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Topic:Histology
Histology in horses involves the microscopic examination of tissues to understand their structure and function. This field of study provides insights into the cellular composition and architecture of equine tissues, aiding in the diagnosis of diseases and the assessment of tissue health. Histological analysis is used to identify pathological changes, such as inflammation, neoplasia, or degenerative conditions, by examining tissue samples obtained through biopsies or necropsies. Common tissues studied in equine histology include skin, muscle, bone, and internal organs. This page compiles peer-reviewed research studies and scholarly articles that explore histological techniques, findings, and their applications in equine veterinary medicine.
Association Between Matrix Metalloproteinase-9 (MMP-9) Immunohistochemical Expression and Clinicopathological Features in Equine Melanoma. Equine melanoma is one of the most important oncological diseases in horses and exhibits a distinct biological behavior compared with melanoma in other species. Matrix metalloproteinase-9 (MMP-9) has been associated with tumor aggressiveness and metastasis in human and canine melanoma, but its expression in equine melanoma remains unknown. Objective: Evaluate the immunohistochemical expression of MMP-9 in equine melanomas and investigate its association with clinicopathological features. Methods: 68 formalin-fixed, paraffin-embedded equine melanomas from 48 gray horses were evaluated immunohis...
[Cutaneous vascular hamartoma in a foal]. Vascular hamartomas are rare malformations in foals that typically present as painless masses of the skin or subcutaneous tissue. This case report describes a newborn foal with a vascular mass over the right shoulder. Complete surgical excision was performed at seven days of age. Histologically, the lesion was found to be a well-defined dermal vascular proliferation consistent with a vascular hamartoma. The healing process was uneventful, and no recurrence occurred six months postoperatively. This case adds a rare location on the scapula to the literature and confirms surgical removal as an ef...
Histological differences in the placenta of three mares treated for ascending bacterial placentitis compared to physiological pregnancies. Ascending bacterial placentitis is a frequent cause of late pregnancy loss in mares. The histology of placentitis has been described but mainly with a focus on inflammatory changes. In this study, we assessed several aspects beyond inflammatory processes between mares foaling close to term during treatment for placentitis and physiological pregnancies. We included placental tissue from physiological term pregnancies (group PP; n = 8) and clinical cases with confirmed ascending bacterial placentitis (group PL; n = 3). Samples were collected from several locations of the allantochorion (cerv...
Multi-Detector Helical Computer Tomography, Transrectal Ultrasonography and Histology of the Lumbosacral Area: A Comparative Study in Warmblood Horse Cadavers. Pain arising from the lumbosacral region is a recognized cause of poor performance and impaired welfare in horses. However, structural changes in the intertransverse joints (ITJs), lumbar articular process joints (APJs), and lumbosacral intervertebral discs (LSDs) may also occur in asymptomatic horses, complicating interpretation of imaging findings.This study evaluated these structures in 14 middle-aged Warmblood cadavers that were not lame according to the owners prior the onset of the problem that resulted in euthanasia or slaughter and correlated ultrasonographic (US) and computed tomograp...
Ostium-specific equine pulmonary vein myocardial sleeve gross anatomy and structural evidence of interatrial myocardial continuity with potential implications for ablation strategies. Pulmonary vein (PV) myocardial sleeves (MSs) harbour an arrhythmogenic substrate for atrial fibrillation. However, equine-specific data on MS distribution and wall thickness are limited yet essential for developing ablation strategies. In humans, posterior interatrial connections can compromise right-sided PV isolation. Objective: To study equine PV MS distribution, quantify ostial/branch diameters, antral lengths, characterise MS distal edge morphology, measure wall thickness and explore an interatrial myocardial continuity between the MSs of caudal branches draining through ostium III (PV II...
Histomorphometric and Histochemical Changes in the Mare Tuba Uterina During the Oestrous Cycle and Follicular Cyst Condition. This study evaluated histomorphometric and histochemical changes in the mare tuba uterina during different reproductive stages and under follicular cyst conditions. Forty nonpregnant mares were classified into follicular, luteal, post-ovulation and follicular cyst groups (n = 10/group). Histological evaluation of the isthmus, ampulla and infundibulum was performed using haematoxylin and eosin staining, while periodic acid-Schiff (PAS) staining was used to assess epithelial secretory activity. Morphometric parameters included number of primary mucosal folds, fold length, epithelial height a...
Leptomeningeal dissemination of a poorly differentiated carcinoma involving the trigeminal ganglion in a horse: a case report. Neoplastic conditions involving cranial nerves are uncommon in horses and represent a significant diagnostic challenge. Leptomeningeal dissemination is a recognized mechanism of tumor progression in aggressive neoplasms but is rarely reported in this species. A 15-year-old mixed-breed horse with a history of periocular squamous cell carcinoma treated by enucleation three years earlier developed progressive neurological signs. Initial differential diagnoses included metastatic neoplasia and equine protozoal myeloencephalitis. Due to rapid neurological deterioration, euthanasia and necropsy were...
