Tumors in horses are abnormal growths of tissue that result from uncontrolled cell division. They can be benign or malignant and may affect various tissues and organs within the equine body. Common types of tumors in horses include sarcoids, melanomas, and squamous cell carcinomas. The presence and progression of tumors can impact a horse's health, performance, and quality of life. Diagnosis often involves clinical examination, imaging techniques, and histopathological analysis. This page compiles peer-reviewed research studies and scholarly articles that explore the types, diagnosis, treatment options, and prognostic factors associated with tumors in equine medicine.
Sundberg JP, Burnstein T, Page EH, Kirkham WW, Robinson FR.In a retrospective study of neoplasms in Equidae pre;ented to the Animal Disease Diagnostic Laboratory, Purdue University, from Jan 1, 1970, to Dec 31, 1974, data were compiled on numbers and anatomic sites of neoplasms as well as on age, sex, and breed of subjects from which the neoplasms were taken. During this 5-year period, 21 neoplasms were diagnosed from 687 equine necropsies (3.1%) and 215 from 635 biopsies (33.9%), totaling 236 neoplasms from 1,322 cases (17.9%). The most common neoplasms were sarcoids (43.6%) and squamous cell carcinomas (24.6%). Papillomas (5.5%), nerve sheath tumors...
Cotchin E.Published figures from veterinary schools indicate that tumours may account for about 1 to 3 per cent of surgical cases. In this paper an account is given of clinical and pathological aspects of the tumours that are most likely to be encountered in practice, either as visibly or palpably detectable masses of tissue, or as internal tumours responsible for clinical signs. Amongst the common and important tumours dealt with, the most prominent are "equine sarcoid", squamous-cell carcinoma (of eye region and of glans penis), granulosa-cell tumours and melanomas. Well over a hundred references prov...
Moore JN, Kintner LD.Squamous cell carcinoma involving the pars esophagea of the stomach caused recurrent esophageal obstruction in an 11 year old Pinto gelding. The tumor encircled the esophagus and was attached to the diaphragm, spleen, aorta, left adrenal gland and kidney. Definitive diagnosis was provided by biopsy of the mass via standing left flank laparotomy.
Hall WC, Nielsen SW, McEntee K.Tumours of the male genital tract, excluding the testes, are relatively rare in the six major domestic animals. The most important tumours are prostate carcinoma and transmissible venereal tumour of the penis in dogs, fibropapilloma of the penis in bulls, squamous papilloma and squamous cell carcinoma in horses, and squamous papilloma in pigs. Four histological types of canine prostate carcinoma exist: alveolar papillary, acinar, organoid, and poorly differentiated. The biological behaviour of prostate carcinomas is similar to that in man, with frequent metastasis to the regional pelvic nodes,...
Kenney RM, Ganjam VK.Focal enlargements of the uterus are palpable through the rectal wall and have various aetiology. Aspects of their diagnosis, possible pathogenesis, significance and treatment are presented. Lymphatic lacunae appear to be quite common in older mares and may occasionally give rise to large endometrial cyst, but more frequently cause widespread change throughout the uterine horns. Three unusual ovarian abnormalities are presented, a large, oestrogen-producing granulosa cell tumour, an oestrogen-producing large follicle in a 4-month-old filly, and an ectopic progesterone-producing adrenal structu...
Stickle RL, Erb RE, Fessler JF, Runnels LJ.Unilateral ovariectomy was performed on 3 mares affected with granulosa cell tumors. Tumor fluid in each mare was found to contain estrogen, testosterone, and progesterone. In 2 mares, preoperative blood plasma concentrations of these hormones were comparable to those of a series of clinically normal mares. The other mare, which had a history of aggressive, masculine behavior, had higher testosterone content in the tumor fluid and in the preoperative blood sample. After surgical removal of the tumors, each mare developed follicles and ovulated with the remaining ovary. Each was eventually bred...
Baker JR, Leyland A.In a histological survey of 244 tumerous growths from 155 horses, the tumours commonly found were fibromas, squamous cell carcinomas, sarcoids and papillomas, most frequently affecting the skin, external genitalia, eye and orbit. The histological features that differentiate fibroblastic citaneous growths are detailed so that the clinical behaviour of these distinct neoplasms can be studied.
Mason BJ.A case of spindle cell sarcoma of the equine para-nasal sinuses is described and discussd in relation to similar tumours recorded in the literature.
