulness in unraveling the question about the origin of oral cancer in NSND patients, allowing both the analysis of environmental and behavioral risk factors, and the study of how carcinogenic viruses, chronic inflammation, and changes in immunity can influence pre-tumoral and tumoral microenvironment.

Histological and immunohistochemical investigation of canine prostate carcinoma with identification of common intraductal carcinoma component

A limited number of species, including men and dogs, spontaneously develop prostate cancer (PC). The histological and molecular relevance of canine PC as a model for the disease in men remains controversial. To address this challenge, this study aimed to assess the histomorphology and expression of basal cell, urothelial and neuroendocrine markers [p63, high molecular weight cytokeratin (HMWCK), Uroplakin 3 (UPIII), neuron‐specific enolase (NSE)] in canine PC (n = 41). Based on histomorphology, 10/41 (24%), 21/41 (51%) and 9/41 (22%) were classified as adenocarcinoma (AC), urothelial carcinoma (UC), and mixed carcinoma, respectively. Tumour inflammation was common, frequently severe [20/41 (49%)], and associated with neutering (p < .02) and urothelial differentiation (p < .02). Most (36/40, 90%) cancers contained only rare cells with basal cell marker expression or were negative. The expression of UPIII was absent or weak in the majority (33/38, 87%) of tumours, with moderate to strong staining in the remaining cases. NSE expression in PC was rare and limited to 2/14 (14%) cases. Tumour extension into benign ducts and glands was a common finding with presence in 17/39 (44%) of carcinomas with and without urothelial differentiation. In conclusion, we confirm that canine PC is characterized by absent or weak expression of basal cell and urothelial markers. Although rare, NSE expression, potentially indicating neuroendocrine differentiation, is reported for the first time in canine PCa. Intraductal carcinoma of the prostate with concurrent invasive PCa (IDCP‐inv) is a frequent, not previously described, finding in dogs with PC.

Molecular homology between canine spontaneous oral squamous cell carcinomas and human head-and-neck squamous cell carcinomas reveals disease drivers and therapeutic vulnerabilities

Spontaneously occurring canine oral squamous cell carcinomas (COSCC) are viewed as a useful model for human head and neck squamous cell carcinomas (HNSCC). To date however, the molecular basis of COSCC remains poorly understood. To identify changes pertinent to cancer cells in COSCC, we specifically analyzed tumor cells and matched normal epithelium from clinical formalin-fixed paraffin-embedded specimens using laser-capture-microdissection coupled with RNA-sequencing (RNAseq). Our results identify strong contributions of epithelial-to-mesenchymal transition (EMT), classical tumor-promoting (such as E2F, KRAS, MYC, mTORC1, and TGFB1 signaling) and immune-related pathways in the tumor epithelium of COSCC. Comparative analyses of COSCC with 43 paired tumor/normal HNSCC from The Cancer Genome Atlas revealed a high homology in transcriptional reprogramming, and identified processes associated with cell cycle progression, immune processes, and loss of cellular differentiation as likely central drivers of the disease. Similar to HNSCC, our analyses suggested a ZEB2-driven partial EMT in COSCC and identified selective upregulation of KRT14 and KRT17 in COSCC. Beyond homology in transcriptional signatures, we also found therapeutic vulnerabilities strongly conserved between the species: these included increased expression of PD-L1 and CTLA-4, coinciding with EMT and revealing the potential for immune checkpoint therapies, and overexpression of CDK4/6 that sensitized COSCC to treatment with palbociclib. In summary, our data significantly extend the current knowledge of molecular aberrations in COSCC and underline the potential of spontaneous COSCC as a model for HNSCC to interrogate therapeutic vulnerabilities and support translation of novel therapies from bench to bedside.

Treatment of canine oral papillary squamous cell carcinoma using definitive-intent radiation as a monotherapy-a case series

Canine oral papillary squamous cell carcinoma (COPSCC) is a rare neoplasm and although locally invasive it carries a favourable prognosis following wide surgical excision. Radiotherapy has been reported to be effective as an adjunct treatment to surgery. However, limited information is available on the role of radiotherapy as single treatment. This single‐institution retrospective study describes a series of 10 dogs diagnosed with macroscopic COPSCC that were treated with definitive‐intent radiotherapy (DRT) as a monotherapy. These dogs had a median age of 4 years (range: 0.4‐9.6 years). The tumour was located in the rostral oral cavity in all cases with a median tumour size of 2.5 cm (range: 0.8‐6.8 cm). No local or distant metastases were identified. All dogs were treated with electron beam DRT (>32Gy, 10‐16 daily fractions of 3.2Gy). The median follow‐up time was 961 days (range: 333‐3.498 days) with nine dogs achieving a complete response and one dog a partial response. The dog with the partial response developed disease progression at 228 days after initiation of radiotherapy. Two dogs died from non‐tumour‐related causes. The remaining seven dogs were still alive and in complete remission at the time of last follow‐up. Median progression‐free survival time and median survival time were not reached. DRT was generally well tolerated, but all dogs experienced self‐limiting acute radiation mucositis (grade 2‐3) and/or dermatitis (grade 1). No late radiation toxicity was observed. Macroscopic COPSCC appears to be a radiosensitive tumour that can be successfully treated with DRT eliminating the need for aggressive surgery in advanced cases.

