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.     

Conjunctival malignant melanoma in a horse

A case of malignant melanoma originating from the conjunctiva of a horse is reported. The tumor exhibited locally aggressive behavior as evidenced clinically by recurrence following two treatment episodes including surgical excision on each occasion and one application of cryotherapy. The orbit was subsequently exenterated and histologically malignant conjunctival melanoma was confirmed. Histopathologic features included variable pigmentation with amelanotic sites demonstrating marked cellular and nuclear pleomorphism with high numbers of mitotic figures. Cords of neoplastic cells invaded the sclera and cornea. Following exenteration, the horse exhibited no recurrence of the tumor for five years before being lost to follow-up. To our knowledge, this is the first report of primary malignant conjunctival melanoma in a horse.     

Chronic lameness caused by vascular compression of the iliac artery and vein by a malignant melanoma in the pelvis of a grey Spanish gelding

An 11-year-old grey Spanish gelding was presented with chronic lameness of the right hindlimb, with abduction of the limb during the swing phase. Based on a comprehensive lameness examination, the problem was localised to the pelvic region. Rectal and ultrasonographic examinations revealed a mass in the pelvic region in close association with the iliac artery and vein, and ultrasonographic indications of vascular compression. Considering the clinical presentation of a grey middle-aged horse with multifocal melanoma-like nodules at the level of the perineum, tail base, preputium and penis, a malignant melanoma with secondary vascular or neurological compression was suspected. Post-mortem and histological examination confirmed the diagnosis of malignant melanoma with vascular compression of the iliac artery and vein and infiltrative growth in the iliac vein.     

Unilateral malignant melanoma of the adrenal gland with metastatic spread to the thorax in a horse

A 7-year-old grey horse that had a history of inappetence, weight loss, weakness, dyspnoea, coughing and intermittent colic was examined post-mortem. A melanoma, confirmed histologically, was found in the right adrenal gland and had eroded into the posterior vena cava. Thoracic metastases were also identified. The skin, including the legs, trunk and perineum was normal with no evidence of melanomas. This was considered to be a primary, malignant melanoma, a novel finding in the adrenal gland of the horse.     

Equine Melanocytic Tumors: A Retrospective Study of 53 Horses (1988 to 1991)

A study of 57 cutaneous melanocytic tumors from 53 horses revealed 4 distinct clinical syndromes: melanocytic nevus, dermal melanoma, dermal melanomatosis, and anaplastic malignant melanoma. Melanocytic nevus and anaplastic melanoma each had histopathologic features that distinguished them from dermal melanoma and dermal melanomatosis. Dermal melanoma and dermal melanomatosis were histologically similar but could be differentiated by their clinical features. Melanocytic nevi were diagnosed in 29 horses with an average age of 5 years; they were solitary, superficial masses that occurred in both grey and nongrey horses, and in which surgical excision was generally curative. Dermal melanomas were diagnosed in 20 horses with an average age of 13 years; all horses of known coat color were grey. Eight horses with an average age of 7 years had 1 or 2 discrete dermal melanomas. Follow-up information was available for 6 horses; metastases occurred in 2 horses, and surgical excision was apparently curative in 4 horses. Dermal melanomatosis was diagnosed in 12 grey horses with an average age of 17 years; all 6 of these horses evaluated had internal metastases. In 2 aged nongrey horses with anaplastic malignant melanoma, the tumors metastasized within 1 year of diagnosis. Two tumors with features of both melanocytic nevus and dermal melanoma remained unclassified.     

COMPUTED TOMOGRAPHIC APPEARANCE OF MELANOMAS IN THE EQUINE HEAD: 13 CASES

Melanomas are one of the most common neoplasms in the horse and are frequently found in the head region. There is a genetic predisposition in horses with a gray hair coat. Computed tomography (CT) is frequently used in referral practice to evaluate the equine head but there are few reports describing the CT appearance of melanomas in this location. The aim of this retrospective, case series study was to describe characteristics in a group of horses with confirmed disease. Case records from two referral hospitals were reviewed, and 13 horses were identified that had undergone CT of the head, with a diagnosis of melanoma based on cytology, histopathology, or visual assessment of black (melanotic) tissue. A median of 11 melanomas was identified per horse (range 3–60), with a total of 216 masses. Melanomas were found most frequently in the parotid salivary gland, guttural pouches, surrounding the larynx and pharynx and adjacent to the hyoid apparatus. In noncontrast CT images, all melanomas were hyperattenuating (median; 113.5 Hounsfield units (HU), IQR; 26 HU) compared to masseter musculature (median; 69 HU, IQR; 5.5 HU). Fifty‐six (25.9%) masses were partially mineralized and 41 (19.4%) included hypoattenuating areas. Histopathological assessment of these melanomas suggested that the hyperattenuation identified was most likely a result of abundant intracytoplasmic melanin pigment. Melanomas of the equine head appeared to have consistent CT features that aided detection of mass lesions and their distribution, although histopathological analysis or visual confirmation should still be obtained for definitive diagnosis .     

