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.

Electrochemotherapy is a combination of high electric field and anticancer drugs. The treatment basis is electroporation or electropermeabilization of the cell membrane. Electroporation is a threshold phenomenon and, for efficient treatment, an adequate local distribution of electric field within the treated tissue is important. When this local electric field is not enough, there is a regrown tumor cell; however, if it is stronger than necessary, permanent damage to the tissue occurs. In the treatment of dogs, electrochemotherapy is not yet an established treatment for mast cell tumor in veterinary medicine, although there are studies showing evidence of its effectiveness. In this study, we examined electrochemotherapy of dog mast cell tumor with numerical simulation of local electric field distribution. The experimental result was used to validate the numerical models. The effect of tumor position and tissue thickness (tumor in different parts of dog body) was investigated using plate electrodes. Our results demonstrated that the electrochemotherapy is efficient and flexible, and even when the tumor extends into the subcutis, the treatment with plate electrode eliminated the tumor cells. This result suggests that electrochemotherapy is a suitable method to treat mast cell tumors in dog.

Gap junctions are communicating junctions which are important for tissue homeostasis, and their disruption is involved in carcinogenic processes. This study aimed to verify the influence of deletion of one allele of the Connexin 43 gene on cancer incidence in different organs. The 7, 12-dimethylbenzanthracene (DMBA) carcinogenic model, using hebdomadary doses by gavage of 9 mg per animal, was used to induce tumors in Connexin 43 heterozygous or wild-type mice. The experiment began in the eighth week of the mice life, and all of them were euthanized when reaching inadequate physical condition, or at the end of 53 weeks. No statistical differences occurred for weight gain and cancer survival time (P = 0.9853) between heterozygous and wild-type mice. Cx43+/− mice presented significantly higher susceptibility to lung cancer (P = 0.0200) which was not evidenced for benign neoplasms (P = 0.3449). In addition, incidence of ovarian neoplasms was 2.5-fold higher in Cx43+/− mice, although not statistically significant. Other organs showed a very similar cancer occurrence between Cx43 groups. The experiment strengthens the evidence of the relationship between Connexin 43 deficiency and carcinogenesis.

Polycyclic aromatic hydrocarbons are known carcinogens used in rodent experimental models. In this study, the carcinogen DMBA (7,12-dimethylbenzanthracene) was administered by gavage, diluted in corn oil, to female BALB / c mice at hebdomadary doses of 1 mg per animal for 1, 3, 6 or 9 weeks. Animals were weighed and monitored weekly until death. Remaining animals were euthanized at the age of 53 weeks. At necropsy, representative fragments of neoplasms were collected and routinely processed for histopathological analysis. Of all mice that received DMBA, 68.57% developed some type of tumor. Of the 70 mice treated with various doses of DMBA, 22 (31.43%) developed mammary tumors. The adenoacanthoma was the most commonly (18.75%) diagnosed histological type of breast cancer. Lung (15.71%), lymphoid tissue (11.43%), stomach (7.14%) and skin (2.86%) were also primary sites of tumor development. One third (33.33%) of the mice receiving 1 mg of DMBA developed lung cancer. Therefore, the administration of DMBA was shown to be an efficient model of carcinogenesis in mice, especially for the study of breast cancer, when using the highest dose, and lung, when using the lowest dose. Carcinogenesis models have been used for several purposes in cancer research. These results represent new facts for a classic carcinogenesis model. Keywords:Carcinogenesis. DMBA. Mice. Lung neoplasms. Breast neoplasms. ResumoHidrocarbonetos policíclicos e aromáticos são carcinógenos usados em modelos experimentais em roedores. Neste estudo, o carcinógeno DMBA (7,12-dimetilbenzantraceno) foi administrado por gavagem, diluído em óleo de milho, para camundongos BALB/c em doses hebdomadárias de 1 mg por animal por 1, 3, 6 ou 9 semanas. Os animais foram pesados e monitorados semanalmente até a morte. Os animais remanescentes foram eutanasiados com a idade de 53 semanas. Na necroscopia, fragmentos representativos das neoplasias foram colhidos e rotineiramente processados para exame histopatológico. De todos os animais que receberam DMBA, 68,57% desenvolveram algum tipo de tumor. Entre os 70 camundongos tratados com diferentes doses de DMBA, 22 (31,43%) desenvolveram neoplasias mamárias. O adenoacantoma foi o tumor mamário mais comumente diagnosticado (18,75%). Pulmões (15,71%), tecido linfoide (11,43%), estômago (7,14%) e pele (2,86%) foram também locais primários de desenvolvimento de neoplasias. Um terço (33,33%) dos camundongos que receberam 1 mg de DMBA desenvolveram neoplasias pulmonares. Portanto, a administração de DMBA foi considerada um modelo eficiente de carcinogênese em camundongos, especialmente para o estudo de neoplasias mamárias, quando a maior dose é utilizada, e de neoplasias pulmonares, quando utilizada a menor dose. Os modelos de carcinogênese química têm sido usados para diversos estudos na pesquisa em câncer, os resultados aqui apresentados mostram novos fatos para um modelo clássico de carcinogênese.

Electrochemotherapy (ECT) is a technique that combines chemotherapy with local application of specific electric pulses with the aim of increasing the permeability of the plasma membrane in a reversible way, improving the influx of chemotherapeutic drugs into the cytoplasm and potentiating their cytotoxic effects. This technique has broadened the range of possible treatments for oncological patients, either on its own or as adjuvant to surgical procedures. It is especially useful in tumors located in regions with only a small surgical safety margin, such as the limb extremities, skull, oral cavity, neck and perianal region, among others. ECT makes it feasible to perform procedures more conservatively, or even to perform otherwise infeasible procedures, by expanding the margins without removing healthy tissues. The objective of this paper is to provide a brief bibliographic review of the principles, applications and future possibilities of electrochemotherapy, helping to disseminate pertinent information about this relatively new technique for the treatment of cancer.