Ki67 Labelling Index of Neoplastic Epithelial Cells Differentiates Canine Acanthomatous Ameloblastoma from Oral Squamous Cell Carcinoma

Canine acanthomatous ameloblastoma (CAA) and oral squamous cell carcinoma (OSCC) are the most common oral tumours of epithelial origin in dogs. Overlapping clinical, radiographical and histological features can make distinction between CAA and OSCC difficult. The ability to distinguish tumour identity is critical due to their different biological behaviour and recommended treatment modalities, as well as respective comparative and translational applications as potential models of human disease. Based on marked differences in biological behaviour (i.e. benign versus malignant), it is reasonable to predict that the tumour cell proliferation activity is lower in CAA than in OSCC. However, to our knowledge, the epithelial cell proliferation activity of CAA has not been studied or compared with that of OSCC. Therefore, the aims of this study were to (1) compare the neoplastic epithelial cell proliferation activity of CAA and OSCC based on conventional mitotic index (MI) and Ki67 labelling index (LI), and (2) correlate these findings with clinical parameters including patient signalment, anatomical tumour location and degree of local invasion at the time of diagnosis as determined by computed tomography. We found that (1) the Ki67 LI of OSSC (n = 14) was significantly higher than that of CAA (n = 25), (2) the Ki67 LI correlated with a more aggressive locally invasive behaviour, and (3) the MI was not associated with tumour type. We conclude that the Ki67 LI, but not the MI, is a useful differential marker of CAA from OSCC, and that the epithelial cell proliferation activities of OSCC and CAA correlate with their known differences in biological behaviour.

Immunohistochemical Features of Epithelial-Mesenchymal Transition in Feline Oral Squamous Cell Carcinoma

Feline oral squamous cell carcinoma (FOSCC) is an aggressive malignancy with invasive and metastatic behavior. It is poorly responsive to chemotherapy and radiation. Neoplastic epithelial-mesenchymal transition (EMT) portends highly malignant behavior and enhances resistance to therapy. In transitioning to a more malignant phenotype, carcinoma stem cells undergo transformation mediated by expression of proteins, endowing them with mesenchymal properties advantageous to cell survival. The goal of the current study was to identify proteins associated with EMT in FOSCC. This study documents protein expression patterns in 10 FOSCC biopsies and 3 FOSCC cell lines (SCCF1, SCCF2, SCCF3), compatible with an EMT phenotype. As markers of EMT, P-cadherin, N-cadherin, vimentin, nuclear transcription factors Twist and Snail, hypoxia inducible factor 1α (HIF-1α), programmed death ligand 1, and vascular endothelial growth factor D, as well as E-cadherin, were examined using immunohistochemistry, Western blot, and enzyme-linked immunosorbent assay. P-cadherin, Twist, HIF-1α, and programmed death ligand 1 were commonly expressed in biopsies and cell lines. N-cadherin, classically associated with EMT, was not highly expressed, and E-cadherin was coexpressed along with proteins characteristic of EMT in all specimens. Production of vascular endothelial growth factor A by cell lines, a process regulated by HIF-1α expression, was suppressed by the small-molecule inhibitor dasatinib. These data are consistent with EMT in FOSCC and shed light on cellular changes that could contribute to the aggressive behavior of FOSCC.

Ultra-frequent HRAS p.Q61R somatic mutation in canine acanthomatous ameloblastoma reveals pathogenic similarities with human ameloblastoma

Ameloblastoma is a locally aggressive odontogenic tumour that occurs in humans and dogs. Most ameloblastomas (AM) in humans harbour mutually-exclusive driving mutations in BRAF, HRAS, KRAS, NRAS or FGFR2 that activate MAPK signalling, and in SMO that activates Hedgehog signalling. The remarkable clinical and histological similarities between canine acanthomatous ameloblastoma (CAA) and AM suggest they may harbour similar driving mutations. In this study, aimed at characterizing the mutational status of SMO, BRAF, HRAS, KRAS, NRAS and FGFR2 in CAA, we used RNA sequencing, Sanger sequencing and restriction fragment length polymorphism assays to demonstrate that 94% of CAA (n = 16) harbour a somatic HRAS p.Q61R mutation. The similarities in MAPK-activating mutational profiles between CAA and AM implicate conserved molecular mechanisms of tumorigenesis, thus, qualifying the dog as a potentially useful model of disease. Given the relevance of RAS mutations in the pathogenesis of odontogenic tumours and other types of cancer, the results of this study are of comparative, translational, and veterinary value.