Computed tomographic appearance of equine sinonasal neoplasia

The computed tomography (CT) features of tumors involving the nasal cavity and/or paranasal sinuses of 15 horses were reviewed. The 15 tumors included five neuroendocrine tumors/neuroblastomas, two undifferentiated carcinomas, two myxosarcomas, and one each of nasal adenocarcinoma, hemangiosarcoma, chondroblastic osteosarcoma, anaplastic sarcoma, myxoma, and ossifying fibroma. All tumors except the ossifying fibroma were iso- or hypoattenuating relative to masseter muscle. Thirteen of the fifteen tumors exhibited moderate or marked osteolysis of adjacent cortical bone and 14/15 were characterized by destructive changes of the nasal turbinates, nasal septum, and/or infraorbital canal. Ten horses had moderate or marked involvement of the cribriform plate and six had clear intracranial extension of the mass. CT features were compared to radiographic findings for 10 horses. A mass was observed in 10/10 radiographic studies and mass within the caudal maxillary sinus (7/8) and rostral maxillary sinus (6/7) was identified correctly in most horses. The radiographs were least sensitive for identifying masses within the sphenopalatine sinus (0/5), cranium (0/4), and retrobulbar space (1/7) compared to CT. The radiographs also underestimated potential features of malignancy, such as severity of osteolysis or osseous production. While radiographs are a useful screening tool for identification of sinonasal masses, CT provides greater information regarding mass extent, features of malignancy, and important prognostic indicators.     

Anaplastic malignant melanoma of the tail in non‐grey horses

Information regarding signalment, clinical findings, treatment and outcome of 5 previously reported cases of anaplastic malignant melanoma of the tail in non‐grey horses and of 5 additional cases are summarised. Age was recorded for 9 horses and mean age was 16 years, range 8–23 years. Gender was recorded for 8 horses and 6 of these 8 horses were male horses over 14 years of age. The most common coat colour was bay (6 horses). Other coat colours were palomino (one horse), chestnut (one horse) and black (one horse); coat colour of one non‐grey horse was not specified. Follow‐up information was available for 9 horses and only one horse, a palomino, survived more than 10 months following diagnosis and tail amputation. Surgical excision, including tail amputation and medical therapy with oral cimetidine, was not effective in non‐grey, non‐palomino horses. Tumour recurred on tail tissue remaining after amputation in 2 horses, widespread metastases were documented in 4 cases and metastasis was suspected at the time of death or euthanasia in 3 cases, including one case with amputation site regrowth. No subjective histopathological differences were detected in the palomino horse that survived as compared to horses of other coat colours. Findings suggest that anaplastic malignant melanoma of the tail in non‐grey horses is most often a very aggressive neoplasm, but that there are rare exceptions.     

Calcified tumours of the paranasal sinuses in three horses

Three horses, a 10-year-old Thoroughbred mare, a 9-year-old Thoroughbred gelding and a 6-year-old Arab gelding, with calcified tumours of the paranasal sinuses, are described. All horses presented with purulent nasal discharges and facial distortion. Exophthalmos, blepharospasm and ocular discharge were also a feature in individual horses. A presumptive diagnosis of a calcified tumour was made on the basis of clinical signs and radiographic and endoscopic findings. The tumours ranged from 15 to 25 cm in diameter. A large frontonasal bone flap was used to expose the tumours, which were cleaved into several pieces with an osteotome and removed. Histological examination of the masses identified cementomas in two cases and an osteoma in the third. Long term follow up from 18 months to 5 years after surgery indicated that there was no recurrence. This case series demonstrates that, although calcified tumours of the paranasal sinuses are rare in horses, they should be considered in the differential diagnosis of purulent nasal discharge, facial swelling and ocular distortion, and are amenable to surgical treatment.     

Squamous cell carcinoma of the paranasal sinuses in two horses

This case report describes the history, clinical findings, diagnostic imaging (including computed tomography), gross pathology and histopathology of 2 cases of squamous cell carcinoma in the paranasal sinuses. Radiography of the skull is a useful tool to detect a mass in the paranasal sinuses, but the position, extent and character of the lesion can be better visualised with computed tomography.     

