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.

Hemangiosarcoma is a mesenchymal neoplasm originating in the endothelial cells of blood vessels; they can be classified as non-visceral and visceral types. Non-visceral hemangiosarcomas can affect the skin, subcutaneous tissues, and muscle tissues; visceral hemangiosarcomas can affect the spleen, liver, heart, lungs, kidneys, oral cavity, bones, bladder, uterus, tongue, and retroperitoneum. Among domestic species, dogs are most affected by cutaneous HSA. Cutaneous HSA represents approximately 14% of all HSA diagnosed in this species and less than 5% of dermal tumors, according to North American studies. However, Brazilian epidemiological data demonstrate a higher prevalence, which may represent 27 to 80% of all canine HSAs and 13.9% of all skin neoplasms diagnosed in this species. Cutaneous HSA most commonly affects middle-aged to elderly dogs (between 8 and 15 years old), with no gender predisposition for either the actinic or non-actinic forms. The higher prevalence of cutaneous HSA in some canine breeds is related to lower protection from solar radiation, as low skin pigmentation and hair coverage lead to greater sun exposure. Actinic changes, such as solar dermatosis, are frequent in these patients, confirming the influence of solar radiation on the development of this neoplasm. There are multiple clinical manifestations of hemangiosarcoma in canines. The diagnostic approach and staging classification of cutaneous HSAs are similar between the different subtypes. The definitive diagnosis is obtained through histopathological analysis of incisional or excisional biopsies. Cytology can be used as a presurgical screening test; however, it has little diagnostic utility in cases of HSA because there is a high risk of blood contamination and sample hemodilution. Surgery is generally the treatment of choice for dogs with localized non-visceral HSA without evidence of metastatic disease. Recently, electrochemotherapy (ECT) has emerged as an alternative therapy for the local ablative treatment of different neoplastic types; the use of radiotherapy for the treatment of dogs with cutaneous HSA is uncommon. There is greater consensus in the literature regarding the indications for adjuvant chemotherapy in subcutaneous and muscular HSA; doxorubicin is the most frequently used antineoplastic agent for subcutaneous and muscular subtypes and can be administered alone or in combination with other drugs. Other therapies include antiangiogenic therapy, photodynamic therapy, the association of chemotherapy with the metronomic dose, targeted therapies, and natural products. The benefits of these therapies are presented and discussed. In general, the prognosis of splenic and cardiac HSA is unfavorable. As a challenging neoplasm, studies of new protocols and treatment modalities are necessary to control this aggressive disease.

Background: The lung-digit syndrome is a rare syndrome characterized by the presence of a primary pulmonar neoplasia manifesting metastasis to the digit, occurring exclusively in felines. The diagnosis is based on the clinical signs, associated with radiographic and histopathological exams. There are no therapeutic protocols well-established, and surgical excision is considered controversial due to high recurrence and metastasis rates. The prognosis is considered poor, with low survival rates. The aim of this paper is to report a case of lung-digit syndrome attended in Rio de Janeiro.Case: A 12-year-old female cat, no defined race, was attend with the complaint of weight loss and injury in the right thoracic limb, already having histopathological diagnosis of squamous differentiation adenocarcinoma through biopsy. Physical examination showed no other clinical signs at first, including no signs of respiratory disease. Laboratory and imaging exams were performed, and the radiographic examination showed alterations in the pulmonary parenchyma showing a nodular area of increased radiographic density. Followed up by the manifestation of breathing noise at rest, as the first respiratory signs. The association of the clinical evaluation, medical history, and histopathological report from the limb lesion, lead to the suspicion diagnostic of lung-digit syndrome. The owners decide for the palliative treatment with chemotherapy, using carboplatin and prednisolone. Only the first session was performed, with the animal being euthanized due to clinical worsening 48 days after the initial manifestation of clinical signs. The diagnosis was confirmed by post mortem exams, and the pulmonary nodule were diagnosed as adenocarcinoma with squamous differentiation in concordance with the limb lesion diagnosis.Discussion: The lung-digit syndrome is still poorly studied in the veterinary medicine, with few reports published. Epidemiological data shows major incidence in elderly cats, with no racial or sexual predisposition, occurring in a 12-year-old cat in the present case. There are few theorys to explain the etiopathogenesis of the syndrome, however, none have been fully comproved. The clinical symptomatology varies from asymptomatic animals to those manifesting nonspecific systemic signs and respiratory signs. In this case the animal initially manifested only the presence of the digit injury and weight loss, with respiratory signs manifesting later. The digital lesion local signs usually include swelling, ulceration, purulent discharge, nail loss, and pain, occurring more frequently in the thoracic limbs, involving weight-bearing digits, as in the present report that occurred in the right thoracic limb, with involvement of the first and third digits. Radiographic findings may help in the diagnosis suspicion, having the confirmation by histopathological examination. The most frequent histological types involved in the syndrome are the adenocarcinoma, bronchoalveolar carcinoma, squamous cell carcinoma and adenosquamous carcinoma. The squamous-differentiated adenocarcinoma or adenosquamous carcinoma, as described in the histopathological report in the present case, is the least frequent. The treatment protocol is not well-established with no proven effective treatment. Surgical excision is not recomended as a palliative method, and the chemotherapy and radiotherapy sucess rates are still unknown. The prognosis is considered extremely unfavorable and early diagnosis represents the best attempt to control the disease.

