Multiple papillomavirus-associated epidermal hamartomas and squamous cell carcinomas in situ in a dog following chronic treatment with prednisone and cyclosporine

Characterising the expression of the organic cation transporter OCT3 in cutaneous papillomas of dogs

BACKGROUND

The identification of the activation of the mammalian target of rapamycin (mTOR) signalling pathway as a frequent molecular event in canine cutaneous papillomas (CPs) has provided the rational foundation to explore novel molecular-targeted therapies. Recent evidence indicates that metformin reduces the size of CPs in mice by inhibiting the mTOR signalling pathway. These effects require the expression of the organic cation transporter 3 (OCT3/SLC22A3), a well-known metformin uptake transporter.

HYPOTHESIS/OBJECTIVES

The aim of the present study was to characterise the expression pattern of the metformin uptake transporter OCT3 in canine samples of CP that have shown activation of the mTOR signalling pathway in order to predict if this hyperplastic epidermal lesion is potentially sensitive to metformin.

METHODS

The expression of OCT3 was evaluated by immunohistochemical investigation in sections of a previously constructed tissue microarray containing 28 samples of canine CP and compared with that previously evaluated for the mTOR activation marker pS6.

RESULTS

OCT3 was highly expressed in the membrane and cytoplasm of the basal and suprabasal epidermal cells in all samples of canine CP. This OCT3 expression was localised at similar epidermal compartments to those observed for pS6.

CONCLUSIONS AND CLINICAL RELEVANCE

These results show that canine CPs exhibit the expression of surrogate markers that suggest sensitivity to metformin, such as upregulated OCT3 and pS6 expression. Taken together, these findings provide the rationale for the early assessment of the use of metformin as a mechanism-based therapeutic approach for treating canine patients with persistent or multiple CPs.

Clinical, histopathological, and molecular characterization of canine pigmented viral plaques

Canine pigmented viral plaques (PVPs) are proliferative epidermal lesions caused by canine papillomaviruses (CPVs). Although the lesions are benign, neoplastic transformation has been reported. Cases reported in the literature are few and mainly focused on genome sequencing. The aim of this study was to collect data on the epidemiology, clinicopathological features, and genotyping of PVPs. Fifty-five canine PVPs were retrospectively retrieved and histologically evaluated. Follow-up was available for 33 cases. The median age was 6.5 years and pugs were the most represented breed (25%). There were 4 clinical presentations: a single lesion (24%), multiple lesions (75%) in one (41%) or different sites (34%), and generalized lesions all over the body (24%). The abdomen and axillae were the most common sites. In single lesions, no recurrence was observed after conventional surgery, whereas different medical treatments reported for multiple lesions were not successful. Spontaneous regression was reported in 3 cases. Neoplasia in contiguity with PVPs was seen in 5 of 55 lesions (9%), and 1 dog was euthanized due to invasive squamous cell carcinoma (SCC). The most useful histopathological features for diagnosis were scalloped profile, epidermal spikes, hypergranulosis, and hyperpigmentation. L1 immunolabeling was present in 14 of 16 cases (87%). Sequencing revealed that 10 of 16 cases were associated with CPV-9 (71%), 2 cases were associated with CPV-4 (14%), and 2 cases were associated with CPV-8 (14%). In conclusion, this represents a large cohort study on canine PVPs reporting data on clinicopathological features, therapy, outcome, and the type of CPV involved for the first time in Italy.

Lateral rhinotomy and coblation for treatment of a nasal hamartoma in a dog

CASE DESCRIPTION

A 4-year-old spayed female French Bulldog was referred for treatment of a suspected right-sided nasal angiofibroma associated with a 4-month history of unilateral nasal discharge and stertor.

CLINICAL FINDINGS

The dog appeared healthy other than right-sided mucoid debris and decreased airflow through the right naris. The dog was anesthetized, and a large intranasal mass was observed obstructing the right nasal passage and abutting the nasal septum.

TREATMENT AND OUTCOME

A lateral rhinotomy was performed, and rigid endoscopes (0° and 30°) were used to examine the right nasal cavity. The mass filled the anterior aspect of the nasal cavity and involved a portion of the nasal turbinates with some erosion. A coblation unit was used to ablate tumor tissue laterally to remove the tumor in piecemeal fashion. Recovery was routine with only minor epistaxis after surgery, and the dog was discharged the next day. Eight months after surgery, follow-up CT revealed right-sided nasal turbinate and conchal atrophy consistent with prior mass ablation. No macroscopic recurrence was detected, and the owners reported only rare, clear rhinorrhea.