Malignant melanoma of the third eyelid in a horse

An 8‐year‐old grey Quarter Horse gelding was referred for evaluation of a rapidly growing mass associated with the third eyelid of the left eye. A pigmented mass of approximately 2 cm in diameter was palpated and visualised associated with the conjunctival lining of the nictitans. It was not possible to palpate normal nictitans deep to the base of the mass. A full dermatological examination revealed no other melanomas in common sites. Based on the size and rapid growth of the mass, surgical excision and one application of local chemotherapy was performed under general anaesthesia. Histopathology confirmed the diagnosis of malignant melanoma and the presence of clean surgical margins. There was no recurrence at 5 weeks post surgery. To our knowledge, this is the first report of a primary malignant melanoma of the third eyelid in a horse.     

Three neoplasms in a Eurasian otter (Lutra lutra): malignant melanoma,trichoblastoma and mammary gland adenoma

An eighteen-year-old female Eurasian otter became emaciated and died. Necropsy examination revealed nose and thoracic cutaneous masses, abdominal subcutaneous mass, and multiple nodules in the liver and lungs. Malignant melanoma was found in the nose cutaneous mass and to have metastasized to the liver, lungs, kidneys, adrenal glands, mammary glands and left mandibular lymph node. The neoplastic cells were labeled for vimentin, melanoma, and S100. The cutaneous mass in the thoracic area consisted of spindle shaped neoplastic epithelial cells and was diagnosed as trichoblastoma. Mammary gland adenoma was observed in the abdominal subcutaneous mass. This is the first report of primary three neoplasms of malignant melanoma, trichoblastoma and mammary gland adenoma in a Eurasian otter.     

Circulating melanin-containing cells and neutrophils with phagocytized melanin granules in a horse with disseminated melanoma

An 18-year-old, grey, Thoroughbred Cross gelding was referred to the Cummings School of Veterinary Medicine at Tufts University following a 3-week history of low-grade fever of unknown origin, distal limb swelling, and weight loss. Clinical examination identified a few black, round, smooth nodules along the ventral aspect of the proximal tail. Transabdominal ultrasound showed a markedly enlarged heterogenous spleen, hyperechoic liver nodules, and evidence of peritonitis with fibrin deposition. A mature neutrophilia was noted on complete blood count with variable numbers of phagocytized granules within neutrophils. The granules did not stain with Perl's Prussian blue, and were intensely positive when stained with Fontana-Mason, consistent with melanin. On necropsy, the spleen occupied approximately one-third of the abdominal cavity and was diffusely firm with abundant black pigment on cut section. The medullary space of the 18th thoracic vertebra was also diffusely blackened. The splenic, mediastinal, and tracheobronchial lymph nodes were five times the normal size and diffusely pigmented. The final anatomic diagnosis was disseminated malignant melanoma with extensive splenic involvement and hemolymphatic and vascular neoplastic dissemination. To the authors' knowledge, this is the first full report to identify circulating neutrophils containing phagocytized melanin granules, which confirmed an antemortem diagnosis of disseminated melanoma.     

Malignant melanoma in the foot of a horse

A 24-year-old horse had a malignant melanoma of the right forefoot. Because surgical excision of the melanoma was incomplete, as determined by histologic examination of the excised tissue margins, the tumor margins were injected with a matrix therapeutic implant containing cis-diamminedichloroplatinum, epinephrine, and purified bovine collagen matrix. The foot healed and the horse remained clinically free of disease for 26 months before recurrence of malignant melanoma. Surgical exploration of the digit revealed extensive involvement of the foot, and the horse was euthanatized.     

An Equine Intersex with Unilateral Gonadal Agenesis

Cytogenetic and histological studies have been carried out on an intersex horse which was clinically diagnosed as a cryptorchid. The horse had the general conformation of a stallion but the external genitalia included a well developed vulva and a penis. The right testis which was descended was devoid of germ cells and the left “gonad” located in the cavum vaginale contained neither testicular nor ovarian tissue. The male duct system on both sides were relatively well developed despite the absence of a testis on the left side. Chromosome analysis on cultured cells from the descended testis revealed the presence of four chromosomally-distinct cell types with XX, XY, XXY and XO sex complements indicating a quadruple mosaicism. The presence of polymorphonuclear neutrophils exhibiting a drumstick, in the hemopoietic tissues and a sex chromatin body in the nucleated cells of buccal mucosa suggest that mosaicism prevails in other somatic tissues of the horse. On the basis of information derived from similar conditions in humans and some domestic animals it would appear that this horse resulted from an XXY zygote. The four cell types noted in the horse probably resulted through mitotic mechanisms favouring the loss of an X and a Y at different stages during embryonic development. The absence of gonad on the left side of this horse might be causally related to the preponderance of XO cell types in the somatic blastema during early gonadal differentiation.     

