Mast cell tumors (MCTs) are hematopoietic neoplasms composed of mast cells. It is highly common in dogs and is extremely important in the veterinary oncology field. It represents the third most common tumor subtype, and is the most common malignant skin tumor in dogs, corresponding to 11% of skin cancer cases. The objective of this critical review was to present the report of the 2nd Consensus meeting on the Diagnosis, Prognosis, and Treatment of Canine Cutaneous and Subcutaneous Mast Cell Tumors, which was organized by the Brazilian Association of Veterinary Oncology (ABROVET) in August 2021. The most recent information on cutaneous and subcutaneous mast cell tumors in dogs is presented and discussed.

Surgery is the treatment of choice for regional control of mammary neoplasms in female dogs. Various surgical techniques may be used, as long as mammary gland anatomy, lymphatic drainage, and known prognostic factors are respected. The purpose of this study was to compare surgical stress—including duration of surgery, nociception and hematological changes—and postoperative complications in dogs undergoing regional and unilateral radical mastectomy. Eighteen dogs were selected for each technique. Postoperative pain (nociception), hematological changes, and postoperative complications were compared between the two groups. The group treated with radical mastectomy had a longer surgical duration, showed more intense physiological changes, achieved higher scores on nociception scales, and experienced more postoperative complications. Compared to regional mastectomy, radical mastectomy was associated with longer surgical duration, greater nociceptive stimulus, greater surgical stress, and higher incidence of postoperative complications in dogs. Although evaluation of long-term results was not a goal of this study, it is suggested that postoperative recovery and patient quality of life should be considered when choosing a surgical approach for treating mammary tumors in dogs.

Background: Mammary tumors are among the most frequent neoplasms in female dogs, but the strategies employed in animal treatment are limited. In human medicine, hormone manipulation is used in cancer therapy. Tamoxifen citrate is a selective inhibitor of oestrogen receptors and exerts a potent anti-oestrogen effect on the mammary gland. The aim of this study was to evaluate the adverse effects when exposing healthy female dogs to tamoxifen.Methods: Tamoxifen was administered for 120 days at a dose of 0.5 or 0.8 mg/kg/day to either intact or spayed female dogs. The effects were assessed through clinical examination, haematology, serum biochemistry, ophthalmology and bone marrow aspirate examination. Ovariohysterectomy was performed and the uterus examined by histopathology.Results: Vulva oedema and purulent vaginal discharge developed with 10 days of tamoxifen exposure in all groups. Pyometra was diagnosed after around 90 days of exposure in intact females with frequencies increasing during the following 30 days of exposure. Up to 50% of dogs within the groups developed retinitis but none of the dogs had signs of reduced visual acuity. The prevalence of retinitis in each group was similar after 120 days of exposure. Haematological, biochemical and bone marrow changes were not observed. Due to the high risk of developing pyometra after prolonged exposure to tamoxifen, only spayed animals should be given this medication.Conclusions: A dose of 0.8 mg tamoxifen/kg body weight/day is recommended when treating tamoxifen-responsive canine mammary tumors. Due to the high risk of developing pyometra, ovariohysterectomy is recommended.

Background: Melanoma is the most frequent cancer in the canine oral cavity. It shows an aggressive behavior, characterized by rapid and invasive growth and high metastatic potential. Metastasis is seen in more than 80% of dogs at time of death. Adjuvant therapy should be recommended because of potential recurrence and metastasis. Oral melanoma has a poor prognosis even when adjuvant treatments are used. There are some treatment options, but the high death rate due to the disease is still a challenge. The aim of this study was to assess the overall survival of dogs diagnosed with oral melanoma and treated with adjuvant chemotherapy and immunotherapy. Materials, Methods & Results:A retrospective analysis was carried out in 20 dogs with oral melanocytic or amelanocytic melanomas. Cases were staged according to a modified World Health Organization clinical staging system for canine oral malignant melanoma. Tumor size (T1: < 2 cm; T2: 2 - 4 cm; T3: > 4 cm), regional metastasis (N0: no metastasis; N1: metastasis) and presence of distant metastasis (M0: no metastasis; M1: metastasis) are evaluated. Then, cases were divided into 4 stages: I (T1 N0 M0), II (T2 N0 M0), III (T3 N0-1 M0, Tx N1 M0) and IV (Tx Nx M1). Diagnoses were confirmed with histopathological exam and immunohistochemistry (IHC) when necessary. In poorly differentiated neoplasms, IHC was performed at the request of the submitting veterinarian using specific markers PNL-2 and Melan-A. Animals were divided into 2 groups: dogs submitted to surgery alone were included in group 1 (G1); dogs submitted to surgery associated with adjuvant chemotherapy with four 21-day cycles of carboplatin (300 mg/m²) and immunotherapy with six 7-day cycles of interferon-α (3 x 10⁶ IU/m²) were included in group 2 (G2). Twenty dogs diagnosed with oral melanoma were evaluated: 3 were included in G1 and 17 in G2. Considering clinical staging of the dogs: 7 stage II, 12 stage III and only 1 stage IV. There was no stage I patients. In poorly differentiated neoplasias, IHC was performed at the request of the submitting veterinarian using specific markers PNL-2 and Melan-A. Patient follow-up was obtained through the evaluation of patient records and telephone interviews with owners. The overall survival time (OS) was defined by the period (in days) between the date of surgical excision and the death caused by the disease. Median overall survival time was 86 days for animals in G1 and 894 days for animals in G2 (P = 0.01). Discussion: Carboplatin was considered an appropriate cytostatic drug to treat microscopic disease in oral melanoma. INF-α was chosen for immunotherapy in this study because it promotes immune system stimulation associated with an indirect antiproliferative effect on neoplastic cells. The association of INF-α and carboplatin resulted in a significant increase in overall survival, when compared to the literature, suggesting that association of chemotherapy and immunomodulation is an important strategy in the treatment of canine oral melanoma. Controlled prospective randomized trials are necessary to confirm the benefits of chemotherapy and immunotherapy association to treat canine oral melanoma. Adjuvant therapy with chemotherapy and immunotherapy was considered effective to increase overall survival and maintained quality of life of dogs diagnosed with oral melanoma.