Hayes HM, Priester WA, Pendergrass TW.From 11 North American veterinary university hospitals and clinics, 248 animals were a confirmed diagnosis of nervous-tissue tumor were identified; 7 tumors were found in cattle, 28 in horses, 14 in cats, 199 in dogs, and none in other species. Tumors were divided for analysis into three categories-glial, meningeal, and peripheral nerve. In cattle and horses, all tumors involved peripheral nerves, the risk of which, in horses, reached a plateau at 4-6 years of age and remained constant thereafter. In cats, the tumors were equally distributed among the three tumor categories whereas, in dogs, t...
Ford GH, Empson RN, Plopper CG, Brown PH.Masses removed from the superficial fascia of the jugular groove of a 12-year-old Arabian mare and from the femoral canal of a 7 1/2-year-old female cat appeared to be counterparts of the human malignant giant cell tumor of soft parts, even recapitulating the clinical behavior of the respective subgroups. Histologically, both neoplasms contained the characteristic features of the malignant giant cell tumor of soft parts: large multinucleate giant cells, pleomorphic mononuclear giant cells, histiocytes, fibroblasts and fibrocytes that were sometimes sarcomatous, and foci of hemorrhage and necro...
Ramadan RO.The clinical features and pathology of an ocular melanoma in a young born-grey mare are described. The tumour, possibly arising on the cornea, invaded the eye and extra-orbital muscles. Histologically; it consisted predominantly of spindle-shaped and polygonal cells containing melanin.
Watson RE, Larson KA.Indirect immunofluorescence and lymphocyte cytotoxicity experiments demonstrated the presence of a tumor-specific antigen(s) on the surface of cells from an equine sarcoid cell line (Mc1). Autologous serum (taken from the horse from which the Mc1 cells were derived) and sera from three other sarcoid-bearing horses revealed a similar membrane immunofluorescence when reacted with Mc1 cells, indicating the existence of cross-reacting antibodies. Results of serum colony inhibition experiments indicate that these antibodies are not cytotoxic. Incubation of Mc1 cells with autologous lymphocytes resu...
Watson RE, England JJ, Larson KA.A cell line, derived from a spontaneous equine connective tissue tumor (equine sarcoid), has been established. The morphological and growth characteristics indicative of malignant transformation of the cells include a disoriented, rapid growth and loss of contact inhibition. Further evidence of transformation is the agglutination of these cells by concanavalin A and their ability to divide in semisolid media.
Hutchins DR.This study examines a set of cases relating to tumoral calcinosis in horses. This condition, often found in larger dog breeds and humans, is marked by a calcareous, firm mass […]
Drozdzewska K, Gehlen H.The diagnosis of internal neoplasia in horses is challenging. Increased production of hormones physiologic for adult animals (e.g., adrenocorticotropin, norepinephrine, and erythropoietin) or typical for the foetal phase (alpha-fetoprotein, anti-Müllerian hormone, and parathyroid-hormone-related protein) might aid in tumour diagnostics. Thymidine kinase-1 and alkaline phosphatase are examples of intracellular enzymes, whose activity in the blood may increase in some neoplasia cases. Furthermore, inappropriate production of abnormal monoclonal or autologous antibodies can accompany lymphoma an...
Miyazawa T.Diseases caused by animal retroviruses have been recognized since 19th century in veterinary field. Most livestock and companion animals have own retroviruses. To disclose the receptors for these retroviruses will be useful for understanding retroviral pathogenesis, developments of anti-retroviral drugs and vectors for human and animal gene therapies. Of retroviruses in veterinary field, receptors for the following viruses have been identified; equine infectious anemia virus, feline immunodeficiency virus, feline leukemia virus subgroups A, B, C, and T, Jaagsiekte sheep retrovirus, enzootic na...
Mathes RL, Paige Carmichael K, Peroni J, Anthony Moore P.A 5-year-old Draft Horse gelding presented for evaluation of a large, fleshy, ulcerated third eyelid mass OD of 3 weeks duration. Complete ophthalmic examination, ocular ultrasound and skull radiographs revealed a large soft-tissue mass involving the entire third eyelid OD and extending into the ventral right orbit to the level of the globe equator. No other abnormalities were noted on physical or ophthalmic examination. Surgical removal via exenteration was performed 3 months after initial presentation. A lacrimal adenocarcinoma of the third eyelid was diagnosed based on histopathology. Concu...
