Identification of canine transmissible venereal tumor cells in the colostrum of a bitch - case report

[Identificação de células de tumor venéreo transmissível no colostro de uma cadela - relato de caso]

ABSTRACT

Canine Transmissible Venereal Tumor (cTVT) is a contagious tumor in dogs. Commonly, it develops in the sexual organs including the potential to metastasize to the mammary gland. This report describes cTVT cells in the colostrum of a pregnant bitch with metastasis in the mammary gland. A three-year-old Dalmatian bitch was pregnant and presented nodules on the vagina dorsal floor and on the right cranial abdominal and left cranial abdominal mammary glands. Cytology of the nodules and the colostrum were performed. Cytological analysis identified cells from the cTVT, subtype plasmocyte cells (TVTcP). It was recommended to avoid breastfeeding of newborns because of the possibility of transmission to them, since cTVT is an easily transmissible tumor. The bitch was monitored to start the standard treatment for cTVT based on chemotherapy.

Keywords:
milk; mammary gland; neonate; round cell tumor

RESUMO

O tumor venéreo transmissível (TVT) é um tumor contagioso em cães. Comumente, ele se desenvolve nos órgãos sexuais, com potencial de metastatizar para a glândula mamária. Este relato descreve células de TVTc no colostro de uma cadela prenhe com metástase na glândula mamária. Uma cadela dálmata, de três anos, estava prenhe e apresentou nódulos no assoalho dorsal da vagina e nas glândulas mamárias abdominais craniais direita e abdominais craniais esquerda. Foi realizada citologia dos nódulos e do colostro. A análise citológica identificou células do TVTc, células plasmocitárias subtipo (TVC cP). Foi recomendado evitar a amamentação dos recém-nascidos devido à possibilidade de transmissão, uma vez que o TVTc é um tumor facilmente transmissível. A cadela foi monitorada para iniciar o tratamento padrão para TVTc baseado em quimioterapia.

Palavras-chave:
leite; glândula mamária; neonatos; neoplasias de células redondas

INTRODUCTION

The Canine Transmissible Venereal Tumor (cTVT) is a transmittable tumor of round cells that occurs frequently in stray dogs. In most cases, the transmission is venereal and they tend to occur around the genitals. However, it can be seen in other areas by the contact of the tumor cells with mucous membranes of the nose, the mouth and the eye (Pimentel et al., 2021).

The cTVT can also invade other tissues through metastasis, such as organs of the abdominal cavity (Binli et al., 2021), brain, skin, eye, spine, breast tissue and lymph node (Pimentel et al., 2021). The most frequent genitals findings are variable-sized, friable, bleeding masses with the appearance of "cauliflower head” seen in the vagina, vulva or penis (Uçar, 2016).

The diagnosis of cTVT is confirmed by observation of the typical tumor cells in the cytologic and histopathologic examination. The cTVT can be classified as lymphocytoid, plasmacytoid and mixed, according to the cytomorphological criteria observed (Ante et al., 2021). The plasmacytoid subtype has been shown to be the most common and the most severe, with a higher risk of metastasis when compared to the others (Valençola et al., 2015). In addition, it is reported to be more resistant to chemotherapy (Ante et al., 2021).

The metastasis of cTVT in the mammary gland are still poorly described and until now there are no reports of tumor cells found in the colostrum of bitches when they are pregnant. Thus, the purpose of this study was to report a case of cTVT metastasis to the mammary gland with identification of tumor cells in colostrum.

CASE REPORT

A three-year-old, Dalmatian bitch, 18 kg, non-spayed was admitted showing a history of five months of vulvar bloody discharge. The patient had free access to the street, and it was pregnant at the time of the clinical evaluation.

At the general physical examination, the patient was in good body condition and showed no changes in the physiologic parameters.

At the reproductive system evaluation, it was observed a reddish, irregular, friable, bloody mass measuring 4.8 x 7.5 x 3.4cm, located on the vagina dorsal floor. The nodules in the mammary glands were soft, irregular, rounded shape and mobile. The nodule in the right cranial abdominal measured 2.5 x 1x 1cm and in the left cranial abdominal 0.3 x 0.2 x 0.1cm (Fig. 1). On the palpation of the mammary glands, it was noted in all mammary glands a thick, sticky and yellowish discharge featured as colostrum, except in the cranial and caudal thoracic ones.

Figure 1
Macroscopic appearance of nodules in the right and left cranial abdominal mammary glands of a bitch with metastatic transmissible venereal tumor (red circle).

Further examinations were performed to rule out systemic abnormalities. Blood samples were submitted for blood count, biochemistry analysis (no changes were seen) and rapid immunochromatographic test 4DX - IDDEXX. This test result showed positivity for Ehrlichia canis/ewingii. Thoracic radiographs in projections (right and left lateral and ventrodorsal) were performed and no significant abnormalities were observed. Abdominal ultrasonography examination confirmed pregnancy (gestational age near 56 days) that could allow surgery due to the beginning of fetal distress.

