Carcinossarcoma em Glândula Tireoide com Potencial Metastático: Aspectos Clínicos e Patológicos em um Canino

Resumo

Background: Thyroid neoplasms are the most common endocrine neoplasms and are classified according to their histological characteristics. Canine thyroid carcinosarcomas correspond to rare and uncommon neoplasms, they are malignant mixed tumors, constituted by follicular and mesenchymal epithelial cells. This neoplastic type is extremely aggressive, locally invasive and has a high ability to metastasize, especially to the lungs. The present work aimed to report a peculiar case of carcinosarcoma in the thyroid gland with metastasis in a canine.Case: A 9-year-old mixed breed female dog was treated at the veterinary hospital of the Universidade Federal Rural do Semiárido (UFERSA) with dyspnea, hyporexia and weight loss. On physical examination, there was an increase in volume in the ventral cervical region, with a characteristic of hard consistency, a decrease in the body condition score, noise and snoring on respiratory auscultation. Complementary exams were performed, including imaging exams, cervical ultrasonography and thorax radiography. Ultrasonography showed the formation of irregular contours superimposed on the right and left thyroid lobes, occupying a large part of the ventral area, while the radiography suggested the presence of diffuse neoplasm in the lung. Due to the evolution of the animal's clinical condition and poor prognosis, the owner opted for euthanasia of the animal, which was then sent for necroscopic examination. During necropsy, bilateral neoformation was observed adjacent to the tracheal rings and in both lungs completely affected by nodules and tumors, with hard consistency and rough surface. Fragments of the neoformation adjacent to the trachea, as well as the lung tissue were collected, fixed in formaldehyde and sent for histopathological analysis. Microscopic evaluation of tissue adjacent to the trachea revealed the presence of a carcinosarcoma in the thyroid gland; microscopic evaluation of lung tissue was similar to thyroid findings. Thus, a primary carcinosarcoma in the thyroid gland with lung metastasis was defined. Thyroid carcinosarcoma can be a challenging diagnosis in canine medicine and often leads to a poor prognosis.Discussion: In dogs, the etiology of thyroid neoplasia is still unknown, but the hypothyroidism and ionizing radiation are reported as risk factors. Neoplasms of the thyroid gland represent between 10 and 15% of head and neck formations in dogs, being an important differential diagnosis in the medical clinic routine. According to the literature, carcinosarcomas are rare and extremely invasive neoformations, whose treatment depends on the size and invasiveness. The patient's prognosis in most cases is reserved to unfavorable. Early diagnosis is important in managing the case, for rapid intervention. In the reported case, the clinical signs were observed late and the complementary exams were essential for the patient's diagnosis, suggesting the presence of lung metastasis. Later in the necropsy, neoformation was observed adhered to some structures, compromising part of the trachea and consequently the patient's breathing. Samples were collected for histopathological analysis and the result confirmed an aggressive and invasive case of carcinosarcoma in the thyroid gland.