Neosaxitoxin Downregulates Inflammation in an Equine In Vivo Model of Osteoarthritis. Chronic synovial inflammation is a hallmark of osteoarthritis progression and is tightly regulated by synovial macrophages. Recently, voltage-gated sodium channels (NaV) have emerged as potent modulators of macrophage-driven inflammation, positioning them as novel therapeutic targets. Among selective NaV channel blockers, neosaxitoxin exerts remarkable anesthetic and immunomodulatory effects; however, its effects on joint inflammation upon intra-articular delivery remain unexplored. Using an equine model of bilateral carpal osteoarthritis, this study evaluated the immunomodulatory and tissue-p...
Clinical outcomes of a novel flowable calcium silicate cement in equine endodontic treatment. Orthograde endodontic treatment of equine cheek teeth is performed infrequently with variable success rates of obturation with calcium hydroxide paste (CHP). A novel flowable calcium silicate cement (eCSC) formulated for use as an obturation material in equine teeth has demonstrated acceptable canal filling volumes and evidence of dentinal tubule penetration. However, clinical outcomes of eCSC-obturated equine teeth have not been reported. Objective: To report the clinical outcomes of orthograde endodontic treatment using eCSC. Methods: Retrospective case series. Methods: Horses that underwent...
Morphological and Biomechanical Characterization of Amniotic Membranes Across Species: Equine, Canine, Porcine, Ovine, and Human Samples-A Pilot Study. The use of amniotic membrane (AM) has become well established in the treatment of ocular surface disorders in both humans and animals. However, comparative studies of AM from different species remain scarce. Objective: To compare the thickness and biomechanical properties of equine, canine, porcine, and ovine AMs with those of human AM. Methods: Placentas were collected, and AMs were manually separated from the chorion. All AM samples were cryopreserved in a 1:1 solution of Dulbecco's Modified Eagle's Medium (DMEM) and glycerin at -80°C for 60 days. After thawing, samples underwent thicknes...
Oxidative Stress and Immunomarkers in Equine Dermal Melanomatosis: Single-Case Comparison with Healthy Individual. Dermal melanomatosis is a common tumor in grey horses, characterized by cutaneous/subcutaneous lesions with metastatic potential. While clinically well-described, oxidative stress involvement remains poorly understood. This case report compared oxidative stress markers and antioxidant enzymes' activities in total protein extracts from melanomatosis lesions (grey horse) versus healthy control skin (black horse), alongside histopathology and immunohistochemistry, to correlate oxidative imbalance and tumor behavior. Melanomatosis tissue exhibited decreased antioxidant defenses confirmed by catala...
The Transcriptomic and Proteomic Molecular Signatures of Equine Multiple-System Neuropathy (Grass Sickness). Equine grass sickness (EGS or equine dysautonomia) is a predominantly fatal multi-system neuropathy affecting grazing horses, likely caused by a neurotoxic phospholipase A2 (nPLA2) derived from a plant or microorganism. We studied neuronal tissue gene and protein expression patterns in EGS to elucidate the possible mechanisms of neurotoxicity and neurodegeneration. Tissue from the cranial cervical ganglion of eight EGS horses and six controls was examined histologically and used for transcriptomic analysis. These transcriptomic data were compared with previously published EGS-related proteomic...
Morphological investigation of myocardial sleeves with potential relevance to atrial fibrillation in Norwegian-Swedish Coldblooded Trotters. Myocardial sleeves (MSs) are thin layers of cardiac muscle that extend from the atria into the caval and pulmonary veins. They are recognised as important structures in both initiating and maintaining atrial tachycardia, and especially atrial fibrillation (AF), which is the most clinically important cardiac arrhythmia in horses with a reported prevalence of 1.3-2% in Standardbred racehorses. In contrast, the Norwegian-Swedish Coldblooded Trotter (NSCT) has a much lower prevalence of AF despite experiencing similar physical demands. The purpose of this study was to describe the macro-, and micr...
Mammary neuroendocrine tumor in a mare. A 10-y-old American Paint Horse mare was presented to the Equine Field Services at Virginia-Maryland College of Veterinary Medicine (Blacksburg, VA, USA) for evaluation of mastitis and a possible abscess in the right mamma. Histologic evaluation of a mammary biopsy revealed a densely cellular, infiltrative neoplasm with cells arranged in packets supported by thin stroma. In a neuroendocrine immunohistochemistry panel, the neoplastic cells did not immunolabel for neuron-specific enolase or synaptophysin, positively immunolabeled for chromogranin A, and had moderate scattered immunolabeling for ...
