| disease | Soft Osteosarcoma |
In 1955, Lichtenstein reported a group of cartilage tumors originating from the periosteum and named them periosteal osteosarcoma. In 1958, Jaffe introduced the concept of parosteal osteosarcoma. Generally speaking, chondrosarcoma of bone is a malignant tumor originating from cartilage tissue. Based on its location, it can be classified into central and peripheral types. The former occurs within the medullary cavity or the cortex, while the latter arises beneath the periosteum or from the periosteum itself. According to the tumor's development process, it can also be divided into primary and secondary types. The primary type occurs at an earlier age, has a higher degree of malignancy, progresses rapidly, and has a poor prognosis. The secondary type results from the malignant transformation of benign tumors such as osteochondroma and enchondroma, occurs later, progresses slowly, and has a slightly better prognosis, accounting for 4% of chondrosarcomas.
bubble_chart Pathological Changes
The main components of soft osteosarcoma are neoplastic chondrocytes, calcified cartilage, and chondroid bone. Within the primary tumor tissue, small islands of osteoid-like tissue or tumor bone may occasionally be observed, along with small amounts of myxoid tissue and fibrous tissue. In some cases, the myxoid tissue may proliferate, leading to a pathological diagnosis of myxoid fleshy tumor. Macroscopically, the affected bone shows slight expansion in shape, with thickened and roughened cortical surfaces, often accompanied by depressions. In some cases, complete local destruction of the cortical bone may occur, forming a prominent tumor mass connected to the bone tissue. Some tumors may undergo degenerative changes, resulting in pseudocyst formation or myxoid degeneration. Peripheral soft osteosarcoma may present as spherical or coarse nodular masses. The cut surface reveals numerous polyhedral small bodies, which are firm and bluish-white in color.
Under the microscope, soft osteosarcoma primarily exhibits disorganized tumor tissue composed of chondrocytes of varying sizes, along with a few myxoid cells, widely scattered within the chondroid matrix. Partial calcification or ossification of the cartilage may occur irregularly. The degree of differentiation may vary in different parts of the same tumor, necessitating careful examination and observation.bubble_chart Clinical Manifestations
Primary osteosarcoma usually occurs in individuals under the age of 30, with a higher incidence in males than females. It commonly affects the long bones of the extremities, particularly the metaphysis of the distal femur, proximal tibia, and proximal humerus. Other sites such as the ribs, ilium, scapula, or sternum may also be involved, while occurrences in short bones are rare. The main symptom is dull pain, which may progress from intermittent to persistent and can restrict the movement of adjacent joints. Sometimes, a local mass may be palpable without significant tenderness, and the surrounding skin may exhibit congestion and redness.
Secondary osteosarcoma typically occurs in adults over 30 years old, with a higher prevalence in males. It frequently arises in the pelvis, followed by the scapula, femur, and humerus. The primary manifestation is a slowly growing mass with minimal pain, and the surrounding skin does not show redness or heat. When the tumor is near a joint, it may cause joint swelling and restricted movement. If it compresses nerves, it can lead to radiating pain or numbness. Tumors located in the thoracic cavity or pelvis are often difficult to detect until they compress internal organs and produce corresponding symptoms.
(1) **Central type**: More common than the peripheral type, predominantly primary. In primary cases, the tumor originates in the medullary cavity of the metaphysis, appearing as a large unilocular or multilocular radiolucent area with irregular margins, interspersed with irregular calcifications and bone fragments. Sometimes, abundant flocculent calcifications and bone-dissipating ecchymotic masses may obscure the bone area, forming a dense shadow. The tumor's expansive growth may thin the cortical bone. Once the tumor breaches the cortex or causes a pathological fracture, it rapidly invades surrounding soft tissues, forming a soft tissue mass with scattered calcifications. Due to tumor stimulation, multilayered new bone formation often occurs beneath the periosteum, thickening the cortex or creating a "cuff" sign when the tumor breaks through the new bone. Secondary tumors exhibit increased osteolytic radiolucency, blurred margins, and clustered calcifications that may dissolve and disappear. Eventually, the tumor penetrates the cortex, developing and forming calcified shadows in soft tissues.
(2) **Peripheral type**: Less common than the central type, with secondary cases more frequent than primary ones. Malignant transformation of osteochondroma often manifests as an enlarged and thickened cartilage cap on the original osteochondroma, forming a poorly defined cartilaginous mass. The tumor and surrounding soft tissues contain numerous scattered speckled or flocculent irregular calcifications. Occasionally, coarse and elongated new bone formation may occur, with the bone portion also showing disordered trabeculae and destructive signs. In addition to rapid growth, malignant transformation of bone tumors may cause the disappearance of typical bone tumor features due to tumor destruction. A few cases may exhibit a cuff-like periosteal reaction.
The most effective method is surgical resection. After a clear diagnosis, the appropriate procedure—local en bloc resection, segmental resection, or amputation—should be considered based on the specific case. For most soft osteosarcomas, the primary goal of surgery is complete local excision. Amputation or disarticulation is reserved for recurrent cases or those with high-grade malignancy and rapid progression. The 5-year survival rates for low-grade, grade II, and grade III malignant soft osteosarcomas are 78%, 53%, and 22%, respectively.
(1) Soft bone tumor There are also scattered sand-like calcification points within the tumor, but they are smaller and fewer in number compared to soft bone tumors. The bone cortex is intact, with no bone membrane reaction.
(2) Osteosarcoma This tumor is composed of tumor-like osseous tissue and bone tissue derived from fleshy tumor connective tissue. The tumor bone contained in osteosarcoma is characteristic.
(3) Chondrofibrous fleshy tumor In terms of tissue arrangement pattern, it appears as a benign lesion with a low recurrence rate.