McCalla TL, Moore CP, Collier LL.A 5-year-old Pony of America mare was referred for evaluation of inflamed upper and lower right eyelids. Squamous cell carcinoma of the eyelids and ulcerative keratitis secondary to self-trauma were diagnosed. Initial treatment of the eyelid neoplasia with 2 applications of cryotherapy failed to resolve the lesions, and immunotherapy with bacillus of Calmette-Guerin (BCG) was instituted. Multiple injections of BCG over a 17-week period resulted in progressive shrinkage of the tumor mass, but regional metastasis to the ipsilateral submandibular lymph node occurred. Six months later, ocular neop...
Zetterström SM, Matz BM, Neto RLALT, Lindley SES, Cole RC, Wilhite R, Boone LH.To describe the surgical findings, histopathological features, and long-term outcome for a horse with parotid salivary carcinoma. Methods: Case report ANIMALS: Twelve year old American Quarter Horse gelding. Methods: The gelding was presented for a 10 × 10 cm swelling below the base of the right ear. Ultrasonographic examination revealed a mass involving the right parotid salivary gland. Incisional biopsy was consistent with parotid carcinoma. The tumor was marginally excised. The lateral wall of the guttural pouch was excised with the mass and was reconstructed with a porcine small int...
Silverstone AM, Tatarniuk DM, Durket E, Gillen AM.A 15-year-old Pony of America (POA) gelding presented for evaluation of a large mass present on the right external pinna. Based on gross appearance, the right ear mass was suspected to be neoplastic. The most likely differential diagnosis was that of a fibroblastic sarcoid. Complete auriculectomy via use of a constricting latex-tourniquet performed under multimodal analgesia was proposed as an option to achieve complete resolution of mass growth and improve patient comfort. Benefits of latex tourniquet constriction included immediate lack of bleeding associated with amputation, gradual ischemi...
Cavatorta P, Crippa PR, Ito AS, Casali E, Ferrari MB, Masotti L.In the present paper we report a comparative study of physical properties and biochemical composition of isolated melanosomal membranes extracted from bovine eyes and from an equine spleen melanoma. Some biophysical characteristics of such membranes were obtained by steady-state and time resolved fluorescence spectroscopy using DPH as fluorescent probe. By these methods we have measured both static fluorescence polarization and fluorescence lifetimes and from the experimental data we have calculated the rotational correlation times by Perrin's equation. Since dynamic and static parameters, suc...
Roels S, Tilmant K, Van Daele A, Van Marck E, Ducatelle R.Melanocytic tumours are a well-known clinical and pathological entity in horses, but further phenotypic characterization of these tumours is lacking. Six melanocytic tumours from five horses (two metastatic and four benign) were examined by Ki67, PCNA and p53 immunostaining, DNA nick end labelling (Tunel) and Feulgen staining. The stainings were evaluated using quantitative image analysis. The resulting parameters of growth fraction (Ki67), S-phase index (PCNA), p53 index, apoptotic index, DNA index, nuclear diameter, ploidy balance, proliferation index (Feulgen) and hyperploidy were analysed....
Nakayama H, Shiga T, Uchida K, Chambers JK, Morino T, Sasaki N.There is no nationwide necropsy database of animals in Japan, and most of the records are available from the postwar period. To clarify the chronological transition of animal necropsy cases in Tokyo, Japan, the records accumulated in The University of Tokyo from 1902 were investigated. Of necropsy records on paper or electronic from 1902 to 2021 kept at the Laboratory of Veterinary Pathology, The University of Tokyo, totally 3,137 cases including 572 in 1903-1914 (the Meiji-Taisho period), 1,258 in 1956-1969 (the Showa period) and 1,307 in 2006-2020 (the Heisei-Reiwa period), respectively, wer...
Rabinovsky ED, Yang TJ.A tumor antigen (TA) associated with murine leukemia-lymphoma L5178Y cells has been identified by the enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence (IIF) techniques. The antigen was present in both non-solubilized and 0.5% NP-40 solubilized membrane extracts. Rabbit anti-L5178Y lymphoma serum (RALS), extensively absorbed with normal mouse tissues, identified TA in extracts of L5178Y lymphoma and L5178Y leukemia cells grown in horse serum (L5178Y/HS), but not in extracts of L5178Y cells grown in fetal calf serum (L5178Y/FCS). Similarly, absorbed rabbit anti-L5178Y/HS...
