Primary corneal melanocytoma in a Collie.

A 6-year-old female, spayed Collie was referred to the Western College of Veterinary Medicine for a 12-month history of a progressive right corneal mass. A superficial keratectomy was performed and histopathology revealed a corneal melanocytoma with complete excision. There has been no recurrence of the neoplasm to date (12 months). This is the first known report of an isolated corneal melanocytoma in a canine.

A case of a canine pigmented plaque associated with the presence of a Chi-papillomavirus.

The seven fully described canine papillomaviruses (CPVs) have been allocated by sequence comparison and other genetic features into three phylogenetic clades. This largely reflects clinical findings, so each sequence of a newly discovered CPV in combination with clinical and pathological details is a valuable piece of evidence. We hypothesize that the genomic sequence of a new CPV can help to predict clinical features and progression, and that this can be tested in subsequent cases. In this case, a 2-year-old female dachshund-mix presented with papillomatosis clinically and histologically characterized as pigmented viral plaques. PCRs using primers evaluated for CPVs successfully amplified papillomavirus (PV) DNA. Sequencing of the products revealed an unknown PV putatively belonging to the PV genus Chi. Rolling circle amplification was used to amplify the entire viral genome. Sequencing revealed a novel PV, designated as CPV8, which was most closely related (63% homology) to the recently discovered CPV4. CPV4 is associated with benign pigmented plaques in pugs. Phylogenetic analysis based on the nucleotide sequences of four viral genes showed that the novel virus was closest to CPV3, CPV4 and CPV5. The presence of viral DNA was confirmed in the lesions by in situ hybridization using specific probes. CPV8 may consequently be regarded as the fourth member of the Chi-papillomavirus genus. All viruses belonging to this genus induce pigmented plaques in dogs. These findings support the hypothesis that genomic sequences can be useful in predicting the clinical features of CPV infection.

Equine skin tumours in 20 horses resembling three variants of human melanocytic naevi.

Melanocytic tumours are important in horses, especially grey horses. Intradermal common melanocytic naevi, cellular blue naevi and combined cellular blue naevi are subgroups of human melanocytic tumours, which have not been reported in horses. In this study, we describe 20 horses with skin tumours similar to these naevi of humans. These tumours represented individual skin masses in male and female horses of different breeds. Tumours resembling human intradermal common melanocytic naevi were noted in 12 horses aged between 2 and 17 years. Seven horses aged between 4 and 15 years developed cutaneous lesions similar to human cellular blue naevi. A combined cellular blue naevus-like tumour was diagnosed in a 20-year-old horse. All tumour types formed expansile, well-demarcated, non-encapsulated, symmetrical masses. Tumours similar to intradermal common melanocytic naevi were composed of nests of round and spindeloid neoplastic cells, often embedded in myxomatous stroma. Lesions resembling cellular blue naevi were formed by intradermal bundles of ovoid to elongated cells separated by collagen fibres. The combined cellular blue naevus-like tumour resembled human cellular blue naevus with in addition, an overlying junctional common melanocytic naevus. Neoplastic cells in all groups contained varying amounts of melanin pigment and were immunopositive for S100. These equine skin tumours differ from the commonly recognized equine melanocytic tumours by their cytomorphological features, random location and the absence of an increased tumour frequency in grey horses. The resemblance of these tumours to three distinct subgroups of human naevi expands the complexity of equine proliferative cutaneous melanocytic lesions.

Surgical management of a progressive iris melanocytoma in a Mustang.

CASE DESCRIPTION: A 7-year-old gray Mustang gelding weighing 454 kg was presented for evaluation of a brown mass within the left eye (OS) of 1 year's duration with recent enlargement. CLINICAL FINDINGS: A nonpainful, 8 mm diameter, brown, vascularized mass was identified in the anterior chamber of the OS. Ocular B-scan ultrasound confirmed iris involvement and corneal endothelial contact. Histopathology confirmed the presumptive diagnosis of a uveal melanocytic neoplasm, and revealed 1-3 mitotic figures per high power (400x) field. TREATMENT AND OUTCOME: The mass was removed via sector iridectomy without complications, but without complete margins. Three cutaneous melanocytomas noted 1.5 months postoperatively were completely excised. No tumor regrowth was noted 15 months postoperatively, supporting a diagnosis of melanocytoma for the iridal mass. CLINICAL RELEVANCE: Sector iridectomy is a reasonable treatment option for uncomplicated iridal melanocytomas in horses. Mitotic index and presence of cutaneous melanocytic neoplasms may be irrelevant to the prognosis of equine iridal melanocytic neoplasms.

Detection of a novel papillomavirus in pigmented plaques of four pugs.