CLINICAL RELEVANCE

Findings suggested that coblation may be an alternative to radiation therapy for vascular tumors with minimal invasion and low metastatic potential.

Expression of the hippo signalling pathway effector YAP during canine epidermal tumourigenesis

Cutaneous papilloma (CP) and cutaneous squamous cell carcinoma (CSCC) are frequent epidermal tumours in dogs. In this regard, the study of the deregulated activity of signalling molecules during the epidermal tumourigenesis process could be the basis for the development of novel molecular mechanism-based antitumour treatments for CP and CSCC canine patients. Recent evidence suggests that the development and progression of CP and CSCC involve the dysregulated activation of the Hippo signalling pathway effector YAP. Thus, in the present study, we evaluated the immunohistochemical expression pattern of YAP in sections of tissue microarrays constructed from canine samples of normal epidermis, CP, preneoplastic epidermis, and CSCC. In samples of CP, preneoplastic epidermis, and CSCC, YAP expression was significantly increased relative to normal epidermis. This emerging evidence suggests that the dysregulated activity of the Hippo signalling pathway effector YAP represents a frequent event during canine epidermal tumourigenesis, pointing to this protein as a potential therapeutic target for the treatment of CP and CSCC in dogs.

Aberrant Expression of E-cadherin/β-catenin During Epidermal Tumourigenesis in Dogs

Clinically relevant epidermal tumours in dogs include cutaneous papillomas (CPs) and cutaneous squamous cell carcinomas (CSCCs). The development of CPs and CSCCs involves dysregulation in expression of E-cadherin/β-catenin; however, knowledge about the contribution of these molecules to epidermal tumourigenesis in dogs is limited. This study examined the immunohistochemical expression pattern of E-cadherin/β-catenin in samples of normal canine epidermis, CPs, preneoplastic epidermis and CSCCs, using tissue microarrays, in order to elucidate whether the dysregulated expression of these molecules may contribute to the pathogenesis of clinically relevant epidermal tumours in dogs. We also investigated the correlation between the immunohistochemical expression pattern of E-cadherin/β-catenin in these tissue microarrays to further evaluate whether the disruption of the adherens junction interactions plays a relevant role in canine epidermal tumourigenesis. In samples of CP and preneoplastic epidermis, the membrane immunoreactivity of E-cadherin/β-catenin was conserved, while in CSCC, the immunoreactivity of these molecules was significantly reduced, independently of the tumour location. There was significant correlation between the membrane expression of E-cadherin/β-catenin in CSCC. β-catenin also showed cytoplasmic and nuclear expression in samples of CP, preneoplastic epidermis and CSCC. These results support the hypothesis that dysregulated expression of E-cadherin/β-catenin may play a critical role in the pathogenesis of relevant canine epidermal tumours, not only due to the disruption of the intercellular adherens junctions, but also due to the dysregulated activity of the signalling pathways in which these molecules are involved.

Malignant Transformation of a Canine Papillomavirus Type 1-Induced Persistent Oral Papilloma in a 3-Year-Old Dog

This case report describes a rare case of a persistent canine papillomavirus type 1 (CPV-1)-induced oral papilloma that underwent malignant transformation into an oral squamous cell carcinoma (OSCC) in a 3-year-old Labrador retriever cross. Initially, the patient had multiple and multifocal verrucous lesions populating the oral cavity exclusively. The papillomas persisted despite multiple surgical ablations, azithromycin, interferon α-2b, alternative medicines, and off-label drug use of an immunostimulant. After 1 year and 6 months, an aggressive lesion developed at the level of the left mandibular first molar (309) and progressed to a well-differentiated invasive OSCC. The presence of CPV-1 DNA in the OSCC, and the known oncogenic abilities of CPV-1, suggests that this virus might have played a significant role in the emergence of the OSCC that ultimately led to the patient's euthanasia due to poor quality of life. This is the first well-documented case where OSCC has developed from an oral papilloma caused by CPV-1 in which the presence of coinfection by another papillomavirus was excluded by multiple polymerase chain reaction tests using various primers.

