Journal of Veterinary Science & Medical Diagnosis ISSN: 2325-9590

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Case Report, J Vet Sci Med Diagn Vol: 4 Issue: 1

Unusual Presentation of Extra- Genital Canine Transmissible Venereal Tumor in an Adult Cross-Breed Dog Palatine and Rectal Lesions without Primary Genital Lesions

King Shimumbo Nalubamba*
University of Zambia, School of Veterinary Medicine, Clinical Studies Department, Zambia
Corresponding author : King Shimumbo Nalubamba
University of Zambia, School of Veterinary Medicine, Clinical Studies Department, P O Box 32379, Lusaka 10101, Zambia
Tel: 00260977848947; Fax: 00260211293727
E-mail: [email protected]
Received: February 27, 2014 Accepted: July 18, 2014 Published: July 22, 2014
Citation: Nalubamba KS (2015) Unusual Presentation of Extra-Genital Canine Transmissible Venereal Tumor in an Adult Cross-Breed Dog – Palatine and Rectal Lesions without Primary Genital Lesions. J Vet Sci Med Diagn 4:1. doi:10.4172/2325-9590.1000149

Abstract

Unusual Presentation of Extra-Genital Canine Transmissible Venereal Tumor in an Adult Cross- Breed Dog – Palatine and Rectal Lesions without Primary Genital Lesions

Canine transmissible venereal tumor (CTVT) is a tumor that occurs commonly in young, sexually active, free-roaming dog populations in developing countries. It commonly affects the external genitalia in both male and female dogs and rarely metastasises. This case report documents an unusual presentation of concurrent oral-palantine and rectal CTVT in an adult male dog with no primary genital lesions. Diagnosis of the CTVT was confirmed by cytological examination of fine needle aspirate smears that revealed CTVT cells that were classified as mixed, based on cytomorphological characteristics. This case report documents concurrent CTVT lesion in two unusual locations. A successful case outcome leading to complete regression of both extra-genital CTVT lesions, without relapse one year after chemotherapy with vincristine sulphate is also recorded.

Keywords: Canine; Dog; Extra genital canine transmissible venereal tumor (CTVT); Zambia

Keywords

Canine; Dog; Extra genital canine transmissible venereal tumor (CTVT); Zambia

Introduction

Canine transmissible venereal tumor (CTVT) is a relatively common tumor in young, sexually active, free-roaming dog populations. It commonly affects the mucosa of the penis and vagina and is usually transmitted via coitus. Transmission may also occur through mucosal contact with neoplastic cells, biting, licking, scratching, and sniffing lesions. CTVT is a naturally occurring allograft that has only 59 chromosomes compared to the canine host’s 78 chromosomes. Generally, the disease affects sexually mature dogs between two and eight years-old and mainly females. There is no breed predilection [1,2]. It has been assumed that CTVTs have a histiocytic origin [3]. Canine transmissible venereal tumors may be classified based on cytomorphological characteristics as lymphocytic, plasmacytic or mixed [4].
Metastases of CTVT from primary genital foci to extra-genital sites, though rare, have been described, including metastasis without primary genital lesions [5,6]. Severe forms of CTVT with haematogenous circulating neoplastic cells have also been reported in immunocompromised canine hosts [7]. Spontaneous regression of CTVT lesions occurs in immunocompetent hosts and tumors that have been present for less than nine months [1]. Treatment involves surgical excision of CTVT masses, chemotherapy, immunotherapy or combinations of aforementioned. Chemotherapy alone is the preferred treatment method in Africa, although Mukaratirwa et. al., reported that chemotherapy with vincristine sulphate combined with intralesional BCG injections led to faster regression of the CTVT lesions [1].
The current case report documents, an unusual clinical presentation of extra-genital CTVT (with an oral mass as well as a rectal mass) and its successful treatment with a single chemotherapeutic agent, namely; five, once-a-week intravenous vincristine sulphate injections.