Cytology (by capillarity) of the vaginal nodules and of the nodules in the right and left cranial abdominal mammary gland, as well as the imprint of the colostrum discharge of all the mammary glands (Fig. 2), were collected. Cytological analysis of all nodules and of the colostrum confirmed the presence of cTVT tumor cells, plasmacytoid subtype (cP TVT) (Fig. 3).

Figure 2
Cytology imprint and macroscopic appearance of the colostrum in the right cranial abdominal mammary gland of a bitch with metastatic cTVT.

Figure 3
Numerous round cells showing eccentric nucleus with discretely coarse chromatin, evident and multiple nucleoli, distinct basophilic cytoplasm, broad and moderately vacuolar (red arrow). Discrete anisocytosis and moderate anisokariosis.

Considering all these facts, surgery was indicated to avoid the passage of the puppies thorough the vaginal area during a normal birth due to the presence of the tumor. Additionally, to avoid the possibility of transmission of cTVT to the puppies, it was recommended that the nursing of the puppies should be avoided, and artificial feeding would be prescribed. Also, it was advised that the patient should return for clinical monitoring and to start chemotherapy.

DISCUSSION

The genital presentation of cTVT is well-documented and it is common in several areas of Brazil where a large number of dogs have free access to the street, and they are usually non-spayed (Pimentel et al., 2021). Our data agree with the description above since the patient came from an area where there are many stray dogs. The cTVT diagnosed in this study was of the plasmacytoid type which has been shown to be the most frequently related to metastasis (Valençola et al., 2015). In this case report, the same features that agreed with the previous authors were described.

It is known that the extragenital spread of the cTVT can occur for a variety of tissues, however, considering the involvement of the mammary gland tissue, there are few reports describing these alterations (Chikweto et al., 2013), and showing the relevance of the cytological analysis in mammary alterations of bitches epidemiologically susceptible to develop this tumor.

Two cases of genital cTVT with mammary gland metastasis of non-pregnant bitches have already been reported (Horta et al., 2014) They have also observed the presence of vaginal cTVT with cutaneous metastasis in the mammary gland, near the nipples of a non-pregnant bitch (Varughese et al., 2012). In this study, the unpublished data is the fact the patient was pregnant, close to giving birth, leading the clinicians to think on the possibility of neonatal mechanical transmission, in this case, by colostrum.

Although it is increasingly common, the metastatic behavior of this tumor is still not clear. One of the theories is that its dissemination occurs in immunosuppressed animals (Küçükbekir et al., 2021), as well as the patient of this study. It should be highlighted that at the time of the appointment, the patient showed positivity for Erlichiosis, and it was pregnant. Considering these facts, the patient was probably naturally immunosuppressed (Castro et al., 2022; Ahmed et al., 2023) and was exposed to the tumor maintenance and dissemination. In addition, it is described that tumor masses with chronic behavior also predispose to metastasis, as previously reported (Horta et al., 2014). Our data agreed with the mentioned authors since the patient had been presenting the genital mass for more than five months.

Until now, there were no published data describing cP TVT tumor cells in the colostrum of bitches with metastasis in the mammary gland. This case report contributes to developing new hypotheses and research considering cTVT. For example, the possibility of tumor development by neonates when they ingest the colostrum. Since it is an easily transmittable tumor, it might develop in the mouth of the animals due to the nursing or even in any part of the digestive tract of these animals.

In this report, the diagnosis of cTVT was performed through the anamnesis, the tumor characteristics and the cytologic evaluation, an important diagnostic tool, especially for round cell tumors, such as cTVT (Pimentel et al., 2021). The cytologist assisted the clinician enabling the detection of tumor cells in the colostrum and with the reflection on what clinical decision should be made in the case of a pregnant bitch in her final trimester showing metastatic cTVT it the mammary gland.

In addition, the present report highlights the need to perform the cytologic examination as a diagnosis tool for masses located in extragenital sites in dogs from areas where this tumor presents high incidence (Cassali et al., 2020).

The evidence that cTVT cells can be transmitted through the colostrum of pregnant bitches with metastasis in the mammary gland warns to the possibility of tumor development by neonates when they ingest colostrum, since it is considered a tumor of easy transplantation. Therefore, it should be highlighted the need for further studies to better understand the biological behavior of this tumor and the different ways of transmission of cTVT, especially in endemic regions.

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Publication Dates

• Publication in this collection
  28 Apr 2025
• Date of issue
  May-Jun 2025

History

• Received
  11 Sept 2024
• Accepted
  28 Oct 2024