Thoracic and Abdominal Wall Reconstruction with Polypropylene Mesh after High Grade Infiltrative Fibrosarcoma Resection in a Dog

Background: Soft tissue sarcomas are a group of invasive malignant tumors formed by neoplastic mesenchymal cells. In most cases, the treatment require surgical resection. When sarcoma characteristics disqualify conventional tumor excision, polypropylene mesh can be used for abdominal or chest wall reconstruction. This paper aims to describe the clinical, computed tomography features, histopathlogical and immunohistochemical aspects of a chest wall fibrosarcoma, as well as to describe the tumor excision technique combined with resection of multiple ribs, diaphragm advancement and reconstruction of thoracic and abdominal wall with a synthetic polypropylene mesh. Case: An 11-year-old male Boxer was presented with a progressive growth tumor in the left paralumbar area. The invasive tumor measuring 15 cm in diameter, was firm epidermodermal coverage and was adherent to the subcutaneous tissue, having a smooth and non-ulcerative skin surface. Ultrasound of the mass consisted of a heterogeneous structure comprising paralumbar region, invading abdomen and left thoracic wall. Thoracic radiography showed no signs of nodular interstitial pulmonary pattern compatible with metastasis. The dog was submitted to a CT examination of thoracolumbar region, which demonstrated the presence of the circumscribed mass, measuring approximately 17 cm in diameter in the left paralumbar region with involvement of both paraspinal and transversus abdominis muscles in the region of T13 to L4 with a periosteal reaction of the left 13th rib. Cytopathology demonstrated fusiform cells with evident nucleoli, moderate anisocytosis, anisocariose, pleomorphism and mitotic activity. Histopathological analysis revealed infiltrative neoplastic proliferation of elongated oval tumor cells with large nucleus and abundant eosinophilic cytoplasm, confirming undifferentiated sarcoma. Further, the sample was sent for immunohistochemical analysis, which was suggestive of high-grade fibrosarcoma. The patient was referred for paralumbar neoplasia resection and plastic-reconstructive surgery. While in lateral recumbency, the animal was submitted to a circular incision around the tumor. During tumor dissection, it was noted the involvement of 11th, 12th and 13th ribs, lateral abdominal musculature, as well as the pleura, peritoneum and adjacent soft tissues, so, these structures had to be removed. After tumor removal, a 20 cm diameter thoracic and abdominal defect had to be corrected by the advancement and reintegration of diaphragmatic crus in the caudal border of the 10th rib. Closure of the abdominal wall was performed by surgical implantation of a double layer polypropylene mesh, which was fixed by sutures in the adjacent musculature. Cutaneous closure was possible by performing four tension relief incisions parallel the incision line. During postoperative period, the animal developed hypotension and severe blood loss and anemia. Six h after the surgery, the animal presented cardiopulmonary arrest unresponsive to resuscitation protocol. Discussion: Fibrosarcoma has biological characteristics of high malignancy, low metastasis rates and high invasiveness. The objective of fibrosarcoma treatment is the complete surgical excision of the tumor. En bloc excision is the main chest wall tumor treatment and includes resection of ribs, muscles, pleura and adjacent tissue to obtain clean surgical margins. In this case, primary closure of chest and abdominal wall was not possible due to extension of defect after tumor removal. The use of polypropylene mesh proved to be fundamental to lateral thoracoabdominal muscle layer closure. According to laboratory tests and the presence of hemorrhage and anemia during postoperative period, the authors believe that the patient developed disseminated intravascular coagulation, which significantly contributed to patient's death.