Background: Multilobular tumor of bone (MTB) is an unusual neoplasm with variable biologic behavior which originates primarily in bone tissues. Radiographs computed tomography (CT), and magnetic resonance imaging (MRI) are useful in diagnoses and surgical planning. Tumor removal with wide surgical margins is the treatment of choice. Immunohistochemistry has been shown as an important tool in veterinary oncology to define therapeutic and prognostic decisions. The goal of this study was to report 2 distinct cases of multilobular tumor of bone, their Cox-2 and Mib-1 immunohistochemical profile and its impact on overall survival. Case: Two bitches were presented at the Oncology Department of the Veterinary Hospital in the Veterinary School of Universidade Federal de Minas Gerais (UFMG). Both had a history of a progressive, painless, circumscribed, and firm facial mass. The 1st patient was a 8-year-old intact bitch mixed breed, weighing 50 kg, that presented a fast growing right infraorbital 3-cm mass, causing eye displacement. The 2nd patient was a 7-year-old spayed bitch Labrador retriever, weighing 28 kg, that presented a left temporal 8-cm mass. Neurologic examination of both bitches was normal. Skin over the nodules was strained, but with no ulceration. Radiographic exams of the head revealed lytic and proliferative bone reaction, with loss of cortical definition in both cases. These alterations were seen on the left zygomatic arch of the retrobulbar region, involving part of the mandible and of the nasal sinus lateral frontal bone in 1st patient, and on the right temporal process of the zygomatic bone in 2nd patient. The last one, also showed a granular solid mass with little contact with skull bones. Complete blood count, biochemistry profile, electrocardiogram, and 3-view thoracic radiographs were performed. Results were within normal ranges for the species and no signs of metastasis was seen on the radiographs. Location, size, and density of the mass, adjacent tissue compression, absence of cranial invasion, and lymph node size were rigorously evaluated with CT, allowing an individualized surgical planning to achieve complete mass removal and maintenance of the function of adjacent structures. Both animals were submitted to surgery. Both tumors were fixed on 10% neutral buffered formalin and sent to the Animal Pathology Department of UFMG for histopathological examination and margin assessment. Both tumors were diagnosed as grade I MTB. Tumor immunohistochemistry was performed to identify prognostic factors that could be used to better define therapeutic treatments and to try to clarify the discrepancy in disease progression between both tumors. The 1st patient expressed 20% of Mib-1 and was considered score 2 of Cox-2. The 2nd one expressed 5% of Mib-1 and was considered score 1 of Cox-2. Considering the diagnoses and histological characteristics of the tumors, it was decided for clinical follow-up of patients without additional therapeutic complementation. Even considering incomplete surgical margins in 2nd patient, adjuvant chemotherapy was not performed, due to low mitotic index and low histological grade. The 1st patient had an overall survival of 240 days, and death was due to recurrence and disease progression; and the 2nd did not show recurrence nor metastasis after 1200 days. Discussion: Proper and individualized surgical planning and histopathological evaluation are extremely important to guide treatment decisions. However, immunohistochemistry can be important in MTB cases, to help define which patients should be submitted to surgery alone and which patients could be benefited from adjuvant chemotherapy. Keywords: MTB, Cox-2 and Mib-1 profile, neoplasm, tumor, oncology, canine, dog, bone tissues.