Dysregulated expression of the key effectors of the mammalian target of rapamycin signalling pathway in cutaneous papillomas of dogs

Cutaneous papillomas (CP) are one of the most common skin neoplasms in dogs. Different murine models have shown that persistent activation of the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway has a central role in the development and progression of CP. The purpose of this study were to evaluate the immunohistochemical expression pattern of two key molecules involved in the PI3K/Akt/mTOR signalling pathway, pAkt^Ser473 , and pS6^Ser235/236 , on 36 canine specimens of CP using a tissue microarray. The results show that the PI3K/Akt/mTOR signalling pathway is persistently activated in CP of dogs, pointing to this pathway as a potential therapeutic target.

Type I interferons in the pathogenesis and treatment of canine diseases

Type I interferons (IFNs) such as IFN-α, IFN-β, IFN-ε, IFN-κ, and IFN-ω represent cytokines, which are deeply involved in the regulation and activation of innate and adaptive immune responses. They possess strong antiviral, antiproliferative, and immunomodulatory activities allowing their use in the therapy of different viral diseases, neoplasms, and immune-mediated disorders, respectively. Initially, treatment strategies were based on nonspecific inducers of type I IFNs, which were soon replaced by different recombinant proteins. Drugs with type I IFNs as active agents are currently used in the treatment of hepatitis B and C virus infection, lymphoma, myeloid leukemia, renal carcinoma, malignant melanoma, and multiple sclerosis in humans. In addition, recombinant feline IFN-ω has been approved for the treatment of canine parvovirus, feline leukemia virus, and feline immunodeficiency virus infections. However, the role of type I IFNs in the pathogenesis of canine diseases remains largely undetermined so far, even though some share pathogenic mechanisms and clinical features with their human counterparts. This review summarizes the present knowledge of type I IFNs and down-stream targets such as Mx and 2',5'-oligoadenylate synthetase proteins in the pathogenesis of infectious and immune-mediated canine diseases. Moreover, studies investigating the potential use of type I IFNs in the treatment of canine lymphomas, melanomas, sarcomas, and carcinomas, canine distemper virus, parvovirus, and papillomavirus infections as well as immune-mediated keratoconjunctivitis sicca and atopic dermatitis are presented. A separate chapter is dedicated to the therapeutic potential of IFN-λ, a type III IFN, in canine diseases. However, further future studies are still needed to unravel the exact functions of the different subtypes of type I IFNs and their target genes in healthy and diseased dogs and the full potential action of type I IFNs as treatment strategy.

Papillomaviruses in dogs and cats

Papillomaviruses (PVs) cause disease in both dogs and cats. In dogs, PVs are thought to cause oral papillomatosis, cutaneous papillomas and canine viral pigmented plaques, whereas PVs have been rarely associated with the development of oral and cutaneous squamous cell carcinomas in this species. In cats, PVs are currently thought to cause oral papillomas, feline viral plaques, Bowenoid in situ carcinomas and feline sarcoids. Furthermore, there is increasing evidence that PVs may also be a cause of cutaneous squamous cell carcinomas and basal cell carcinomas in cats. These diseases are discussed in this review. Additionally, there is a brief overview of PV biology, including how these viruses cause disease. Diagnostic techniques and possible methods to prevent PV infection are also discussed.

Canine autoimmune hemolytic anemia: management challenges

Immune-mediated hemolytic anemia is one of the most common manifestations of canine immune-mediated disease, yet treatment regimens remain nonstandardized and, in some cases, controversial. The main reason for this, as for most diseases in veterinary medicine, is the lack of large-scale placebo-controlled trials so that the efficacy of one treatment over another can be established. Most of the evidence used for treatment comes from retrospective studies and from personal preference and experience, and because of this, treatment regimens tend to vary among institutions and individual clinicians. Management of immune-mediated hemolytic anemia includes immunosuppression, thromboprophylaxis, and supportive care measures to help prevent and treat concurrent conditions.

Opportunistic fungal infections in dogs treated with ciclosporin and glucocorticoids: eight cases

Glucocorticoids are the standard of care for the treatment of immune-mediated disorders, and ciclosporin is increasingly being used off-label as an adjunct immunosuppressive drug in dogs. However, opportunistic infections can develop during combination immunosuppressive regimens. This case series describes atypical fungal infections in eight dogs treated with immunosuppressive dosages of glucocorticoids and ciclosporin. The median duration of combined treatment prior to the identification of fungal infection was 31 (range, 13 to 201) days, although two dogs received glucocorticoids for prolonged periods prior to the addition of ciclosporin. The estimated prevalence of serious fungal infections with this drug combination appears to be low (approximately 1 · 67%), but these infections led directly or indirectly to death or euthanasia in five of eight (63%) dogs. These cases highlight the need for frequent clinical monitoring of dogs receiving immunosuppressive dosages of glucocorticoids and ciclosporin.

