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Osteosarcoma is an immature neoplasm that forms osteoid and neoplastic bone produced by malignant osteoblasts, with a strongly sarcomatous stroma. Histologically, it may appear as osteoblastic, chondroblastic, fibroblastic or teleangectatic, depending on the similarity of its cells. After myeloma, it is the most common primitive bone neoplasm.

Osteosarcoma

It affects young people in the first and second decade, affecting the metaphyseal region of long bones, close to the growth plate. Clinically, it presents  pain  in the affected region,  heat  due to hyperemia,  tumor  due to increased local volume plus some  functional limitation .

Radiographically, it presents a lesion in the metaphyseal region characterized by areas of new bone formation interspersed with areas of bone rarefaction, with imprecise limits, with cortical erosion and a thin lamellar periosteal reaction, forming Codman’s triangle. The presence of Codman’s triangle denotes the existence of an extra-cortical tumor.

Para o diagnóstico dos tumores ósseos é preciso fazer a correlação entre a clinica, a radiologia e a anatomia patológica.
To diagnose bone tumors, it is necessary to make a correlation between the clinic, radiology and pathological anatomy.

Codman’s triangle (figure 2) is a radiographic sign that occurs in other conditions such as osteomyelitis, eosinophilic granuloma, Ewing’s sarcoma and other tumors. It can appear whenever a lesion occurs inside a bone and grows outside of it. When the lesion  (or pus in osteomyelitis)  surpasses the cortical bone, it causes detachment of the periosteum that was attached to the cortical bone. The lesion therefore grows and this detachment stimulates the periosteum to produce bone. In this way, a layer of mineralization occurs as if a neocortical was formed. This process can occur successively, forming true layers (lamellae) (figures 3a and 3b). These layers can be thin  (thin lamellar periosteal reaction – characterizing the growth speed of the lesion)  or thick   (thick lamellar periosteal reaction – characterizing slow growth) . As the lesion progresses, this attempted “barrier” ruptures and a triangle appears radiographically delimited  externally by the periosteum  (which was successively detached and removed from the bone cortex),  internally by the  bone cortex and at the  base by the  expanding tumor.

         The imaging study of the lesion can be more detailed using tomography (figure 3c), which allows the evaluation of erosion of the bone cortex and extra-cortical involvement. Magnetic resonance imaging is important to define the extent of the tumor, both in the medullary and extracortical areas (figures 4d, 4e and 4f). This exam also allows you to evaluate the relationship between the tumor and the soft parts (muscles, vessels and nerves) and is essential for surgical planning.

Figura 2: Triangulo de Codman (presente em osteossarcoma, osteomielite, sarcoma de Ewing e granuloma eosinófilo).
Figure 2: Codman's triangle (present in osteosarcoma, osteomyelitis, Ewing's sarcoma and eosinophilic granuloma).
Figura 3: a) osteossarcoma com triângulo de Codman; b) reação periosteal lamelar fina; c) tumor produtor de osso.
Figure 3: a) osteosarcoma with Codman’s triangle; b) thin lamellar periosteal reaction; c) bone-producing tumor.
Figura 4: d) lesão heterogênea, limites imprecisos; e) epífise sem lesão; f) lesão extra cortical.
Figure 4: d) heterogeneous lesion, imprecise limits; e) epiphysis without injury; f) extra-cortical lesion.
The current treatment of osteosarcoma consists of preoperative polychemotherapy, for approximately 3 to 4 cycles, followed by complete resection of the tumor and complemented with postoperative chemotherapy. It is currently possible to resect the tumor (figures 5, 6 and 7) and reconstruct the affected segment with prostheses or biological solutions (figure 6) (autologous or homologous bone graft). Ablative surgeries (amputations) are reserved for cases of advanced tumor, of large volume, compromising the skin and/or vascular-nervous bundle or in those cases that did not obtain a good response to pre-operative chemotherapy and whose conservative resection, with preservation of the limb , implies a risk of local recurrence of the lesion.
Figura 5: a) osteossarcoma com fratura consolidada, pós quimioterapia.
Figure 5: a) osteosarcoma with healed fracture, post chemotherapy.
Figura 6: b) ressecção transepifisária; c) corte axial da placa de crescimento, removida com a lesão.
Figure 6: b) transepiphyseal resection; c) axial cut of the growth plate, removed with the lesion.
Figura 7: d) reconstrução com autotransplante de fíbula vascularizada, preservando sua placa de crescimento, encaixada em enxerto homólogo e estabilizada com placa angulada e dispositivo de fixação interna extensível.
Figure 7: d) reconstruction with autotransplantation of a vascularized fibula, preserving its growth plate, embedded in a homologous graft and stabilized with an angled plate and an extensible internal fixation device.

Author: Prof. Dr. Pedro Péricles Ribeiro Baptista

 Orthopedic Oncosurgery at the Dr. Arnaldo Vieira de Carvalho Cancer Institute

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