Risselada M, Worth DB.Tumors of various sizes and locations can create a treatment dilemma in achieving adequate surgical margins when sufficient free tissue is not available for closure. Extravascular local adjunctive chemotherapy has been investigated clinically to aid in achieving local tumor control in animals with naturally occurring neoplastic disease. Local chemotherapy can be an alternative primary or a local adjunctive treatment. This is a summary of relevant findings of in vitro and in vivo studies on local chemotherapeutic delivery through carrier media, together with a summary of outcomes of clinical us...
Hajimohammadi A, Ghane M, Ghari Tehrani M, Paravar B, Mirzaei A, Razavi S, Nikzad M.Sixty-one horses were enrolled in this study and divided into 3 different groups according to their severity of colic (heart rate, oral mucous membrane color, and abdominal distention): a strangulating colic (SC) group (n=21), non-strangulating colic (NC) group (n=20), and control group (n=20) consisting of randomly selected normal horses without signs of colic. The serum concentrations of haptoglobin, tumor necrosis factor-α (TNFα), nitric oxide (NO), malondialdehyde (MDA), zinc, iron, and copper were evaluated in all horses. The average concentration of TNFα in the SC group was higher tha...
Tommasa SD, Roth SP, Triebe T, Brehm W, Lohmann KL, Stöckle SD.Granulosa cell tumors (GCTs) are the most common ovarian tumors in mares. The classical presentation of a GCT is a unilaterally enlarged ovary appearing as a multicystic honeycomb mass. In rare cases, GCTs cause hemoperitoneum as a result of the rapid growth of the tumor. The clinical diagnosis of GCT is usually based on history, rectal examination, ultrasonographic examination, and serum hormone analysis, and surgical removal of the affected ovary is the treatment of choice. The different surgical approaches are based on the dimension of the GCT. A 7-year-old mare was referred to the departme...
Armando F, Porcellato I, de Paolis L, Mecocci S, Passeri B, Ciurkiewicz M, Mechelli L, Grazia De Ciucis C, Pezzolato M, Fruscione F, Brachelente C....Vulvo-vaginal epithelial tumors are uncommon in mares, and data on the epithelial-to-mesenchymal transition (EMT) and the tumor-immune microenvironment (TIME) are still lacking. This is a study investigating the equus caballus papillomavirus type 2 (EcPV2) infection state as well as the EMT process and the tumor microenvironment in vulvo-vaginal preneoplastic/ benign (8/22) or malignant (14/22) epithelial lesions in mares. To do this, histopathological, immunohistochemical, transcriptomic, hybridization, and correlation analyses were carried out. Immunohistochemistry quantification showed tha...
Brown KA, Gregorio EN, Barot D, Usimaki A, Linardi RL, Missanelli JR, You Y, Robinson MA, Ortved KF.To determine the effects of a single dose of the NSAIDs phenylbutazone, firocoxib, flunixin meglumine, and ketoprofen on concentrations of growth factors and cytokines in autologous protein solution (APS) and platelet-rich plasma (PRP). Methods: 6 adult university-owned horses. Methods: For the first phase, 6 horses were randomized to receive ketoprofen (1,000 mg) or flunixin meglumine (500 mg) IV. Blood was obtained and processed for APS (Pro-Stride) and PRP (Restigen) before and 6 hours after administration of NSAIDs. Horses underwent a 2-week washout period, after which the protocol was rep...
Fesmire CC, Peal B, Ruff J, Moyer E, McParland TJ, Derks K, O'Neil E, Emke C, Johnson B, Ghosh S, Petrella RA, DeWitt MR, Prange T, Fogle C, Sano MB.Integrated time nanosecond pulse irreversible electroporation (INSPIRE) is a novel tumor ablation modality that employs high voltage, alternating polarity waveforms to induce cell death in a well-defined volume while sparing the underlying tissue. This study aimed to demonstrate the in vivo efficacy of INSPIRE against spontaneous melanoma in standing, awake horses. Unassigned: A custom applicator and a pulse generation system were utilized in a pilot study to treat horses presenting with spontaneous melanoma. INSPIRE treatments were administered to 32 tumors across 6 horses and an additional 1...