Congenital hypodontia in three horses diagnosed by computed tomography

Dental agenesis is a congenital disease defined as failure of formation of one or more teeth, which has been extensively described in human literature and that has been documented in several other species including cats, dogs, seals and sea lions, mice, and ungulates. The aim of this study was to review the clinical and computed tomographic (CT) features of tooth agenesis in a population of horses. Retrospective review of the imaging records from the Langford Equine Hospital was performed, including all horses that underwent head CT between January 2015 and June 2017. Of a total number of 167 CT scans, three horses with hypodontia were found. All three cases had agenesis of the maxillary 08s and one case had additional agenesis of the 307 and 308 teeth. Delayed resorption of the corresponding deciduous teeth was reported in all cases. The empty space left by the absent teeth was filled either by heterogeneous bone tissue alone (two cases) or by a combination of bone and soft tissue (one case). Alignment between teeth was preserved, and there was no displacement of the neighbouring teeth adjacent to the agenesis site. All three horses presented a symmetric pattern of dental agenesis within the maxillary arcades. The maxillary 08s, which are the latest to erupt, were the most affected teeth. This was similar to that reported in human literature, where the teeth that form later during development are the most vulnerable to dental agenesis.     

Computed tomography of the upper cheek teeth in horses with infundibular changes and apical infection

Reasons for performing study: Infundibular changes are frequently encountered computed tomographic studies of the equine maxillary cheek teeth but the possible importance of this finding is not known. Infundibular caries is a possible cause for pulpitis and apical infection in some horses. Objectives: To study the relationship between the 2 pathologies and the frequency of changes. Methods: The maxillary cheek teeth 108‐ 208 , 109–209 and 110–210 of 25 horses were evaluated using computed tomography and both the prevalence of infundibular and apical infection changes as the possible link with apical infection evaluated statistically. Results: The prevalence of infundibular changes was high in both normal and diseased teeth. Both apical infection and the occurrence of infundibular changes were more prevalent in 109–209 and 110–210. In spite of this, the 2 processes could not be linked to one another. No differences were noted between the left and right sides. Conclusions: A direct relationship between the 2 processes was not established statistically and other underlying causes for the high occurrence of both apical infection and infundibular changes in diseased and normal 108‐ 208 , 109–209 and 110210 are considered.     

Vestibulovaginal leiomyosarcoma in a mare

A 14-year-old Quarter Horse mare presented for a mass within the vestibule and vagina resulting in external compression and incomplete occlusion at the external urethral opening with subsequent difficulty urinating. Examination revealed an approximately 15 × 10 cm lobulated mass within the vestibule and caudal vagina attached via a broad base dorsally. Histopathology of the mass identified a low-grade leiomyosarcoma. Complete resection was not possible, and surgical debulking of the mass was performed during standing sedation using a vessel-sealing and dividing device. The mare was discharged 3 days post-operatively without any complications. Recheck examinations performed at 1 month and 8 months’ post-surgery revealed excellent healing of the surgical site and no apparent tumour regrowth.     

Fibromatous epulis and peripheral odontogenic fibroma in horses

Fibromatous epulis is a rare tumour in horses which is analogous to the same condition in dogs and peripheral odontogenic fibromas in man. The nomenclature is varied throughout the veterinary literature, but these tumours are most correctly known as peripheral odontogenic fibromas. Although these lesions are benign, they have a high recurrence rate in other species, so wide local excision is important to give the best possible prognosis.     

