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The rostral cranial fossa (RCF) consists of the sphenoid and ethmoid bones, which accommodate the olfactory bulbs and nerves along the recesses of the cribriform plate. Neoplasms located in the vicinities of the RCF can compress and/or invade the cribriform plate. Here we describe the clinical and pathologic findings of neoplasms involving the cribriform plate in 32 dogs and 17 cats autopsied over a 13-y period. The average ages of affected dogs and cats were 9.2 y and 9.7 y, respectively. No sex or breed predisposition was evident in dogs, but 13 of 18 cats were spayed females and 14 of 18 were domestic shorthair cats. The main clinical signs were seizures (10 cases) and epistaxis (5 cases) in dogs, and red-to-brown nasal discharge (5 cases) and seizures (4 cases) in cats. In dogs, the 22 sinonasal neoplasms included adenocarcinoma (14 cases), transitional carcinoma (4), squamous cell carcinoma (2), lymphoma (1), and histiocytic sarcoma (1); the 10 intracranial neoplasms consisted of high-grade gliomas (3 cases), psammomatous meningiomas (2), histiocytic sarcomas (2), olfactory neuroblastomas (2), and a meningeal granular cell tumor (1). In cats, the 14 sinonasal neoplasms included lymphoma (8 cases), adenocarcinoma (4), adenosquamous carcinoma (1), and squamous cell carcinoma (1); the 3 intracranial neoplasms consisted of oligodendroglioma (1), transitional meningioma (1), and olfactory neuroblastoma (1). [ABSTRACT FROM AUTHOR]

Synovial myxoma, a rare joint tumor in dogs, has traditionally been considered benign, acknowledging that local invasion into regional tissues including bone may be present. Given the diagnostic challenges in distinguishing synovial myxoma from other joint lesions through clinical features and diagnostic imaging, definitive diagnosis relies on characteristic gross and histologic features. Within the inner surface of the joint capsule, synovial myxomas form nodules of stellate-to-spindle cells within abundant myxomatous matrix. We present here 2 cases of synovial myxoma with metastasis to regional lymph nodes and compare these 2 cases to 3 cases without evidence of lymph node metastasis. Aside from lymphovascular invasion in one case with metastasis, there were no overt histologic features of the primary tumor to suggest aggressive biologic behavior. The finding of lymph node metastasis warrants reconsideration of the term "synovial myxoma" for this neoplasm. We suggest the term "synovial myxosarcoma," considering that histologic features of the primary tumor do not predict biologic behavior. Our case series highlights the importance of lymph node sampling in suspected synovial myxosarcoma cases as well as thorough histologic examination, emphasizing careful evaluation for lymphovascular invasion. [ABSTRACT FROM AUTHOR]

Objective: To report a case of delayed death after initial successful treatment of severe bromethalin intoxication in a cat. Case Summary: A 2‐year‐old neutered male domestic shorthair cat presented as a referral for bromethalin toxicosis and progressive neurological decline. At the time of referral, the cat was nonambulatory tetraparetic with minimal motor function in all 4 limbs and exhibited a dull mentation. Within the first 4 hours of hospitalization, the cat's neurological status continued to rapidly decline, and osmotherapy, corticosteroids, and intralipids were administered. The treatment regimen also included levetiracetam, thiamine, cholestyramine, vitamin E, and gingko biloba. Six days after bromethalin ingestion, the cat displayed marked neurological improvement with near normal mentation and mild tetraparesis and was discharged. The cat continued to do well at home with improving neurological status and function. Nine days after discharge, the cat was presented dead on arrival. Postmortem examination revealed transforaminal brain herniation secondary to spongy degeneration of the white matter and increased intracranial pressure as the cause of death. New Information Provided: To the authors' knowledge, this is the first report of a cat that suffered delayed death despite initial neurological improvement after being treated for severe bromethalin toxicosis. [ABSTRACT FROM AUTHOR]

Increased proliferation is a driver of tumorigenesis, and quantification of mitotic activity is a standard task for prognostication. This systematic review is an analysis of all available references on mitotic activity in feline tumors to provide an overview of the assessment methods and prognostic value. A systematic literature search in PubMed and Scopus and a nonsystematic search in Google Scholar were conducted. All articles on feline tumors that correlated mitotic activity with patient outcome were identified. Data analysis revealed that of the 42 eligible articles, mitotic count (MC, mitotic figures/tumor area) was evaluated in 39 studies, and mitotic index (MI, mitotic figures/tumor cells) in 3 studies. The risk of bias was considered high for most studies (26/42, 62%) based on small study populations, insufficient details of the MC/MI methods, and lack of statistical measures for diagnostic accuracy or effect on outcome. The MC/MI methods varied between studies. A significant association of MC with survival was determined in 20 of 28 (71%) studies (10 studies evaluated other outcome metrics or provided individual patient data), while 1 study found an inverse effect. Three tumor types had at least 4 studies, and a prognostic association with survival was found in 5 of 6 studies on mast cell tumors, 5 of 5 on mammary tumors, and 3 of 4 on soft-tissue sarcomas. MI was shown to correlate with survival for mammary tumors by 2 research groups; however, comparisons to MC were not conducted. Further studies with standardized mitotic activity methods and appropriate statistical analysis for discriminant ability of patient outcome are needed to infer the prognostic value of MC and MI. [ABSTRACT FROM AUTHOR]