Martabano BB, Dow S, Chow L, Williams MMV, Mack MK, Bellone R, Wotman KL.To determine the safety and efficacy of perilesional human recombinant interferon alpha-2b (IFNα2b) for treatment of periocular squamous cell carcinoma (PSCC) in horses. Methods: Eleven horses (12 eyes) with PSCC were enrolled in this prospective clinical study with owner consent. Methods: Systemically healthy horses were included in the study following confirmation of PSCC via biopsy. Every two weeks for a maximum of six treatments, horses were sedated and perilesional injection of IFNα2b (10 million IU) was performed. Tumors were measured prior to each injection and at one, three, and 12 m...
Gao Y, Packeiser EM, Wendt S, Sekora A, Cavalleri JV, Pratscher B, Alammar M, Hühns M, Brenig B, Junghanss C, Nolte I, Murua Escobar H.Malignant melanomas (MMs) are the abnormal proliferation of melanocytes and are one of the lethal skin cancers in humans, equines, and canines. Accordingly, MMs in companion animals can serve as naturally occurring animal models, completing conventional cancer models. The common constitutive activation of the MAPK and PI3K pathways in MMs has been described in all three species. Targeting the related pathways is considered a potential option in comparative oncologic approaches. Herein, we present a cross-species comparative analysis exposing a set of ten melanoma cell lines (one human, three e...
Hobbs KJ, Davis JL, Cooper BL, Ueda Y, Burke MJ, Sheats MK.Plasma cytokine adsorption has shown benefit as an adjunctive therapy in human sepsis but has yet to be investigated in horses. We hypothesized that ex vivo filtration of equine plasma with a novel cytokine adsorption device would significantly reduce concentrations of lipopolysaccharide-stimulated cytokines. We also hypothesized that the device would adsorb medications commonly used to treat sepsis. Methods: 8 horses owned by North Carolina State University. Methods: Four liters of heparinized whole blood was collected from healthy adult horses (n = 8) and stimulated with lipopolysaccharide (...
Barrantes Murillo DF, Cattley RC, Cullen JM, Withers C, Towns J, Pfeifle R, Wooldridge A, Neto RLALT.A 17-y-old Arabian mare was presented to the Auburn Large Animal Veterinary Teaching Hospital with a long-term history of intermittent mild recurrent colic that responded to medical treatment. CBC revealed mild lymphopenia; serum biochemistry findings were of increased gamma-glutamyl transferase and creatine kinase activities, hyperferremia, hyperglycemia, hypomagnesemia, and hypokalemia. Abdominocentesis was compatible with low-protein transudate. Due to the progression and duration of clinical signs, the owner elected euthanasia. Postmortem examination and histopathology confirmed a cholangi...
Singh SP, Besner GE, Schauer GM.This report describes the clinical and histologic features of a pulmonary tumor in a 14-year-old girl that is most consistent with a rare entity described in the literature as "pulmonary endodermal tumor resembling fetal lung" (PET). This tumor is composed of glycogen-rich columnar cells forming complex glands with focal festooning and mitotic activity, admixed with solid "morules" of cells with eosinophilic cytoplasm and focal nuclear clearing. Patchy tumor necrosis and a bland stroma were also present. Immunoreactivity for carcinoembryonic antigen (CEA), alpha 1-antichymotrypsin, and 12E7 wa...
Chow L, Flaherty E, Pezzanite L, Williams M, Dow S, Wotman K.Ocular surface squamous neoplasia (OSSN) represents the most common conjunctival tumor in horses and frequently results in vision loss and surgical removal of the affected globe. Multiple etiologic factors have been identified as contributing to OSSN progression, including solar radiation exposure, genetic mutations, and a lack of periocular pigmentation. Response to conventional treatments has been highly variable, though our recent work indicates that these tumors are highly responsive to local immunotherapy. In the present study, we extended our investigation of OSSN in horses to better und...
Pimenta J, Prada J, Pires I, Cotovio M.Equine melanomas are a common neoplasm in gray horses. However, scientific knowledge about their progression over time is quite scarce. Some owners and veterinarians still believe that early intervention is not necessary, stating that tumors evolve very slowly and intervention could worsen the animal's condition. This work aims to identify clinical and histological differences that may exist between equine melanomas with different excision intervals (time between tumor detection and surgical excision). A total of 42 tumors (13 benign and 29 malignant) from 34 horses were included in this study...