Systemic fungal infection in a dog: a unique case in Ireland

A three year old male entire Staffordshire bull terrier was referred to University College Dublin Veterinary Hospital, with a two week history of fever, inflammation of the right hock, lameness on the right hindlimb, peripheral lymphadenopathy and gastrointestinal signs (vomiting and diarrhoea). For the preceding three months the dog had been treated for atopic dermatitis with oral ciclosporin (5 mg/kg, PO, q 24 hours).

Cytological analysis of the affected lymph nodes demonstrated fungal-like organisms predominantly contained within macrophages. Subsequent fungal culture and microscopic identification confirmed the presence of a Byssochlamys sp. This fungus is a saprophytic organism which has been associated with mycotoxin production. It has not previously been identified as a cause of systemic infection in animals or humans.

Ciclosporin was discontinued, and a second generation triazole, voriconazole prescribed at a dose of 6 mg/kg for the first two doses, and continued at 3 mg/kg every 12 hours for six months. There was an excellent response. Follow-up examination five weeks after treatment was completed confirmed remission of the disease. The dog remains alive and well three years later.

The present case represents an unusual fungal infection in a dog secondary to immunosuppressive therapy with ciclosporin. Such a possibility should be considered in animals presenting with signs consistent with systemic infection when receiving immunosuppressive medication.

Life-long diseases need life-long treatment: long-term safety of ciclosporin in canine atopic dermatitis

Ciclosporin (Atopica; Novartis Animal Health) has been licensed for canine atopic dermatitis (AD) since 2002. Adverse events (AEs) have been reported in 55 per cent of 759 dogs in 15 clinical trials, but are rare in pharmacovigilance data (71.81 AEs/million capsules sold). Gastrointestinal reactions were most common, but were mild and rarely required intervention. Other AEs were rare (≤1 per cent in clinical trials; <10/million capsules sold). Hirsutism, gingival hyperplasia and hyperplastic dermatitis were rarely significant and resolved on dose reduction. Ciclosporin decreases staphylococcal and Malassezia infections in AD, and at the recommended dose is not a risk factor for other infections, neoplasia, renal failure or hypertension. The impact on glucose and calcium metabolism is not clinically significant for normal dogs. Concomitant treatment with most drugs is safe. Effects on cytochrome P450 and MDR1 P-glycoprotein activity may elevate plasma ciclosporin concentrations, but short-term changes are not clinically significant. Monitoring of complete blood counts, urinalysis or ciclosporin levels is not justified except with higher than recommended doses and/or long-term concurrent immunosuppressive drugs. Ciclosporin is not a contraindication for killed (including rabies) vaccines, but the licensed recommendation is that live vaccination is avoided during treatment. In conclusion, ciclosporin has a positive risk-benefit profile for the long-term management of canine AD.

Oral cyclosporine treatment in dogs: a review of the literature

Cyclosporine is an immunomodulatory drug used to treat an increasing spectrum of diseases in dogs. Cyclosporine is a calcineurin inhibitor, ultimately exerting its inhibitory effects on T-lymphocytes by decreasing production of cytokines, such as interleukin-2. Although, in the United States, oral cyclosporine is approved in dogs only for treatment of atopic dermatitis, there are many other indications for its use. Cyclosporine is available in 2 oral formulations: the original oil-based formulation and the more commonly used ultramicronized emulsion that facilitates oral absorption. Ultramicronized cyclosporine is available as an approved animal product, and human proprietary and generic preparations are also available. Bioavailability of the different formulations in dogs is likely to vary among the preparations. Cyclosporine is associated with a large number of drug interactions that can also influence blood cyclosporine concentrations. Therapeutic drug monitoring (TDM) can be used to assist in attaining consistent plasma cyclosporine concentrations despite the effects of varying bioavailability and drug interactions. TDM can facilitate therapeutic success by guiding dose adjustments on an individualized basis, and is recommended in cases that do not respond to initial oral dosing, or during treatment of severe, life-threatening diseases for which a trial-and-error approach to dose adjustment is too risky. Pharmacodynamic assays that evaluate individual patient immune responses to cyclosporine can be used to augment information provided by TDM.