Primary corneal malignant melanoma in a horse

A 13-year-old Missouri Fox Trotter gelding of chestnut colour was referred for a 6-week history of blepharospasm and epiphora of the left eye. Due to the presence of irregular corneal masses, superficial keratectomy was performed along with adjunctive strontium-90 beta irradiation and subsequent topical mitomycin C chemotherapy. A diagnosis of poorly melanised malignant melanoma was made based on histopathological examination and immunohistochemistry. There has been no recurrence of the neoplasm over 10 months of follow-up. To the authors' knowledge, this is the first documented case of a primary corneal melanocytic neoplasm in a horse.     

Population Statistics and Biological Traits of Endangered Kiso Horse

The objective of this study was to clarify the current status of endangered Kiso horse, population statistics and biological traits, in order to take a step for the conservation by scientific approach. We surveyed 125 Kiso horses (86.2% of the whole breed), analyzed the construction of the population, and calculated the coefficient of inbreeding and effective population size. Moreover, we confirmed coat color variations and the traditional traits of the Kiso horse, and measured their height at the withers and chest circumference to clarify their physical characteristics. The population pyramid of the horses was stationary or contractive, suggesting a reduction of the population in the near future. The effective population size of the horse (47.9) suggested that the diversity was much less than their census size, and the high coefficient of inbreeding, 0.11 ± 0.07 on average, suggested that the horses were surely inbred. The horses had only 4 coat colors; bay, dark bay, buckskin dun, and chestnut, and 116 horses (92.8%) were bayish color, suggesting the fixation in their coat color. Moreover, the majority of them had dorsal stripe (83 horses; 66.4%), and the average heights at withers(131.9 ± 4.4 cm) and chest circumference (167.1 ± 10.1 cm) were not significantly different between males and females.     

Rhinotomy to access lesions within the nasal cavity of two horses

Most lesions that affect the nasal cavity of the horse can be accessed via the nostril or via a frontonasal sinus flap but occasionally, surgical access to the mid‐portion of the nasal cavity is necessary. This case report describes the use of a centrally based, 3‐sided rhinotomy which provided good access to the ipsilateral nasal cavity and allowed for removal of abnormal tissue/foreign material in two horses. The nasal bone flap was preserved and only relatively mild intraoperative haemorrhage occurred which was controlled with nasal packing. Horses recovered well from surgery with an excellent long‐term cosmetic result.     

Investigation of a progressive facial deformity and stridor in an adult horse with a bone sequestrum and subsequent sinonasal abscess

Advanced diagnostic imaging and histopathological investigation were performed in an adult horse with chronic facial swelling due to a bone sequestrum and abscessation. In contrast to other cases, there were no draining tracts, difficulty eating, weight loss, head shaking, or fistula formation between the oral cavity and the maxillary sinus.     

Transmaxillary anchored silicon embedded gauze plug in the post-operative treatment of a large oromaxillary fistula caused by a supernumerary cheek tooth

A 9-year-old Hungarian sport horse gelding was presented to the clinic in poor condition displaying malodorous bilateral purulent nasal discharge. Oral examination revealed the presence of supernumerary 111 and 211. Bilateral diastema formation between the third maxillary molars and the supernumerary teeth with deep periodontal pockets and massive food impactions were diagnosed endoscopically. Radiography revealed inhomogenous sinus opacities in the left and right paranasal sinuses. Following bilateral oral extractions of the supernumerary cheek teeth and third maxillary molars, bilateral oromaxillary fistula formations were diagnosed (about 17 mm diameter on the right side). Bilateral frontal and right-sided maxillary trephinations and resection of the right bulla of the maxillary septum were performed. Massive food impactions of the left and right paranasal sinuses were removed under endoscopic control. Repeated trans-endoscopic sinus lavage was performed post-operatively. After 2.5 months, the large right-sided oromaxillary communication was temporarily closed with a transmaxillary anchored, gauze-cored silicon plug on an outpatient basis. Follow-up examination after 187 days revealed complete closure of the oromaxillary fistula and absence of sinusitis. In a 1.5-year follow-up control, no pathological conditions were found.     