One of the most relevant prognostic indices for tumors is cellular proliferation, which is most commonly measured by the mitotic activity in routine tumor sections. The goal of this systematic review was to analyze the methods and prognostic relevance of histologically measuring mitotic activity that have been reported for canine tumors in the literature. A total of 137 articles that correlated the mitotic activity in canine tumors with patient outcome were identified through a systematic (PubMed and Scopus) and nonsystematic (Google Scholar) literature search and eligibility screening process. Mitotic activity methods encompassed the mitotic count (MC, number of mitotic figures per tumor area) in 126 studies, presumably the MC (method not specified) in 6 studies, and the mitotic index (MI, number of mitotic figures per number of tumor cells) in 5 studies. A particularly high risk of bias was identified based on the available details of the MC methods and statistical analyses, which often did not quantify the prognostic discriminative ability of the MC and only reported P values. A significant association of the MC with survival was found in 72 of 109 (66%) studies. However, survival was evaluated by at least 3 studies in only 7 tumor types/groups, of which a prognostic relevance is apparent for mast cell tumors of the skin, cutaneous melanoma, and soft tissue tumor of the skin and subcutis. None of the studies using the MI found a prognostic relevance. This review highlights the need for more studies with standardized methods and appropriate analysis of the discriminative ability to prove the prognostic value of the MC and MI in various tumor types. Future studies are needed to evaluate the influence of the performance of individual pathologists on the appropriateness of prognostic thresholds and investigate methods to improve interobserver reproducibility. [ABSTRACT FROM AUTHOR]

Background: Shortening of the colon has been described in cats, but its imaging and clinicopathological features remain poorly understood. Objectives: Description of the signalment, clinical presentation, imaging, endoscopic and histological features of short colon syndrome in cats. Animals: Ninety‐three cats diagnosed with short colon. Methods: Multi‐institutional, descriptive, retrospective case series study. Medical records were searched for a diagnosis of short colon on abdominal ultrasonography, computed tomography, endoscopy, autopsy, or a combination of these modalities. Results: The median age of included cats was 12 years at the time of diagnosis. Diarrhea was the most common clinical sign (60/92; 65%), followed by vomiting (36/92; 39%), weight loss (36/92; 39%), and inappetence (24/92; 26%). Thirteen percent of cats (12/92) had no signs of gastrointestinal disease at the time of diagnosis. In addition to a shortened colonic length, 79% (66/84) of cats had concomitant colonic thickening on ultrasonographic examination. On colonoscopy, mucosal ulcerations of the colonic wall were seen in 39% (9/23) of cats. Histopathologically, all cats but 1 (diagnosed simultaneously with colonic small cell lymphoma) had lymphoplasmacytic colitis, and when small intestinal biopsies were performed, concurrent lymphoplasmacytic enteritis or small cell lymphoma of the small intestine. Conclusions and Clinical Importance: Lymphoplasmacytic colitis is seen commonly in cats with short colon, suggesting a potential link between these entities. [ABSTRACT FROM AUTHOR]

Simple Summary: We investigated a new method for diagnosing and predicting outcomes in canine pulmonary carcinoma. We developed a deep learning-based algorithm that accurately detects tumor nuclei and subsequently measures size and shape parameters. The variation in nuclear size and shape (nuclear pleomorphism) is a crucial malignancy criterion used in the current grading system for canine pulmonary carcinoma. Pathologists currently evaluate it and classify it according to a three-tier system. Manual morphometry is a more objective approach where tumor nuclei are individually encircled and analyzed. This task can be easily performed by an algorithm. Our algorithm's accuracy in correctly detecting and segmenting tumor nuclei was considered good when compared to manual morphometry. By comparing automated morphometry with conventional prognostic tests, such as pathologists' estimates, mitotic count, histological grading, and clinical staging, we found that our approach was equally accurate in terms of prognostic value. The algorithm's advantage lies in its high reproducibility and efficiency. Automated evaluation of nuclear pleomorphism can enhance the efficiency and reliability of canine pulmonary carcinoma diagnosis and grading, effectively addressing issues of inter-observer reproducibility. However, further optimization of the algorithm and validation with a larger study group is necessary to confirm our findings. The integration of deep learning-based tools into diagnostic workflows is increasingly prevalent due to their efficiency and reproducibility in various settings. We investigated the utility of automated nuclear morphometry for assessing nuclear pleomorphism (NP), a criterion of malignancy in the current grading system in canine pulmonary carcinoma (cPC), and its prognostic implications. We developed a deep learning-based algorithm for evaluating NP (variation in size, i.e., anisokaryosis and/or shape) using a segmentation model. Its performance was evaluated on 46 cPC cases with comprehensive follow-up data regarding its accuracy in nuclear segmentation and its prognostic ability. Its assessment of NP was compared to manual morphometry and established prognostic tests (pathologists' NP estimates (n = 11), mitotic count, histological grading, and TNM-stage). The standard deviation (SD) of the nuclear area, indicative of anisokaryosis, exhibited good discriminatory ability for tumor-specific survival, with an area under the curve (AUC) of 0.80 and a hazard ratio (HR) of 3.38. The algorithm achieved values comparable to manual morphometry. In contrast, the pathologists' estimates of anisokaryosis resulted in HR values ranging from 0.86 to 34.8, with slight inter-observer reproducibility (k = 0.204). Other conventional tests had no significant prognostic value in our study cohort. Fully automated morphometry promises a time-efficient and reproducible assessment of NP with a high prognostic value. Further refinement of the algorithm, particularly to address undersegmentation, and application to a larger study population are required. [ABSTRACT FROM AUTHOR]