Morphological study of nasal diverticulum in Grant’s zebra (Equus quagga boehmi Matschie, 1892). The nasal diverticulum (ND), a blind cutaneous pouch extending from the nasal vestibule (NV), is unique to Equidae. Although anatomical and histological descriptions of the ND are available for horses and donkeys, detailed studies in zebras remain limited. Objective: To investigate and characterize the anatomical and histological features of the ND in zebras and compare these findings with those observed in other species. Methods: Silicone casts of the NDs were prepared from two of three female Grant's zebra carcasses for anatomical measurements, followed by dissection for gross morphological ...
Intra-articular interleukin-1β induces early synovitis in an ex vivo autologously perfused equine forelimb model. To evaluate an ex vivo model of synovitis induced by IA lipopolysaccharide (LPS) and IL-1β in isolated, perfused equine forelimbs. Unassigned: Forelimbs and blood were collected from 12 clinically unremarkable horses following slaughter at a licensed abattoir. In 8 limbs, 2 of 3 phalangeal joints were injected with LPS (0.5 to 5 ng, 4 limbs) or IL-1β (100 ng, 4 limbs) diluted in 1 mL of distilled water. All limbs were perfused with autologous perfusate for 8 hours. Synovial fluid cytology and synovium sample histology scores for synovitis (0 = no changes and 3 = marked changes) were assessed...
Exploring the role of epigenetics in the processes related to the development of endometrosis in the mare. Endometrosis is a chronic degenerative condition of the mare endometrium characterized by progressive fibrosis and glandular alterations that impair uterine function and fertility. Its pathogenesis involves persistent inflammation, the activation of myofibroblasts, and the accumulation of extracellular matrix (ECM), leading to disrupted glandular secretion and compromised maintenance of pregnancy. While histopathological studies of endometrosis are well described, the underlying molecular mechanisms remain incompletely understood. Emerging evidence highlights the crucial role of epigenetic reg...
Gross and Histopathologic Comparison of the Distal Third Metacarpal Bone and the Proximal First Phalanx with Sodium Fluoride Positron Emission Tomography Radiopharmaceutical Uptake in Five Horses. Injuries of the metacarpophalangeal joint are a major cause of morbidity and catastrophic fracture in racing horses, yet early osseous pathology is often difficult to detect using conventional imaging. This pilot study aimed to correlate sodium fluoride Positron Emission Tomography (F-NaF PET) radiopharmaceutical uptake with gross and histopathologic changes in the distal third metacarpal bone (MC3) and proximal first phalanx (P1). Five horses (three racing Thoroughbreds with fetlock injury and two non-racing controls) underwent ante-mortem F-NaF PET and cone-beam CT imaging (CBCT), followed b...
Transcriptomic and Meat Quality Differences in Longissimus Dorsi Muscle of Surgically Castrated Three-Year-Old Kazakh Horses. Although the Kazakh horse is a dual-purpose breed renowned for both milk and meat production, the extent to which surgical castration alters gene expression in its muscles has not yet been fully elucidated. In this study, left longissimus dorsi muscle (LDM) samples were obtained from six Kazakh stallions (W group) and six Kazakh geldings (S group) to comparatively evaluate meat quality parameters, examine histological characteristics in tissue sections, and apply transcriptomic profiling to comprehensively explore the principal regulatory pathways and candidate genes through which surgical cas...
Vital bone and increased osteoid in equine osteochondrosis dissecans of the proximal phalanx: A controlled study indicating a mineralization deficit rather than vascular failure. Osteochondrosis and osteochondrosis dissecans (OCD) are among the most common orthopaedic disorders in young horses. Although traditionally explained by vascular failure and ischaemic necrosis, recent findings in human juvenile OCD suggest that impaired bone mineralization may play an important role. Horses are known to have relatively low circulating vitamin D metabolites, raising the question of whether insufficient mineralization contributes to equine OCD. This study investigated the bone vitality and mineralization status of osteochondrosis dissecans fragments (OCDFs) collected from the do...
An unusual presentation of a sarcoid in Australia. Sarcoids are a common skin tumour affecting all equids. To date, only one case of a sarcoid in the oral cavity of the horse has been reported. In the present case, an oral sarcoid was identified using histology and polymerase chain reaction to detect bovine papillomavirus type 2 DNA. The lesion was known to be incompletely surgically excised and did not recur over a 15-month period. This case report describes the first oral sarcoid identified in Australia.
Comparative cardiac histopathology and toxicology screens in horses succumbing to exercise-associated sudden cardiac death and control horses. Horse racing has faced increased scrutiny because of concerns about equine welfare and the safety of both equine and human participants. Sudden death (SD) in racehorses is relatively uncommon, and its causes are still unclear. Little information and considerable confusion exist regarding the clinical significance of microscopic lesions in the hearts of horses with SD. We examined the hearts of 29 horses that suffered exercise-associated sudden cardiac death (EASCD) and 29 clinically healthy control horses that were euthanized because of catastrophic musculoskeletal injuries. Acute cardiomyocyt...
