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, moderate proliferation of osteoclasts, and moderate anisocytosis and anisokaryosis.Discussion: Bone tumors in cats are rare and develop spontaneously. They exhibit aggressive behavior and promote local bone destruction. Firm consistency and local swelling usually occur in more advanced cases when there is a delay between the onset of clinical signs and the veterinary consultation. Radiological findings such as bone destruction and bone formation are commonly seen in this type of tumor. Hemipelvectomy is considered an aggressive surgical technique, but necessary in many cases, especially when tumors are located in the pelvis and nearby tissues. In the case presented here, this surgery was the most viable and advised therapeutic option because of tumor location. No incidents (i.e. hemorrhage) occurred during the perioperative period. After surgery, the patient continued to perform all custom functions. The hind limb, which was affected in this case, is commonly reported to be affected in the literature; however, it is unusual to have involvement of both bones (pelvis and femur) since vascularization of these bones are independent. Diagnosis was confirmed by histopathology in which a characteristic malignant mesenchymal tumor of primitive bone cells was present, with production of osteoid of variable shapes and quantity with the presence of osteoclastic giant cells