Osteosarcoma in the femur of a horse

A 27-year-old Arabian pony gelding presented for evaluation of weight loss, intermittent sheath oedema, persistent neutropenia and thrombocytopenia, and acute left hindlimb swelling and gait abnormality. Clinical findings included swelling, heat and sensitivity localised over the left greater trochanter, mild to moderate ventral and sheath oedema, a left hindlimb post-legged gait, and off-loading of weight from the left hindlimb at rest. Initially, neutropenia and thrombocytopenia were confirmed on bloodwork, but neutrophilia and thrombocytopenia persisted as the case progressed. Diagnostic imaging (radiography and percutaneous ultrasonography) of the left hindquarters revealed an aggressive, mixed proliferative and lytic bony lesion of the proximal left femur as well as associated muscle fibre disruption and a soft tissue mass. A percutaneous core biopsy of the lesion led to the diagnosis of osteoblastic osteosarcoma on histopathology. Pain and inflammation associated with the lesion was medically managed in the hospital with mild improvement. Additionally, palliative radiation was performed under general anaesthesia. Unfortunately, before a response to palliative radiation could be assessed, the patient was subjected to euthanasia due to development of acute neurological signs.     

Epithelial inclusion cysts of the frontal bones in three horses

In this article, development of a fluctuating swelling in the middle of the frontal region is reported in 3 horses. Clinical and radiological examinations showed them to be palpably soft, nonpainful, well circumscribed and homogeneous. The diagnosis of a cyst‐like lesion is based on centesis and histology. This report describes the clinical features, surgical treatment, outcome and histological findings in all 3 cases.     

Computed tomography of normal cranioencephalic structures in two horses

The purpose of this investigation was to define the anatomy of the cranioencephalic structures in horses using computed tomography (CT). Transverse images of two isolated equine cadaver heads were obtained using a Toshiba 600 HQ (third-generation equipment TCT). CT images were compared to corresponding frozen cross-sections of the cadaver head. Relevant anatomical structures were identified and labelled at each level. The resulting images provided excellent anatomic detail of the structures of the central nervous system and associated formations. Annotated CT images from this study are intended as a reference for clinical CT imaging studies of the equine head.     

Pharmacokinetics of three formulations of vitacoxib in horses

The pharmacokinetic properties of three formulations of vitacoxib were investigated in horses. To describe plasma concentrations and characterize the pharmacokinetics, 6 healthy adult Chinese Mongolian horses were administered a single dose of 0.1 mg/kg bodyweight intravenous (i.v.), oral paste, or oral tablet vitacoxib in a 3-way, randomized, parallel design. Blood samples were collected prior to and at various times up to 72 hr postadministration. Plasma vitacoxib concentrations were quantified using UPLC-MS/MS, and pharmacokinetic parameters were calculated using noncompartmental analysis. No complications resulting from the vitacoxib administration were noted on subsequent administrations, and all procedures were tolerated well by the horses throughout the study. The elimination half-life (T_1/2λz) was 4.24 ± 1.98 hr (i.v.), 8.77 ± 0.91 hr (oral paste), and 8.12 ± 4.24 hr (oral tablet), respectively. Maximum plasma concentration (C_max) was 28.61 ± 9.29 ng/ml (oral paste) and 19.64 ± 9.26 ng/ml (oral tablet), respectively. Area under the concentration-versus-time curve (AUC_last) was 336 ± 229 ng hr/ml (i.v.), 221 ± 94 ng hr/ml (oral paste), and 203 ± 139 ng hr/ml, respectively. The results showed statistically significant differences between the 2 oral vitacoxib groups in T_max value. T_1/2λz (hr), AUC_last (ng hr/ml), and MRT (hr) were significantly different between i.v. and oral groups. The longer half-life observed following oral administration was consistent with the flip-flop phenomenon.     

Treatment of a poorly differentiated sarcoma in the oropharynx of a horse

A 10-year-old Thoroughbred mare was referred to Tennessee Equine Hospital for evaluation and treatment of a subepiglottic mass. Physical and laboratory examinations revealed no other abnormalities. The tumour was excised through a laryngotomy site using transendoscopic laser and sharp excision. Histological evaluation revealed a poorly differentiated sarcoma with features of a leiomyosarcoma, a rarely identified neoplasm in the oropharynx of the horse. The mare developed intermittent dorsal displacement of the soft palate (iDDSP) after surgery but was able to resume full training. There was no evidence of regrowth 8 months post-operatively.