Case Report

A four and a half-year-old, intact male cross-bred pet dog was presented to a private veterinary practice in Lusaka, Zambia with a history of progressive ‘choking,’ mild halitosis and occasional bloodtinged salivation, three weeks prior to presentation. The dog was reported to be predominantly confined, but would occasionally leave the yard. The dog was fed a commercial dry diet and supplemented with human food scraps. Owners suspected that the dog had swallowed a foreign body such as a bone.
Clinical examination revealed a bright and active patient with normal vital parameters. The dog was in good physical condition with no lymphadenopathy. Oral examination revealed two adjacent reddish masses in the distal oropharynx region. There was no history of the dog having any other masses in the past and the owners were thus, not sure when or how the lesions started.
Palpation and visual examination of the penile and preputial mucosae did not reveal any abnormalities. Digital rectal examination revealed a mildly enlarge prostate as well as an approximate 2.0 cm x 1.5 cm, red, ulcerated, cauliflower-like mass in the distal rectum that could be visualized by eversion of the rectal mucosa. The mass was firmly adherent to the rectal mucosa.
Blood was collected via cephalic vein venipuncture for a complete blood count and revealed a normal haemogram within the reference values.
Survey thoracic and abdominal radiographs were taken to check for metastasis and were unremarkable.
The dog was anaesthetized with intramuscular xylazine (Xylaject® 2%, Dopharma, The Netherlands) at 2mg/Kg body weight and ketamine (Sanket® 10%, Dopharma, The Netherlands) at 15mg/Kg body weight. Further detailed oral examination showed a large pedunculated, ulcerated, smooth-surfaced reddish mass and a smaller one on the proximal left side of the soft palate measuring approximately 5.0 x 4.0 cm and 2.5 x 1.5 cm respectively (Figure 1). Fine needle aspiration of the oral and rectal masses was carried out for cytology whilst the patient was still anaesthetised.
Figure 1: Photograph of the large and smaller palatine canine transmissible venereal tumor masses in the open mouth of the patient. Lower right part of the picture showing an endotracheal tube.
Cytological examination of air-dried, Giemsa-stained smears of the fine needle aspirates of the oral and rectal masses revealed discrete round/ovoid cells of variable sizes. The cells presented a slight basophilic cystoplasm with several; punctate clear vacuoles. Nuclei were central or eccentric, large, round, with coarse nuclear chromatic (Figure 2). The CTVT was classified as mixed based on the enumeration and cytomorphological classification criteria by Flórez et al. [4].
Figure 2: Photograph of the fine needle aspirate cytology of canine transmissible venereal tumor (CTVT) smear stained with Giemsa (x 1000) showing CTVT cells of various shapes characterized with rounded nuclei and vacuolated cytoplasm and a few erythrocytes and neutrophils
The case was managed with five, once-weekly intravenous vincristine sulphate injections at 0.025 mg/kg body weight. Marked regression of the masses was observed within one week at the second treatment and complete regression of the palantine mass was seen at the fourth treatment whilst the rectal one was still minimally palpable. The rectal mass was no longer palpable at the fifth treatment and thus, the chemotherapy was discontinued. Complete blood examination was done weekly to monitor haematological changes and no serious untoward sequela other than mild anorexia that was reported after the third treatment. The mild anorexia was treated with daily oral multivitamin tablets until one week after the end of the chemotherapy.
The dog was castrated three months after the end of the chemotherapy to reduce the risk of the dog contracting genital CTVT. One year after initial presentation and successful chemotherapy, the dog was still in good health with no recurrence of the CTVT reported.

Discussion

To the author’s knowledge, this is the first case of concurrent extragenital rectal and palantine CTVT without primary genital lesions in literature although a single case of palantine CTVT is recorded by Bright et al. [6]. Other differential diagnosis to this case could have been amelanotic melanomas, lymphomas, squamous cell carcinomas, rectal polyps; but cytological findings from the fine needle aspirate and response to treatment ruled them out.
The palantine CTVT mass was ulcerated in certain areas but it was not infected. It not being infected was not unusual as CTVT masses have been shown not to be particularly prone to infection [8]. Only mild halitosis was present in this case despite such a large CTVT mass in the oropharyngeal region. The intermittent mechanical trapping of food by the mass in the mouth and resultant superficial bacterial proliferation there could have been the reason for the mild halitosis observed.
The author can only hypothesise that the lesion must have arisen from biting a CTVT from an infected dog, probably due to a dog fight or other social interaction. It is also possible that the oral and the rectal lesions could have been primary or secondary lesions based on dogs’ behaviour of licking its own anus. Further, the rectal lesion could have been the result of inappropriate sexual mounting that has been shown between male dogs. There is also the possibility that the two masses were unrelated. The author however, cannot rule out the possibility that, the case could have had a primary genital lesion that had regressed and the metastatic extra-genital lesions were regressing more slowly, since some authors insist that no extra-genital lesions can occur without primary genital lesions [9]. However, the fact that this case did not have a primary genital lesions is similar to findings by a number of researchers [3,5].
The oral masses could have been made atypically smooth rather than the irregular, cauliflower-like presentation that is characteristic of CTVT lesions due to the daily, regular passage of foodstuff that could have continually eroded the villi and smoothened the tumour surfaces.
Blood tinged saliva was only reported to have been present intermittently. This could have been due to the dog swallowing the blood arising from the excoriating CTVT lesion. Mild to moderate melaena would have been expected if copious amounts of blood were swallowed from the oral CTVT lesions. However, it was not reported in this case nor was it seen during the rectal digital examination.
The patient did not demonstrate superficial palpable lymphadenopathy, not even of the submandibular lymph nodes that drain the head region where the larger CTVT lesions were. Although radiographs were done to check for overt internal lymphadenopathy or organomegaly and did not reveal any; abdominal ultrasonographic examination would have yielded better and more detailed information on possible abdominal metastasis on an organ by organ basis. This would have added great value to the case’s diagnostic work-up quality. Unfortunately, it was not carried out due to the high cost, and inability of the owner to meet that cost.
The patient only became mildly anorectic after the third vincristine sulphate injection and this was successfully managed by oral multivitamin tablets (VitaDOG®, Biotech. Tanzania) only. It did not result in significant weight loss of the patient at the completion of therapy. Anorexia, as a complication of vincristine therapy, is reported [1]. No recurrence of the CTVT lesions was reported in this dog one year after initial presentation. This is considered a normal outcome of a successful treatment of non-refractory CTVT, since the development of transplantation immunity is the normal outcome in immunocompetent hosts. Although the dog was castrated to prevent it from contracting genital CTVT, castration may not completely eliminate the risk of the dog contracting extra-genital CTVT that may occur from non-sexual related socializing behaviour.

Conclusion

An unusual clinical presentation of CTVT has been described and this is important mainly to their direct relationship with other differential diagnosis. Moreover, this case demonstrates that chemotherapy alone can be highly efficient even in extra-genital CTVT.

Conflict of Interest

The author declares that there is no conflict of interest regarding the publication of this article.

Acknowledgments

Mr. A Banda for assisting in the case management while the dog was under treatment.

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