Cutaneous nocardiosis in two dogs receiving ciclosporin therapy for the management of canine atopic dermatitis

BACKGROUND

Ciclosporin is a calcineurin inhibitor that is currently registered for the treatment of canine atopic dermatitis. The most common adverse effects include mild, transient gastrointestinal disturbances. Single case reports of opportunistic infections due to Nocardia spp., Neospora spp. and papillomaviruses have also been reported.

HYPOTHESIS/OBJECTIVES

Clinicians should be aware of the potential risk of systemic immunosuppression and subsequent infection with Nocardia spp. in dogs receiving ciclosporin.

ANIMALS

Cutaneous nocardiosis in two dogs receiving ciclosporin therapy for management of canine atopic dermatitis.

METHODS

Histopathology, PCR for Nocardia spp. and computed tomography.

RESULTS

One dog developed disseminated nocardiosis due to Nocardia brasiliensis and a second dog developed localized cutaneous nocardiosis due to a novel Nocardia species subsequent to ciclosporin administration at the recommended dose rate for the management of canine atopic dermatitis. The second case was receiving a combination of ciclosporin and ketoconazole, and serum trough ciclosporin levels were elevated.

CONCLUSIONS AND CLINICAL IMPORTANCE

Clinicians should be aware of the potential risk of systemic immunosuppression and subsequent infection with Nocardia spp. in dogs receiving ciclosporin. Measurement of serum ciclosporin levels may be useful in identifying those individuals which are at risk of opportunistic infections.

Clinical, Histologic, and Computed Tomographic Features of Oral Papillary Squamous Cell Carcinoma in Dogs: 9 Cases (2008–2011)

Medical records of dogs diagnosed with oral papillary squamous cell carcinoma between December 2008 and April 2011 were reviewed. Information abstracted included signalment, tumor location, tumor size, computed tomographic (CT) features, evidence of metastatic disease based on cytologic examination of lymph node aspirates and thoracic radiography, treatment, surgical margins, histologic features, and treatment outcome. Dogs included in the study were all sexually altered, predominantly large breed dogs with a mean age of 3.9-years (range, 0.5 to 9.0-years). The most common location was the rostral maxilla. Invasion of underlying bone and lymphadenopathy were evident on CT imaging in most dogs. No evidence of metastasis was found on mandibular lymph node cytology and thoracic radiography. Histologic analysis revealed similar morphologic findings for all surgically resected tumors. Surgical excision with 1–2 cm margins was complete in all cases, with a mean tumor-free interval of 12.1-months.

Cyclosporine in veterinary dermatology

Cyclosporine is an immunomodulatory medication that is efficacious and approved for atopic dermatitis in dogs and allergic dermatitis in cats; it has also been used to successfully manage a variety of immune-mediated dermatoses in dogs and cats. This article reviews the use of cyclosporine in veterinary dermatology including its mechanism of action, pharmacokinetics, drug interactions, side effects, and relevant clinical updates. Dermatologic indications including atopic/allergic dermatitis, perianal fistulas, sebaceous adenitis, and other immune-mediated skin diseases are discussed.

Malignant transformation of a putative eyelid papilloma to squamous cell carcinoma in a dog

A 6-year-old female spayed Chihuahua was presented for the evaluation of generalized pigmented cutaneous masses, one of which was present on the lower right eyelid. The dog was not on immunosuppressive medications and did not have historical or laboratory evidence of underlying endocrine disease, including hypothyroidism and hyperadrenocorticism. Histopathology, immunohistochemistry, and polymerase chain reaction of a cutaneous biopsy from the left antebrachium containing representative lesions confirmed viral papillomatosis. Additionally, histopathology of the antebrachial mass revealed regions of epithelial dysplasia suggestive of possible early transformation to malignancy. Over the course of 5 months, the mass on the right lower eyelid progressed to encompass and efface the majority of the eyelid margin. Additionally, the eyelid tumor had changed from an ovoid, brown pigmented mass to an irregular, flesh-colored mass. At the dog's last recheck examination, a corneal ulcer had developed beneath the irregular dorsal margin of the tumor. Histopathology of the eyelid mass was consistent with squamous cell carcinoma (SCC) and was positive for the presence of papillomavirus using polymerase chain reaction. This report describes the transformation of a putative viral eyelid papilloma into a malignant SCC in an adult dog.

