Mammary Mastectomy Due to Mammary Gland Tumors in Intact Female Dog

follow-up. Surgical correction of mammary tumors in a female dog was described in this case report.


Introduction
Domestic animals were widely suffering from tumors of different origins. Mammary neoplasms are among the most common neoplasm in female dogs originating from the mammary gland. A tumor is an abnormal mass of tissue resulting from autonomous, progressive, excessive proliferation of body cells not integrated into normal tissue and exhibits varying degrees of fidelity to their precursors [1][2][3]. It may be classified by their primary site of origin, grade, stage (tumor size (T), the degree of regional spread or node involvement (N), distant metastasis (M) (TNM staging), and their histological or tissue types. However, the commonly used and most useful classification of tumors is histogenetic, that is, the tumors are named according to the tissues from which they arise and of which they consist [4].
Mammary tumors are most frequent in older intact bitches and queen, but they are found in other species of animals as well. There are two published articles (the first in 1974 and modification in 1999) that describe the histologic classification systems for canine mammary tumors and dysplasia in different species of animals (Goldschmidt et al., 2011). Mammary tumors were characterized by severe cellular and nuclear pleomorphism, and highly infiltrative that represents a serious problem in veterinary medicine [3,5].
The exact cause of mammary tumors is poorly understood in any species including in dogs or cats; however, genetic and nutritional factors are considered as a possible cause. In mice, an oncornavirus is causative in certain inbred strains. In dogs, one single nucleotide polymorphism (SNP) in exon 9 of BRCA1 and one SNP in exon 24 of BRCA2 was found to be significantly associated with canine mammary tumors. The consumption of red meat and obesity are associated with an increased risk of mammary gland tumors in intact or ovariohysterectomized dogs [1,6]. Even though the exact mechanism is tumor genesis is unknown, estrogen or progesterone (or both) hormones play an important role in the hyperplasia and neoplasia of mammary tissue. They may also influence the pathogenesis of hormone-induced mammary neoplasia as well as the response to hormone therapy [7,8].
The frequency of mammary neoplasia in different species varies tremendously. The dog is by far the most frequently affected domestic species, with a prevalence ~3 times that in women; ~50% of all tumors in the bitch are mammary tumors. Mammary tumors are rare in cows, mares, goats, ewes, and sows. There are differences in both biologic behavior and histology of mammary tumors in dogs and cats. Approximately 45% of mammary tumors are malignant in dogs, whereas ~90% are malignant in cats, and dogs have a much higher number of complex and mixed tumors than do cats [9,10].
The risk of developing mammary neoplasia can be reduced by ovariectomy before the first estrus. The risk can be minimized up to 0.5% in intact bitches whereas ovariectomy after one estrus reduces the risk to 8% of that in intact bitches. Bitches neutered after maturity have generally been considered to have the same risk as intact bitches. However, questions remain regarding the impact of ovariohysterectomy at the time of tumor excision and the timing of surgery relative to survival. In one study, dogs spayed less than 2 years old before tumor excision lived 45% longer than either intact dogs or those spayed greater than 2 years old before tumor excision [11,12].
Canine mammary tumors (more than 50%) are benign mixed tumors; however, a smaller percentage of malignant mixed tumors (epithelial or mesenchymal components or both) are seen.
Histologically, canine mammary gland tumors have been classified by the World Health Organization as carcinomas (with six types and additional subtypes), sarcomas (four types), carcinosarcomas (mixed mammary tumors), or benign adenomas. This classification is based on the extent of the tumor, involvement of lymph nodes, and presence of metastatic lesions (TNM system); it includes unclassified tumors and benign dysplasias. In addition to tumor size and the status and timing of neutering, special stains (including those for the KIT receptor and AgNOR) may have prognostic value [13][14][15].
A mammary tumor is usually suspected of the detection of a mass during a physical examination and it commonly affects the two posterior mammary glands than the other three anterior glands. Grossly, tumors appear as single or multiple nodules (1-25 cm) in one or more glands. The cut surface is usually lobulated, gray-tan, and firm, often with fluid-filled cysts. Mixed mammary tumors may contain grossly recognizable bone or cartilage on the cut surface [16]. The palpation of the regional lymph nodes can help determine the extent of spread. Thoracic radiographs, preferably three views (a ventral-dorsal and two laterals), should be taken to detect pulmonary metastases. Fine-needle aspirates may differentiate between inflammatory and neoplastic lesions but may lead to erroneous conclusions and delay of surgery. The diagnosis is determined by histopathology and is important in defining treatment and prognosis [11,16,17].   Figure 1A).