Background: Canine transmissible venereal tumor (TVT) is one of the most common canine neoplasms in Brazil. Lesions develop mainly in the genital tissue and less frequently in other areas, in the extragenital form. Metastasis is rare, and the disease progression depends on the patient's immune status. The treatment of choice is chemotherapy with vincristine sulfate, considered an effective and safe modality. The present work describes the first case of extragenital TVT in the larynx with pulmonary metastasis at the time of diagnosis. Case: An approximately 4-month-old mixed-breed bitch was attended manifesting acute clinical respiratory signs. The patient had been rescued from the street 2 months beforehand. Physical examination revealed pale mucous membranes and crackling pulmonary auscultation. Thoracic radiography was performed in 3 projections, showing multiple nodules in the lung parenchyma, followed by cytopathological examination using fine needle puncture guided by thoracic ultrasound, confirming the diagnosis of TVT. Considering the cytological finding and the absence of primary tumor lesions in the genital, oral, cutaneous or nasal regions, endoscopy was performed in order to locate a possible primary focus. The exam revealed a small erythematous tumor with smooth and regular surface, measuring approximately 2.5 cm, located in the larynx, between the arytenoid cartilages. Chemotherapy was performed with vincristine sulfate with radiographic follow-up throughout the treatment. Full remission of the pulmonary and laryngeal nodules was achieved at the end of the protocol. The animal remained in complete remission for a period of 2 years. Discussion: TVT is more frequently observed in animals of active reproductive age, and rarely in animals under 1 year of age, as in the case described here. When considering extragenital lesions, the manifestation can be single or multiple, occurring more frequently in the cutaneous, oral and nasal forms. This case describes a laryngeal lesion with pulmonary involvement, without lesion in the genitalia or any other site. Cases of TVT in young and prepubescent animals, associated with extragenital involvement and aggressive behavior, similar to this case, have been described in literature, but never in this location. Literature suggests there is a relationship with the immune status of such patients, which do not have a well-developed immune system, facilitating disease progression. In these animals, transmission can be maternal, since in some cases the patient develops the disease without having contact with other animals except the mother. This form of transmission would facilitate the extragenital form in the oral cavity, airways and ocular region, related to licking, lactation and direct contact. Vincristine sulfate chemotherapy, considered the treatment of choice, was effectively used in this case, despite the atypical form. The TVT prognosis tends to be favorable, with the exception of the aggressive presentations with the presence of distant metastases. However, in the case described here, even though metastatic pulmonary nodules were present, complete remission was achieved, with survival exceeding 2 years. The development of TVT in the larynx is a rare form of the disease, and this report is possibly the first description of this tumor location. Thus, we highlight the importance of a complete investigation of the patient and of TVT as a differential diagnosis in this location. Keywords: dog, bitch, coitus, neoplasm, round cells, extragenital. Título: Tumor venéreo transmissível canino em laringe com metástase pulmonar Descritores: cão, cadela, coito, neoplasia, células redondas, extragenital.

Resumo. O mastocitoma está entre os tumores de pele mais comuns nos cães, possuindo grande importância na rotina clínica e cirúrgica, porém sua ocorrência em animais abaixo de um ano de idade é considerada rara, acometendo geralmente animais de meia idade a idosos. Seu diagnóstico é feito através de exames anatomopatológicos, principalmente a histopatologia, que permite a graduação e avaliação prognóstica. O tratamento pode envolver múltiplas abordagens terapêuticas, como a quimioterapia, eletroquimioterapia, inibidores dos receptores tirosinoquinase, radioterapia e criocirurgia, no entanto a modalidade mais indicada é a excisão cirúrgica, que possibilita a maior chance de cura do animal. O prognóstico para o mastocitoma pode variar de acordo com a sua graduação e fatores clínicos, além dos fatores imunoistoquímicos, que possuem grande relevância prognóstica porem ainda não são considerados rotineiros. O presente trabalho relata o caso de um canino com manifestação de um nódulo aos nove meses de idade, sendo realizada a exérese cirúrgica, com envio da amostra para avaliação histopatológica e posteriormente, imunoistoquímica. O tumor foi diagnosticado como mastocitoma e classificado como baixo grau segundo a graduação de Kiupel, e grau II segundo a graduação de Patnaik, além de manifestar um padrão c-Kit II e marcador de proliferação Ki -67 de 4, em exame de imunoistoquímica. Foi realizado protocolo de quimioterapia metronômica com o uso de clorambucil 4mg/m² associado à prednisona 1mg/kg, atingindo 60 dias livre de quaisquer sinais da doença, e recebendo a alta oncológica, permanecendo apenas em acompanhamento. A ocorrência de casos de neoplasias malignas em animais de idades precoces é preocupante e requer estudos mais aprofundados.