Blohm KO, Nell B.A 17-year-old Appaloosa mare was referred for evaluation of presumed refractory keratitis of the left eye. Gross examination revealed ocular discomfort and corneal neovascularization with a nasal focal opacification affecting approximately 40% of the corneal surface. On ophthalmic examination, extensive subepithelial to mid-stromal vascular branching accompanied by a homogeneous white, dense opacification, which affected up to 80% of the total corneal thickness, were apparent. Signs of concurrent uveitis were absent. Deep-stromal lamellar keratectomy with a conjunctival pedicle graft was perfo...
Pereira R, Gillespie S, Rapezzano G, Withers J, Duz M, Foote A.A 15-month-old, grey, Thoroughbred filly presented for investigation of a 6-week history of corneal oedema and blepharospasm on the right eye (OD). The filly was otherwise healthy. Following ophthalmic examination, glaucoma on the OD was diagnosed. A space occupying mass within the anterior chamber was documented on transpalpebral ultrasonographic examination. This mass obliterated most of the anterior intraocular structures on the peripheral nasal side (corneal endothelium and drainage angle), leading to secondary glaucoma. After systemic and topical treatment addressing secondary glaucoma, t...
Munday JS, Knight CG, Bodaan CJ, Codaccioni C, Hardcastle MR.Penile squamous cell carcinomas (SCCs) are common, potentially life-threatening neoplasms of horses. They are well-recognized to be caused by Equus caballus papillomavirus (EcPV) type 2, although EcPV2 cannot be detected in all cases. A 23-year-old standardbred gelding developed multiple penile in situ and invasive SCCs that contained histological evidence of PV infection. By using both consensus and specific PCR primers, these lesions were found to contain EcPV7 DNA, but not DNA from EcPV2 or any other PV type. To determine how frequently EcPV7 is present in equine penile SCCs, specific prime...
Brodesser DM, Kummer S, Eichberger JA, Schlangen K, Corteggio A, Borzacchiello G, Bertram CA, Brandt S, Pratscher B.The ability of human melanoma cells to switch from an epithelial to a mesenchymal phenotype contributes to the metastatic potential of disease. Metalloproteinases (MPs) are crucially involved in this process by promoting the detachment of tumor cells from the primary lesion and their migration to the vasculature. In gray horse melanoma, epithelial-mesenchymal transition (EMT) is poorly understood, prompting us to address MP expression in lesions versus intact skin by transcriptome analyses and the immunofluorescence staining (IF) of gray horse tumor tissue and primary melanoma cells. RNAseq re...
Lardone E, Landi A, Franci P.During electrochemotherapy (ECT), a chemotherapeutic drug is injected into the tumor and then an electroporation is provided. In horses, ear manipulation may be very painful, and combining a loco-regional technique with sedation might be a good option to avoid anesthesia-related risks. A two-injection-point block of the internal and external pinna and acoustic meatus was described in horse cadavers, and it permitted complete stain of all three branches of the great auricular nerve (GAN), internal auricular nerve branch (IAB), lateral auricular branch (LAB), and caudal auricular nerve (CAN), su...
Kearney MT, Kamm JL.To describe the treatment of subcutaneous lipomas in the horse. Methods: 3 horses. Methods: The horses were aged 1 to 2 years old, with lipoma of the abdomen, prepuce, and tarsus. Results: Recurrence of an invasive thoracic lipoma occurred in case 1 at the exit site of a passive drain. The recurrence was treated unsuccessfully with injectable cisplatin, and a second revision surgery with the use of an active drain resulted in resolution. In case 2, complete resection of an encapsulated lipoma of the lateral prepuce was successful with no recurrence. In case 3, incomplete resection of a tarsal ...
Pimenta J, Prada J, Pires I, Cotovio M.Sarcoids and squamous cell carcinomas (SCCs) are the most concerning equine oncological diseases. Both tumors are challenging to manage due to their invasive behavior and high prevalence of recurrences. Furthermore, SCCs have a propensity to metastasize. Programed cell-death ligand 1 (PD-L1) has been one of the main therapeutic targets for immunotherapy in various human tumors. PD-L1 research in equine tumors is scarce and more efforts are necessary to understand the potential of this biomarker as a therapeutical target. Unassigned: Evaluate the immunohistochemical expression of PD-L1 in equin...
