Outcome of a bilateral mastectomy in a Criollo mare with adenocarcinoma - case reportABSTRACT
Mammary neoplasms are rare in horses compared to other species. However, early diagnosis is crucial to ensure adequate treatment and complete recovery. This study presents a detailed case report of a Criollo mare diagnosed with unilateral mammary adenocarcinoma. It emphasizes the importance of a multidisciplinary approach and personalized treatment plans in achieving a successful outcome and ensuring a high quality of life for the mare. Histopathological analysis was vital for confirming the definitive diagnosis. The therapeutic approach involved a total mastectomy, including the removal of inguinal lymph nodes and a safety margin. Because the surgical procedure resulted in a significant skin defect, the treatment strategy incorporated various therapies, such as the use of amniotic membrane, daily cleaning, and the application of crystal sugar, all in combination with appropriate pharmacological therapy. Despite the rarity of this type of neoplasm in horses, this case report highlights the significance of early diagnosis and tailored therapeutic interventions. It also provides valuable insights into the clinical management and treatment of mammary neoplasms in horses.
Keywords:
mammary gland; neoplasm; amniotic membrane; histopathology
RESUMO
A ocorrência de neoplasias mamárias em equinos é baixa quando comparada com outras espécies, entretanto o diagnóstico precoce é importante para que o tratamento seja adequado e permita a recuperação plena no paciente. O presente estudo descreve de forma detalhada o relato de caso de uma égua da raça Crioula diagnosticada com adenocarcinoma mamário unilateral. A integração de uma equipe multidisciplinar e a individualização do tratamento foram destacadas como aspectos essenciais para garantir a recuperação bem-sucedida da égua e a sua qualidade de vida. O diagnóstico histopatológico foi crucial para determinar o diagnóstico definitivo. A abordagem terapêutica incluiu a realização de mastectomia total, com remoção de linfonodos inguinais e margem de segurança. Devido à grande extensão do defeito cutâneo posterior ao procedimento, o tratamento foi realizado com o uso de terapias associadas, incluindo o uso de membrana amniótica, limpeza diária e uso de açúcar cristal, atuando em sinergismo com a terapia farmacológica adequada. Ressalta-se a importância do diagnóstico precoce e da abordagem terapêutica adequada, apesar da raridade desse tipo de neoplasia em equinos. Este relato de caso oferece insights valiosos para a compreensão e o manejo clínico de neoplasias mamárias em equinos.
Palavras-chave:
glândula mamária; neoplasia; membrana amniótica; histopatologia
INTRODUCTION
The mammary gland in female horses is located in the inguinal region, consisting of two sections divided by a connective tissue septum, with each part containing a glandular body and a teat (Hughes, 2021). The glandular portion is subdivided into caudal and cranial lobes, and each teat typically has two openings (Hughes, 2021).
Mammary neoplasms in mares are relatively rare compared to other species (Mocholi et al., 2016), with a higher incidence among females aged 12 to 25 years (Knottenbelt, 2003). They are generally malignant and locally aggressive (Shank, 2009; Sabiza et al., 2020). The most recommended treatment is surgical excision (Prendergast et al., 1999). However, given the low frequency of mammary neoplasms in horses, establishing a consistent treatment approach can be challenging (Beggan et al., 2023). In rural settings, surgical and postoperative support can be limited (Shank, 2009), necessitating a hospital-level approach.
Due to the limited records of equine mammary tumors, detailed case reports are essential for aggregating data for epidemiological evaluation (Hughes, 2021). The objective of this study is to report a case of mammary gland adenocarcinoma in a Criollo mare, detailing the surgical treatment via total mastectomy, highlighting the importance of accurate histopathological diagnosis, and emphasizing the need for meticulous surgical and postoperative care to ensure animal survival and proper recovery.
CASE REPORT
A 19-year-old Criollo mare, weighing 440 kg, was referred to the Veterinary Clinic Hospital at the Federal University of Pelotas (HCV-UFPel) for clinical evaluation and surgical removal of a lesion. The mare had a history of an ulcerative lesion with increased volume and progressive growth in the ventral region of the right udder, which began six months prior to her hospital admission. During this period, systemic treatment with penicillin and streptomycin was administered, along with seven days of area cleaning, but no other interventions were performed before hospital referral.
Upon initial examination, a physical inspection of the animal, general clinical examination, blood count, and serum biochemistry were performed. An inspection revealed an ulcerated granulomatous lesion in the ventral region of the right udder with myiasis of varying degrees, while the left udder showed no signs of lesions (Fig. 1). The clinical examination showed no abnormalities in vital signs. The blood count indicated leukocytosis (16,600 cells/µL) with neutrophilia (12,284 cells/µL), hyperfibrinogenemia (800mg/dL), a hematocrit of 25%, and total plasma protein of 8.4g/dL. The serum biochemical test indicated urea at 39mg/dL and gamma-glutamyltransferase (GGT) at 15.8 IU/L.
A) Visual inspection of the lesion in the mammary gland with the animal in a standing position, taken on the day of arrival at HCV-UFPel. B) Visual inspection of the lesion with the animal in dorsal recumbency.
Considering the clinical condition and lesion extent, a total mastectomy was performed, including the contralateral mammary gland, following the technique described by Sysel and Moll (1999), with a 5cm safety margin. The removed tissue weighed 13.35kg, measuring 35 x 30 x 25cm, and fragments were sent for histopathological analysis (Fig. 2). Due to the large tumor mass, complete wound closure was not possible. Therefore, amniotic membrane, previously treated in glycerin, was used to promote healing and tissue recovery (Fig. 3).
Macroscopic view of the tumor mass from the mammary gland after removal via bilateral mastectomy. Arrow: left udder showing no visible macroscopic abnormalities.