Case History and Presentation
After a detailed clinical examination and thorough palpation, the tumor mass was located subcutaneously, painless, hard consistency, well-circumscribed and was attached to structures beneath it ( Figure 1B). The clinical parameters like heart rate, respiration rate, and temperature were within physiological limits.
The cut surface appeared multilobulated, papillary like projections, and white to grey in color. A biopsy sample of tumor mass was taken for histopathological examination of the lesions and the samples were preserved in 10% neutral buffered formalin.

Animal Handling, Preoperative Patient Preparation, and Anesthetic Protocol
Preoperatively, the dog was withheld 12hrs from feed and 6 hours from water before coming to the clinic based on an appointment.
The dog then was properly restrained and premedicated with chemical methods using Ana-Sed® (xylazine HCl, Heartland Vet Supply Ltd at dose rate of 1.1mg/kg, Intramuscularly). After proper sedation, the dog was positioned in lateral recumbency and the area around tumor mass was washed with water and soap thoroughly after deep sedation (Figure 2A). Then, the hair surrounding of the swelling was aseptically prepared by clipping, shaving, scrubbing, washing with water, and salvon® (Cetrimide 3% and Chlorhexidine gluconate 0.5% solution).

Laboratory Examination and Finding
The mammary gland tumors in this case report was located on the caudal thoracic pairs of mammary glands. The gross characteristics of this tumor was well-circumscribed masses, diffuse swellings well attached to the body mass, and skin-covered to ulcerate in ventral side. Besides, the mass has had necrotic material with firm and irregular shape (Figure 2A). at a thickness of 5μm using a rotatory microtome. These sections were stained with hematoxylin-eosin staining and were mounted on frosted-end glass slides using DPX mountant [19]. Finally, all the slides were microscopically examined under light microscope.
Histopathological examination of the biopsy of the tumors showed malignancy-free tissue, composed of higher nuclear to cytoplasm ratio, cellular pleomorphism, and prominent nucleoli (arrows in Figure 3) with increased numbers of mitotic figures (double nucleus and nuclear fragmentation). Finally, based on clinical and histopathogical findings, the case was diagnosed as a canine mammary tumor, and was decided to be undergone surgical excision of the mass (Unilateral mastectomy).

Post-Operative Follow-up and Result
Post-surgery, small skin bleeding was noticed but it is normal and helps to heal the wound unless continued for a long period.
The owner was also advised to aseptically wash the surgical site at the second-and third-days post-operation. Besides, modified plastic collar was applied to avoid licking on the surgical site and Penicillin (24mg/kg) and dihydrostreptomycin sulphate (30mg/ kg) (PenStrep®Norbrook UK) I.M was administered for three consecutive three days. Meloxicam, at a dose rate of 0.5mg/kg, IM) was given twice daily for three successive days for pain management.
Moreover, the owners were also advised to subjectively assess for discomfort, unpleasant discharges, pain, and inflammation at the surgical site. No signs of recurrence were present during this period.
The postoperative evaluations showed good healing progress of the surgical wound and good general condition of the patients, as well.  [21], and mixed tumors and carcinoma are diagnosed in 50-65% and 25-40% of cases of mammary tumors, respectively [9,21]. Moreover, the majority of the mammary gland tumors macroscopically showed a hard or an elastic consistency but some of them appeared fluctuant with edema or necrotic areas.

Discussion and Conclusion
Moreover, in the great majority of cases, the aspect of the tumor on the cut surface was white to grey and lobed [22]. This report was in agreement with this study.
Histologically, the mammary gland tumors showed malignancyfree tissue, composed of higher nuclear to cytoplasm ratio, cellular pleomorphism, and prominent nucleoli with increased numbers of mitotic figures. This general feature of tumors in this study agreed to the report by Goldschmidt et al. [17] who described similar histological characteristics including hypercellularity, hyperplasia, hyperchromasia, nuclear and cellular pleomorphism, high nuclear to cytoplasmic ratio and moderate to severe mitotic figures with prominent nucleoli in canine.
Unilateral mastectomy was performed that involves removal of all mammary tissue on one side of midline ( Figure 2B). This includes lumpectomy (remove all skin), mammary tissue, and fat down to the rectus fascia without removing the rectus fascia. Moreover, there was no recurrence of tumor. The reason for non-recurrence