Hemipelvectomia total em um gato com osteossarcoma osteoblástico

Background: Osteosarcoma (OSA) is a malignant neoplasm of mesenchymal tissue that exhibits various histological features and a differentiated biological clinical behavior. The combination of clinical, radiological, and histopathological features is important for diagnosis. Surgical treatment of neoplasms with pelvic involvement is a challenge. Primary bone tumors are rare in cats and are mostly reported in older animals. The objective of this paper was to report the case of a feline subjected to total hemipelvectomy as primary treatment of pelvic OSA; the surgical technique and histological analysis of the tumor are described. No signs of recurrence were seen during seven months of follow-up.Case: A 4-year-old female mixed breed cat weighing 3 kg was presented with a one year history of increased volume on the hip joint region. Palpation of the increased volume on the hip showed a firm, adhered, and painful mass. Radiographic examination of the pelvis in the dorso ventral projection exhibited a severe osteoblastic bone reaction on the proximal femur, as well as marked periosteal reaction of the hip joint with involvement of the acetabulum. A ventral approach total hemipelvectomy technique was adopted for excision of the tumor. The animal was placed on a lateral position and a circumferential skin incision was performed on the ipsilateral limb of the affected hemipelvis, on the medial portion of the femur, and was extended cranially up to the thoracolumbar region. The pubic symphysis was exposed with a periosteal elevator and a pubic symphysiotomy was performed on the midline using a Liston bone cutter; next, the sacroiliac junction was resected. No drain was used after surgery, only compressive bandages. The patient was hospitalized for post-operative monitoring which included opioids for pain management and a non-steroidal anti-inflammatory drug and a cephalosporin class antibiotic. The wound was cleaned with saline, rifamycin spray (Rifocina Spray®) was applied, and dressing was changed every 12 h. The excised bone was submitted for pathological analysis. Gross examination revealed a 4.2 cm hardened increase in volume on the area of the femoral head and acetabulum, with irregular surface; cut surface was hard and white with black and red spots. Histology revealed osteoblastic OSA with intense and solid fusiform and stellate cells distributed in a solid pattern with no capsular border, with marked infiltration of the bone tissue, marked osteolysis, modera