We report a case of a primary mesenteric tumor that was discovered in a 71-year-old man. Abdominal US accurately visualized the internal structure of the tumor but failed to determine the site of origin. Computed tomography suggested the mesenteric origin of the tumor before resection. The mass was removed and histopathological examination (including immunohistochemical and ultrastructural studies) was consistent with a primary gastrointestinal stromal tumor (GIST) of the mesentery, a very rare neoplasm scarcely reported in the radiology literature. Clinical, radiological, and pathological findings of this case are presented and the topic of primary mesenteric tumors with phenotypical features of GIST is reviewed.

Cardiac tumors are uncommon in dogs. Their etiology is unknown, and it is believed that genetic factors may have an influence on the appearance of this type of neoplasia. At the initial stage, they do not cause relevant clinical signs, but as the primary tumor progresses, cardiac function is affected. These tumors may be confused with congestive heart failure. Hemangiosarcoma is one of the most frequent cardiac neoplasms and may have several locations, but it usually affects the right atrium. Cardiac neoplasms do not usually metastasize, but have poor prognosis for patients. Therapeutic alternatives, when possible, include surgery and chemotherapy. The objective of the present study was to report a case of primary cardiac hemangiosarcoma in an eight-year-old Dachshund bitch, presenting the clinical alterations found, the complementary exams performed and the final diagnostic confirmation through necropsy and histopathological examination.