Papillomavirus-Associated Cutaneous Neoplasia in Mammals

For humans, strong evidence indicates that some mucosal papillomavirus (PV) types cause genital and oral neoplasia, and weaker evidence suggests that some cutaneous PVs may cause cutaneous squamous cell carcinomas (SCC). For nonhuman species, strong evidence supports a causal role of PVs in the development of feline and equine sarcoids. Likewise, PVs are believed to cause cutaneous SCCs in rabbits, western barred bandicoots, and some rodents. Furthermore, some evidence suggests that PVs may influence the development of both feline and canine cutaneous SCCs. This review discusses the evidence that PVs cause human cutaneous SCCs and the proposed mechanisms for this action. It then reviews preneoplastic and neoplastic skin diseases that are associated with PV infection in nonhuman mammals.

Masitinib for the treatment of canine atopic dermatitis: a pilot study

There is an on-going need to identify medications suitable for the long-term treatment of canine atopic dermatitis (CAD). Masitinib mesilate is a potent and selective tyrosine kinase inhibitor of the c-KIT receptor. A strong relationship exists between the SCF/c-KIT pathway and pathogenesis of CAD, suggesting that masitinib may potentially fulfil the above role. This study reports on an uncontrolled pilot study of masitinib in CAD. Masitinib was administered orally to 11 dogs at a mean dose of 11.0 +/- 1.83 mg/kg/day (free base) for 28 days. Treatment response was assessed by evolution of clinical appearance according to a modified version of the Canine Atopic Dermatitis Extent and Severity Index (mCADESI), pruritus scale and surface area of lesions. Masitinib improved CAD with a mean reduction in mCADESI of 50.7 +/- 29.8% (95% C.I. = 29.4-72.0; p = 0.0004) at day 28 relative to baseline, with 8/10, 8/10 and 4/10 dogs showing improvement of >or=33%, >or=40% and >or=50%, respectively. Improvement was further evidenced by a decrease in pruritus score and the surface area of lesions. No serious or severe adverse events occurred during this trial, although 6/11 dogs presented with mild to moderate treatment related adverse events. There is sufficient compelling evidence to warrant further investigation.

Detection of antibodies against epidermodysplasia verruciformis-associated canine papillomavirus 3 in sera of dogs from Europe and Africa by enzyme-linked immunosorbent assay

The role of papillomaviruses (PVs) in the development of canine cancers is controversial. However, recently a novel canine PV (CPV3) was detected in a dog affected with a condition reminiscent of epidermodysplasia verruciformis (EV). The aim of the present study was to investigate the seroprevalence of CPV3 by using generic enzyme-linked immunosorbent assays (ELISAs) for the detection of antibodies against either canine oral PV (COPV) or CPV3. Therefore, the capsid proteins of both PV types were expressed as glutathione S-transferase fusion protein antigens and adsorbed to glutathione-casein-coated ELISA plates. After showing that PV type-specific antibodies could be detected in the sera from dogs with confirmed COPV or CPV3 infection, CPV3- and COPV-seropositive samples were detected in two sets of canine sera collected in Switzerland and South Africa, respectively. We found specific antibodies against COPV and CPV3 among the tested sera and also a large number that were positive for both antigens. The seroprevalences of PV antibodies of 21.9% (COPV) and 26.9% (CPV3) among the tested dogs from South Africa were higher than those among the dogs from Switzerland at 10.5% (COPV) and 1.3% (CPV3). Our data suggest a need for further CPV-related seroepidemiological surveys in different countries, especially in the context of clinical manifestations and possible breed predispositions. For this purpose, the newly developed ELISAs can be a useful tool.

Granulocytopenia Associated With Thymoma in a Domestic Shorthaired Cat

A 5-year-old, spayed female cat was referred because of a mass in the cranial mediastinum noted on thoracic radiographs. A thymoma was diagnosed following ultrasound and biopsy of the mass. Treatment was initiated with coarse-fraction radiation therapy using external-beam therapy (four fractions of 5 Gy). The mass responded, but granulocytopenia developed. Bone marrow examination showed a myeloid to erythroid ratio of approximately 1:1, with a left shift within the myeloid line. These findings, as well as the lack of toxic changes within the peripheral blood neutrophils, suggested immune-mediated destruction of peripheral granulocytes. Immune suppression with prednisone and cyclosporine was instituted. After 7 weeks, the neutrophil count returned to normal. The tumor was removed, and cyclosporine was reduced and eventually discontinued 3 weeks postsurgery.

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.