Pugs are predisposed to the development of deeply pigmented, slightly elevated hyperkeratotic noncancerous plaques. Polymerase chain reaction amplification of a papillomavirus (PV)-like DNA fragment from such lesions suggested that PV may be responsible for them, although the predicted virus has not yet been identified. The goal of the present study was to make use of pigmented plaques from four pugs to identify and sequence the predicted virus. Taking advantage of the circular nature of PV DNA, the entire viral genome was amplified by rolling circle amplification and restriction enzyme analysis disclosed the same pattern in all four cases. Sequencing of one of the amplificates revealed a novel canine PV, termed CPV4, related to the recently described CPV3 but clearly distinct from canine oral PV and CPV2. Thus, a novel canine PV and a method for its future diagnosis are described.

Unusual presentation of an anterior uveal melanocytoma in a 3-year-old poodle.

A poodle was referred for evaluation of a pigmented mass in the right eye. The differential diagnoses included an ocular melanoma or ocular melanosis. The right eye was removed and an anterior uveal melanocytoma was confirmed on light microscopical examination.

Survey of equine cutaneous neoplasia in the Pacific Northwest.

A retrospective study examined data regarding equine cutaneous and mucocutaneous neoplasms submitted to the Veterinary Diagnostic Laboratory at Oregon State University in a 3.5-year period. A total of 536 neoplasms were identified, accounting for 30% of the total equine pathology submissions. Sarcoid, squamous cell carcinoma, melanocytic tumors, papillomas, and mast cell tumors were the most common neoplasms, constituting 87.5% of all cutaneous neoplasms. Sarcoids represented 51.4% of all neoplasms and 15.18% of total equine accessions. Sarcoid was most common in paints, quarter horses, and Arabians, and was the only common tumor in donkeys and mules. Mean age at diagnosis of equine sarcoid was 9 years. Squamous cell carcinoma constituted 18.3% of all neoplasms and 5.41% of total equine accessions. Ocular squamous cell carcinoma was most common in paints and quarter horses, and penile/preputial squamous cell carcinoma was most common in appaloosas and quarter horses. The mean age of horses with ocular squamous cell carcinoma (13 years) and squamous cell carcinoma of the skin (15 years) was significantly less (P < 0.5) than that of horses with squamous cell carcinoma of the penis and prepuce (21 years) or vulva, anal, and perianal skin (19 years). Findings suggest that equine sarcoid and squamous cell carcinoma occur more frequently in the Pacific Northwest than in the northeastern United States.

Pigmented cutaneous papillomatosis (pigmented epidermal nevus) in three pug dogs; histopathology, electron microscopy and analysis of viral DNA by the polymerase chain reaction.

Canine pigmented epidermal nevus (CPEN) is a skin disorder of some breeds of dog characterized by multiple black plaques of the haired and non-haired skin. Three cases of pigmented cutaneous papillomatosis (previously described also as CPEN) in pug dogs were investigated histopathologically, immunohistochemically and electron microscopically. Additionally, DNA analyses with the polymerase chain reaction (PCR) were performed in two cases. Many nuclei of the stratum granulosa were diffusely immunolabelled for specific structural antigens of bovine papillomavirus (subgroup A), but nuclear inclusion bodies were not detected by retrospective examination of haematoxylin and eosin-stained sections of the affected skin. Aggregates of small numbers of viral particles (ranging from 37 to 43 nm in diameter) with a hexagonal structure were sparsely scattered throughout the nuclei of some of the superficial keratinocytes. PCR amplification targeted for the L1 gene of papillomavirus cloned from a case of CPEN yielded an expected fragment of 194-bp in the two CPEN cases examined but not in a case of canine oral papilloma.

Equine melanoma in a population of 296 grey Lipizzaner horses.

REASONS FOR PERFORMING STUDY: Equine melanomas occur most commonly in grey horses at age 5 years or more. Generally, benign and malignant melanomas are distinguished by microscopy, but a more distinct classification would be helpful. OBJECTIVES: The objectives of this study were to gain further evidence concerning the occurrence of melanotic tumours, and to evaluate the impact of heredity on melanoma development. METHODS: A clinical study was conducted on a defined population of 296 grey horses of Lipizzaner breed. Individuals were classified according to their stage of disease using a 0-5 scale. Heritability was estimated on a sample of 296 grey horses with pedigrees traced back as far as 32 generations. RESULTS: Of the 296 horses, dermal melanomas were present in 148 horses (50%), 68 of which were more than age 15 years; 51 of these were melanoma-bearing. In 75.6% of cases, melanotic tumours were detected underneath the tail. Although melanoma-bearing grey horses were encountered up to stage 4, none of the affected individuals suffered any severe clinical effect or was handicapped in performance. Statistical analysis revealed highly significant effects of stud and age (P < 0.0001), explaining 28% of the total variability. CONCLUSIONS: In contrast to melanomas in solid-coloured horses characterised by early metastases, melanomas in grey horses showed less malignancy. Affected individuals often had encapsulated nodules or structures similar to human blue nevi. Grey horse-specific genetic factors inhibiting metastatic processes may be responsible for this phenomenon. POTENTIAL CLINICAL RELEVANCE: Although the obtained heritability estimate of 0.36 with a standard error of 0.11 indicates a strong genetic impact on the development of melanoma in ageing grey horses, a possible influence of the genes with large effects was also suggested. Therefore, further analysis is required of melanoma development in the ageing grey horse.