Equine Liver Histopathology. This review summarizes best practices for equine liver biopsy, including when to perform a biopsy, techniques for sample collection and handling, and strategies to optimize diagnostic yield. It discusses the interpretive framework used by pathologists, common diagnostic challenges, and prognostic scoring systems. Limitations such as sampling error and variability among observers are considered alongside ancillary testing, immunohistochemistry, and in situ hybridization. Emphasis is placed on the importance of communication between clinicians and pathologists to maximize diagnostic and prognost...
Verminous mastitis caused by Cephalobus cubaensis infection in a mare. A 7-y-old American Quarter Horse mare was presented to a veterinary hospital for ongoing reproductive monitoring and management of endometritis. During physical evaluation, several nodular lesions of unknown origin and duration were discovered in the mammae. Histologically, biopsies from the lesions were confirmed as severe granulomatous mastitis with intralesional rhabditid nematodes. A putative diagnosis of or infection was assigned, and ivermectin (1.2 mg/kg PO) treatment was given every 2 wk. When lesions persisted after the initial dose of ivermectin, PCR testing of and gene targe...
Macroscale and microscale mechanical and biochemical properties of the equine superficial digital flexor tendon are regionally dependent. To examine regional mechanical and biochemical differences across the length of the equine superficial digital flexor tendon (SDFT). Unassigned: Equine SDFTs were collected postmortem from 9 donors and divided into proximal, middle, and distal regions based on the location of the musculotendinous and osteotendinous junctions. Tensile testing was performed on samples to obtain macroscale mechanical properties, and atomic force microscopy was done to obtain microscale mechanical properties. Biochemical assays and histological staining were done to assess glycosaminoglycan (GAG), collagen, and DN...
Structural Features of the Equine Small Intestinal Mesenteric Attachment Predisposing to Rupture. Rupture of equine small intestine with formation of a pouch of ingesta within the mesentery has been reported in clinical colic cases. Multiple ex-vivo studies using anastomosed jejunum observed rupture into the mesentery, distant to the anastomosis. Both scenarios suggest the jejunum is predisposed to rupture at the mesenteric attachment. The aim of the study is to 1) document the location at which equine jejunal segments rupture when subjected to high intraluminal pressures, 2) identify predisposing anatomical features that may confer weakness at the point of rupture and 3) demonstrate jejun...
A novel flowable calcium silicate cement for endodontic therapy in equine teeth. Equine endodontic treatment for apical infections is performed infrequently due to anatomical and accessibility challenges of equine cheek teeth. However, the alternative of extraction is not without risk and lifelong implications for the horse. Mineral trioxide aggregate (MTA), a calcium silicate cement (CSC), has been used successfully in human dentistry for decades. MTA and other CSCs demonstrate excellent biocompatibility with favourable antimicrobial and physicochemical properties. These characteristics may support their application as an alternative filling material when used in equine e...
Unusual, fatal neck cancer in a foal: immunohistological investigations and differential diagnosis. Neck masses may represent a diagnostic challenge for equine veterinarians, since they may involve different structures with a similar clinical appearance. Whereas neck masses in foals mostly result from non-neoplastic conditions, including various congenital abnormalities, neoplastic cervical masses have been rarely documented. This report describes the unusual case of a rapidly growing neck cancer in a four-month-old colt, resulting in a fatal outcome. Gross and immunohistological findings were most consistent with a poorly differentiated thymic carcinoma with sarcomatoid features and multifo...
Rostral hard palate swelling (lampas) in horses: true or fiction? This study aimed to determine the occurrence of swellings (lampas) in the rostral portion of the hard palate in young, adult, and elderly horses and to characterize them histologically. One hundred and twenty horses of different ages were evaluated by oral inspection. Horses were classified with lampas when the mucosa of the hard palate extended beyond the occlusal surface of the upper incisors and samples of palatal mucosa were collected. Ten other horses without rostral hard palate alterations, euthanized for unrelated causes, were included as the control group. Histological analysis include...
Piezosurgical partial ostectomy of the incisive bone for an ossifying fibroma removal in a 4-year-old Warmblood gelding. Ossifying fibromas are uncommon in horses and complete surgical excision with premaxillectomy, maxillectomy or mandibulectomy is recommended. Piezosurgery has been previously used in equines only in one study. Objective: To report a case of ossifying fibroma treated with piezosurgery and to describe its follow-up. Methods: Clinical case report. Methods: A 4-year-old Zangersheide gelding was presented for a mass occupying the space of tooth 202. Histology confirmed the diagnosis of ossifying fibroma, which was removed by resection of soft tissues and a slice of the premaxilla with a piezotome. ...
