Simultaneous Occurrence of Hemangiosarcoma and Grade II Mast Cell Tumor in a Pit Bull Terrier

Background: The incidence of cutaneous neoplasms in dogs is high and quite variable. Hemangiosarcoma (HSA) and mast cell tumor (MCT) are commonly diagnosed neoplasms in isolation; however, reports of concomitant occurrence in a single patient are rare. HSA is a malignant mesenchymal neoplasm of endothelial origin; the spleen is the most commonly affected organ. MCT is a common neoplasm that may affect any region of the body, without predilection for sex, although some breeds have shown higher incidence. This report describes a case of HSA and MCT in a Pit bull terrier.Case: A 5-year-old white male Pit bull was presented to the Small Animal Clinic of the Federal Rural University of Pernambuco with nodules in preputial region measuring 5,4 x 3,7 cm and an ulcerated nodule in the right lateral thoracic region measuring 23,0 x 19,0 x 5,5 cm. The owner reported surgical excision of two previous nodules one year before the consultation, but neither were submitted for cytopathological or post-surgical histopathological examination. Two months after the procedure, the nodules recurred. Cytopathological examinations of preputial and lateral thoracic nodules were performed, with a suggestive diagnosis for HSA and MCT, respectively. Due to the unfavorable prognosis and the weakness of the animal, euthanasia was elected. Necroscopic examination revealed an ideal body condition score (4/9), hypertrophy of right pre-scapular and axillary lymph nodes, red hepatization in the apical lobe of the right lung, with multiple, soft and pigmented nodules in the spleen, liver, pancreas and testis. Several tissue samples were collected, conditioned in 10% buffered formaldehyde solution, routinely processed for histology, and stained with hematoxylin-eosin and toluidine blue. Microscopically, the lateral thoracic nodule consisted of round cells in cordonal arrangement, with sparse basophilic and discretely granular cytoplasm, and a round, central nucleus with a single evident nucleolus. Some cells were positively marked by toluidine blue, and the neoplasm was classified as grade II MCT. The preputial and digital nodules were confirmed as well-differentiated HSA, with fusiform cells forming vascular structures containing large numbers of erythrocytes and irregular fibrovascular stroma. Metastases of HSA were observed in the lung, liver, spleen, pancreas, and testis. Invasion of mast cells was observed in lymph node.Discussion: Although the etiology of HSA has not yet been clarified,