黑色素皮质激素受体1基因248位点多态性与中国马品种毛色的相关性分析

在欧洲马品种中,黑色素皮质激素受体1(melanocortin receptor 1,MC1R)基因第248位碱基有C/T多态性,纯合的T248位点决定欧洲马的栗毛色。针对MC1R基因的248位点设计了2对特异性引物,采用等位基因特异性PCR技术,研究3个中国马品种MC1R基因型与栗色毛之间的关系。经扩增获得两种DNA片段,克隆测序后证明,扩增片段确为MC1R基因,两种DNA片段序列在基因的248位点的确呈现C/T多态性,但检测126份贵州矮马、西南马和新疆伊犁马血液样本,全部为杂合基因型(Ee),其中包括栗毛、黑毛、骝毛3种单毛色及3种复毛色。这些研究结果提示,MC1R基因中248位点的多态性与国内3个马品种的栗色毛之间没有直接的相关性。     

Canine limbal melanoma: 30 cases (1992-2004). Part 1. Signalment, clinical and histological features and pedigree analysis

OBJECTIVES: (1) To review the signalment, clinical, and histological features of canine limbal melanoma; (2) to perform pedigree analysis on breeds predisposed to limbal melanoma to establish if common ancestry exists; and (3) to investigate if any ancestral relationship exists between canine limbal melanoma and canine anterior uveal melanoma (CAUM). DESIGN: Retrospective study. ANIMALS STUDIED: Thirty dogs with limbal melanoma. METHODS: Medical records of patients were reviewed. Follow-up information was obtained by re-examination of patients or telecommunications with the referring veterinary surgeons or the owners. Pedigrees were analyzed for common ancestry amongst affected dogs. RESULTS The mean age (+/- SD) at diagnosis was 6.2 (+/- 2.75) years with a range from 1 to 11 years. There was a bimodal distribution of ages with a peak at 3-4 years and a peak at 7-10 years. There was no eye predilection or predisposition for sex or coat color. Twenty-five (83%) of the limbal melanomas occurred within a dorsal arc from the dorsomedial to the ventrolateral limbus. Golden retrievers were four times more common in the melanoma group compared to the Animal Health Trust population (P < 0.0001). Labrador retrievers were three times more common in the melanoma group (P=0.01). Pedigree analysis on eight Golden retrievers [limbal melanoma (n=5), CAUM (n=2) and diffuse ocular melanosis (n=1)], revealed a pattern of inter-relatedness consistent with the condition(s) being caused, at least in part, by a genetic mutation(s). A similar level of inter relatedness was evident in six Labrador retrievers (limbal melanoma (n=2) and CAUM (n=4)). In 5/22 cases (23%), histological features suggestive of malignancy were present including intratumor necrosis in 4/22 cases (18%) and cellular atypia in 1/22 cases (5%). CONCLUSIONS: In Golden and Labrador retrievers there is evidence that limbal melanomas, CAUM and ocular melanosis are at least in part heritable and that the same genetic mutation(s) may be causally associated with melanocytic disease at different ocular sites. The same genetic mutation(s) may be present in these two breeds. Histology should be performed on all cases to identify those with greater malignant potential.     

Malignant melanoma in a seagull (Larus fuscus): morphological and immunohistochemical approach

A common seagull (Larus fuscus) was found near the southern coast of Italy by the veterinarians of the local wild animal rescue center. Physical examination of the bird revealed an ulcerated mass involving a majority of the oral cavity; the mass did not allow for normal feeding. After the bird died necropsy was performed and the mass was histologically and immunohistochemically examined. The morphology and the immunoreactivity for Melan-A and S-100 antigens led to a diagnosis of malignant melanoma. This is the first case of malignant melanoma described in a seagull, and herein we compare the characteristics of the present case with malignant melanoma already described in domestic animals.     

Analysis of KIT expression and KIT exon 11 mutations in canine oral malignant melanomas

KIT, a transmembrane receptor tyrosine kinase, is one of the specific targets for anti-cancer therapy. In humans, its expression and mutations have been identified in malignant melanomas and therapies using molecular-targeted agents have been promising in these tumours. As human malignant melanoma, canine malignant melanoma is a fatal disease with metastases and the poor response has been observed with all standard protocols. In our study, KIT expression and exon 11 mutations in dogs with histologically confirmed malignant oral melanomas were evaluated. Although 20 of 39 cases were positive for KIT protein, there was no significant difference between KIT expression and overall survival. Moreover, polymerase chain reaction amplification and sequencing of KIT exon 11 in 17 samples did not detect any mutations and proved disappointing. For several reasons, however, KIT expression and mutations of various exons including exon 11 should be investigated in more cases.