Leptomeningeal gliomatosis (LG) is characterized by extensive dissemination of neoplastic glial cells in the subarachnoid space either without an intraparenchymal glioma (primary LG or PLG) or secondary to an intraparenchymal glioma (secondary LG or SLG). Given the low frequency of LG in human and veterinary medicine, specific diagnostic criteria are lacking. Here, we describe 14 cases of canine LG that were retrospectively identified from 6 academic institutions. The mean age of affected dogs was 7.3 years and over 90% of patients were brachycephalic. Clinical signs were variable and progressive. Relevant magnetic resonance image findings in 7/14 dogs included meningeal enhancement of affected areas and/or intraparenchymal masses. All affected dogs were euthanized because of the poor prognosis. Gross changes were reported in 12/14 cases and consisted mainly of gelatinous leptomeningeal thickening in the brain (6/12 cases) or spinal cord (2/12 cases) and 1 or multiple, gelatinous, gray to red intraparenchymal masses in the brain (6/12 cases). Histologically, all leptomeningeal neoplasms and intraparenchymal gliomas were morphologically consistent with oligodendrogliomas. Widespread nuclear immunolabeling for OLIG2 was observed in all neoplasms. The absence of an intraparenchymal glioma was consistent with PLG in 3 cases. The remaining 11 cases were diagnosed as SLG. [ABSTRACT FROM AUTHOR]

Simple Summary: The aim of this study was to evaluate a new microscopic parameter (atypical mitotic figures) in canine cutaneous mast cell tumors regarding the ability to predict patient survival (prognosis). Mast cell tumors are one of the most common skin tumors in dogs. Counting the number of tumor cells undergoing division (mitotic figures) is of prognostic importance for this tumor type. While normal cells have a highly regulated cell division (normal mitotic figures), tumor cells might exhibit errors during chromosome separation into daughter cells. These errors can be identified microscopically as atypical mitotic figures and are described as a malignancy criterion for some human tumors. In this study, we have shown that a high number of atypical mitotic figures in canine cutaneous mast cell tumors is predictive of shorter patient survival. As compared to enumerating all mitotic figures, increased numbers of atypical mitotic figures (≥3 per 2.37 mm2) had a higher specificity for tumor-related death. These findings should be validated in future studies. Cell division through mitosis (microscopically visible as mitotic figures, MFs) is a highly regulated process. However, neoplastic cells may exhibit errors in chromosome segregation (microscopically visible as atypical mitotic figures, AMFs) resulting in aberrant chromosome structures. AMFs have been shown to be of prognostic relevance for some neoplasms in humans but not in animals. In this study, the prognostic relevance of AMFs was evaluated for canine cutaneous mast cell tumors (ccMCT). Histological examination was conducted by one pathologist in whole slide images of 96 cases of ccMCT with a known survival time. Tumor-related death occurred in 11/18 high-grade and 2/78 low-grade cases (2011 two-tier system). The area under the curve (AUC) was 0.859 for the AMF count and 0.880 for the AMF to MF ratio with regard to tumor-related mortality. In comparison, the AUC for the mitotic count was 0.885. Based on our data, a prognostically meaningful threshold of ≥3 per 2.37 mm2 for the AMF count (sensitivity: 76.9%, specificity: 98.8%) and >7.5% for the AMF:MF ratio (sensitivity: 76.9%, specificity: 100%) is suggested. While the mitotic count of ≥ 6 resulted in six false positive cases, these could be eliminated when combined with the AMF to MF ratio. In conclusion, the results of this study suggests that AMF enumeration is a prognostically valuable test, particularly due to its high specificity with regard to tumor-related mortality. Additional validation and reproducibility studies are needed to further evaluate AMFs as a prognostic criterion for ccMCT and other tumor types. [ABSTRACT FROM AUTHOR]