Amniotic membrane covering the skin lesion following bilateral mastectomy in a mare, used to induce healing by secondary intention. Note the suture in the cranial portion, joining the skin edges for healing by primary intention.
Postoperative therapy included sulfamethoxazole with trimethoprim (15mg/kg orally) for nine days, flunixin meglumine (1.1mg/kg intravenously) for five days, and omeprazole (20g orally) for 10 days. Dipyrone (25mg/kg intravenously) was administered as needed. The amniotic membrane was removed six days after surgery, and reapplication was deemed unnecessary. After membrane removal, the wound was cleaned with 2% chlorhexidine and saline solution. The ventral abdomen was massaged using a pressure water shower to address edema in the region.
Histopathological analysis of the excised tissue revealed adenocarcinoma with indications of vascular invasion. Among the neoplastic cells, there were focally extensive areas of necrosis. Additionally, a densely cellular, non-encapsulated, non-delimited, and invasive neoplastic proliferation was detected. Atypia and pleomorphism were mild, whereas anisokaryosis was moderate. In 10 high-magnification fields (400x), 24 mitotic figures were observed.
Fifteen days after the surgery, an ultrasound examination of the surgical site showed subcutaneous edema and the presence of dead space. Therefore, daily cleaning continued, and crystal sugar was applied to the affected area. During this period, a follow-up blood count and serum biochemical tests were conducted, which did not reveal any alterations. After two months of hospitalization, the animal was discharged, having shown significant improvement and healing consistent with the expected postoperative timeframe. Daily wound care was recommended at the original location of the animal until full recovery.
DISCUSSION
Upon evaluation at HCV-UFPel, a significant increase in volume consistent with tumor growth was observed in the right mammary gland of the mare. The appearance of the lesion suggested considerable tumor progression, likely due to the lack of definitive diagnosis and appropriate early treatment. Thus, surgical intervention not only facilitated a definitive diagnosis but also served as an initial therapeutic approach.
Diagnosing mammary neoplasia in mares requires a multimodal approach (Shank, 2009; Beggan et al., 2023), with histopathological examination being the key to confirming the definitive diagnosis (Shank, 2009). In this case, the histopathological analysis identified mammary gland adenocarcinoma, defined as a malignant tumor arising from secretory epithelial glandular cells. Notable microscopic features of tumor malignancy (Shank, 2009), such as a high mitotic rate, cellular atypia, necrosis, and areas of cellular invasion, were observed in the sample.
The surgical treatment of choice was bilateral mastectomy, a procedure commonly recommended for mammary gland tumors (Shank, 2009; Ferreira Junior et al., 2019). The tendency of adenocarcinoma to metastasize to inguinal lymph nodes, other organs, and contralateral mammary glands (Knottenbelt, 2003) supported the decision to pursue this approach. The removal of lymph nodes during the procedure was considered the most challenging step due to tissue disorganization and the extent of tissue removal required. However, the expertise of the surgical team and thorough preparation ensured the success of this procedure.
As a result of the size of the adenocarcinoma and the extent of the surgical intervention, a large area was removed, leading to considerable tissue loss requiring specialized care for recovery and healing. Common complications with this type of surgical approach include challenges with first-intention healing, formation of dead space with fluid accumulation, and difficulty in applying local bandages (Shank, 2009; Ferreira Junior et al., 2019). To mitigate these issues, an amniotic membrane was initially used to cover the post-surgical lesion due to its elasticity, collagen and protein-rich composition, granulation tissue suppression, low antigenicity, and strong adhesive properties (Bigbie et al., 1990). Upon removal of the membrane, the lesion displayed uniform granulation tissue, regular scar edges around the entire wound, and an absence of secretion, indicating that the use of the amniotic membrane was effective during the initial healing phase. However, ultrasound examination 15 days after surgery revealed dead space, prompting the use of crystal sugar in the wound management protocol to stimulate the granulation process, modulate inflammation, and provide antibacterial effects through hyperosmolarity (Moreira et al., 2009). This approach yielded successful results with healing by secondary intention.
The pharmacological therapy for this case focused on improving the post-operative recovery of the mare and ensuring her well-being. For post-surgical analgesia in horses, non-steroidal anti-inflammatory drugs (NSAIDs) are the preferred option, which can be associated with opioids, ketamine, and systemic lidocaine when more potent analgesia is needed (Mocholi et al., 2016). In this case, NSAIDs alone were sufficient to achieve satisfactory analgesia and well-being, indicated by the absence of pain, the alert consciousness of the mare, interactions with observers and the environment, and stable vital functions throughout the treatment period.
This case reinforces the importance of an integrated and individualized approach to treating mammary adenocarcinoma in horses, focusing not only on survival but also on preserving the quality of life. Mammary adenocarcinoma in horses poses a clinical challenge due to its low incidence and rapid progression when not diagnosed and treated early. The multidisciplinary approach, covering everything from definitive diagnosis to surgical treatment and post-operative care, plays a key role in achieving satisfactory outcomes.
CONCLUSIONS
Mammary adenocarcinoma is an uncommon condition in horses but can have catastrophic consequences for mammary gland function and the health of the mare. The challenge posed by a large and rapidly growing neoplasm requires an adequate and accurate diagnosis, along with meticulous surgical and post-operative care, to ensure the recovery of the animal. Despite the loss of a critical organ, the treatment protocol used in this case led to a full recovery and allowed the mare to maintain her quality of life.
REFERENCES
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Publication Dates
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Publication in this collection
21 Feb 2025 -
Date of issue
Mar-Apr 2025
History
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Received
04 June 2024 -
Accepted
19 Sept 2024