Molecular characteristics of cutaneous papillomavirus from the canine pigmented epidermal nevus.

To investigate the relation between the canine pigmented epidermal nevus (PEN) and cutaneous papillomavirus, we cloned and sequenced the L1 gene of papillomavirus from the canine pigmented epidermal nevus (PEN). Amplification of DNA sample with the L1 consensus primers yielded an expected fragment of approximately 450-bp. The nucleotide sequences of the fragment showed about 64% of sequence similarity to the L1 region of human papillomavirus isolate CP6108 and less than 57% sequence similarity to those of canine oral papillomavirus (COPV). In situ hybridization determined the presence of papillomavirus DNA mainly in the upper stratum granulosum of skin in this case. The results indicated that the canine cutaneous papillomavirus from the PEN lesion was genetically close to human papillomavirus rather than COPV.

Spontaneous regression of cutaneous melanoma in sinclair swine is associated with defective telomerase activity and extensive telomere erosion.

Recently we proposed the hypothesis that extensive telomeric association of chromosomes is an early manifestation of cell death and asked whether there are extensive telomeric associations present in metaphases of the spontaneously regressing Sinclair swine cutaneous melanoma (SSCM). Our results indicate that early passage SSCMs, in the accelerated growth phase, do not show telomeric associations but do have numerical and other specific structural abnormalities. However, the same melanoma cell lines at late passages or melanomas obtained from middle- and old-aged Sinclair swine show extensive telomeric associations in the form of dicentric, multicentric, and ring configurations. Such abnormal structures are present mostly in metaphases that are hyperploids. Increasing frequencies of apoptotic bodies were also observed in higher passage tumor cell lines obtained from younger animals or in melanomas obtained from older animals. The polymerase chain reaction (PCR)-based telomeric repeat amplification protocol (TRAP) assay shows no detectable telomerase activity in any of these regressing swine melanoma cell lines, neither in normal swine skin fibroblasts nor in nevi. However, the fetal swine (i.e., non-regressing) melanoma cells show telomerase activity. Fluorescence in situ hybridization (FISH) results using the commercially available human telomeric repeat DNA probe indicate a reduction of telomeric signals in metaphase and interphase cells of regressing melanomas. From these observations we conclude that spontaneous regression of SSCM is associated with the loss of telomerase activity and a reduction of telomeric repeats that results in the formation of multicentric and ring configurations. Such abnormal chromosome configurations are lost, following the breakage-fusion-bridge-cycles, and result in extensive DNA fragmentation, as shown by laddering experiments, and, finally, cell death.

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.

A giant congenital pigmented nevus in a horse.

Pigmented nevi have not been widely recognized in domesticated animals. We describe, for the first time, a giant congenital pigmented nevus in a horse. Because of a prominent neuroid component within the lesion, neurofibromatosis was the major differential diagnosis.

On the natural history and comparative pathology of the blue naevus.

In man the epidermis is the final destination for most of the melanocytes which are of neural crest origin, and they migrate to a variety of sites. Dermal melanocytic distribution, conspicuous in some lower animals, has a very restricted normal distribution in man, and of the variety of anomalies which exist the blue naevus is the most frequently encountered. It is comparable to the common melanocytoma of dog and hamster. More widespread dermal melanocytoses are rare, and a unique case in which death from melanoma supervened, recently recorded by the author, is an example of a syndrome the only parallel to which appears to be equine melanotic disease, a disorder of aging, greying horses. It is argued on comparative grounds that the newly described syndrome and equine melanotic disease are examples of a neurochristic disorder involving the cephalad segments and dermal melanocytes.

[Simultaneous occurrence of structurally variegated cutaneous nevi in the dog]. / Soucasný výskyt strukturálne pestrých kozních nevu u psa.

In a boxer dog aged 12 years who had deceased from circulatory insufficiency due to purulent endomyocarditis, there occurred a Leydig cell adenoma of the testis and multiple cutaneous naevi (haemangioma, pigmented naevus and various cutanous organ naevi). The findings have been discussed with reference to the race disposal to neoplastic growth.