BONE TUMORS: Tumors of the musculoskeletal system are those growth that arise from tissues of mesenchymal and neuroectodermal origins. Malignant tumors of the musculoskeletal system are called as Sarcomas. There is no corresponding generic term for Benign tumors of mesenchymal and neuroectodermal origins. Malignant tumors are separated from Benign tumors by their ability to spread to a distant site and produce another tumor. Giant cell tumor of bone is a typical example of Benign bone tumor. Musculoskeletal tumors locally extend in the direction of least anatomic resistance. They cross barriers to enter an adjacent compartment after they have extended for some distance in their compartment of origin. Benign musculoskeletal lesions tend to extend to the surrounding normal structures. They have a reasonably intact capsule of compressed tissue and seem to destroy bone by stimulating osteoclast. Malignant tumors however infiltrate the surrounding normal tissue, invade the pseudocapsule and absorb enzymes particularly collagenases that directly reabsorb bone and collagen. Our this paper will be more concerned with the application of Allograft in Malignant tumors.

Imaging has four possible objectives 1) detection of pathology 2) diagnosis 3) staging and 4) evaluation of treatment plan¹⁴². Detection of bone tumors is not usually a challenge because most are readily apparent on routine radiography. Occasionally small lesions such as osteoid osteoma may be difficult to locate. Certain large lesions such as Ewing's Sarcoma and lymphoma may also be difficult to recognize on routine radiographs when infiltrate growth results in subtle bone destruction. Radioisotope bone scan and magnetic resonance imaging (MRI) almost detect such lesions if properly directed. Soft tissue tumors on the other hand are often difficult to detect with radiographs, especially when deeply situated in the trunks, thigh or pelvis. Special imaging process such as Computerized tomography ( CT ), MRI and radionuclide scan can usually reveal these lesions.

The staging of malignant tumors is important to prognosis and in organization of treatment, assignment of treatment, priorities and investigative studies. The first staging system for malignant tumors was that developed for cervical carcinoma by the American Joint Committee on Cancer (AJCC). An understanding of the approaches used for staging of musculoskeletal neoplasm's requires knowledge of their biological behavior and natural history. During their early growth sarcomas of the Musculoskeletal system enlarge in a centrifugal manner. A pseudocapsule of fibrous connective tissue is formed as a host reaction by compression and layering of normal tissue cells, inflammatory cells and newly formed blood vessels at the expanding border of the growing sarcoma. The reactive zone at the periphery of the pseudocapsule attempts to contain the microscopic extensions of the tumor. However satellite colonies of malignant cells may be found at some distance from the tumor. As their growth continues sarcomas of the musculoskeletal system are contained in compartments bounded by fascia, cortical bone, synovium , periosteum and cartilage. Many Sarcomas remain intracompartmental, that is they are confined within a specific anatomic compartment except in very advanced stages or if they are disrupted by a surgical procedure. Major neurovascular structures are usually displaced rather than invaded. The initial staging system for bone sarcoma was described by Enneking. It is the only system for the staging of benign musculoskeletal tumors in use and has been endorsed by the Musculoskeletal Tumor Society⁴⁹. (table 1).

Table 1. Enneking system for the staging of soft tissue sarcoma and sarcoma of bone

The biopsy of a soft tissue mass or of a radiographic apparent bone lesion is essential to embark on a treatment plan. Biopsy frequently demands relatively few technical skills. Hence, decisions related to the performance of biopsy require considerable thought and experience. Without appropriate planning or execution biopsies frequently lead to adverse effects on patient prognoses and treatment options. Poorly performed biopsies, poorly placed incisions and biopsy complications can considerably compromise the subsequent local management of bone and soft tissue tumors¹¹. The biopsy should be undertaken by the surgeon who plans to carry out the definitive treatment of the patient ⁹⁷. If bone tumor is suspected, it may be classified in one of the three main diagnostic categories viz.: 1) BENIGN BONE TUMOR - 2) MALIGNANT BONE TUMOR or 3) METASTATIC BONE TUMOR. Each of these includes specific subcategories which may often be diagnosed by careful clinical and radiographic interpretations¹⁴⁴.

Radiation therapy includes major vessels, nerves, connective tissues and hollow viscera with relatively low risk of producing complications, thus improving cosmetic and functional outcome. Modern clinical radiation therapy is delivered using linear accelerators. Pelvic tumors are the most often treated with equipment capable of delivering x-ray beam energies in the range of 10 to 25 MV¹⁴⁴. These beams offer the relative advantage of increased dose at a given depth in tissue with lower surface damage. This characteristic allows for less irradiation of nontarget tissues. In addition to conventional external beam irradiation, other specialized modalities are available for the treatment of bone and soft tissue malignancies. These include the use of Brachytherapy or the implant technique. In this technique temporary dwelling hollow catheters are placed at the time of surgery and remotely loaded with radioactive sources at a later time. However one can also use a CT guided stereotactic system for percutaneous catheter placement. Both the techniques allow high dose of radiation to be delivered to relatively small volumes of tissue.

Chemotherapy plays an important role in the treatment of high grade sarcomas in general. Osteosarcoma has provided with the best evidence of cure rate by the employment of chemotherapy¹⁰⁹. Chemotherapy plays a critical role in the treatment of tumors associated with a high incidence of micro-metastatic spread at the time of diagnosis. In mid 1980's Pediatric Oncology group (POG) performed a randomized trial for patients with localized Osteosarcoma in which patients received an amputation or limb salvage procedure and were then randomized to receive no chemotherapy or an aggressive multiagent chemotherapy regime. It was found that chemotherapy cured about 65 % of the patients⁹⁴.

The diagnostic of cancer is always shattering. It does not immediately hits, but runs down a chain of reaction in the patients mind, who like a witness to a crime absorbs the information with some denial and distortion playing in his head. He looks to the physician to take him out of this crisis with the best of treatment. It does wonders to a patient, if the physician at this points comes up with a treatment plan and mediates the points of conflict and uncertainty. Most patients value honest and compassionate information given with allowances for hope even if the news is bad. They appreciate simple respect for personal dignity and vulnerability. The physician's chamber or hospital bed is the best place to deliver the news rather than the telephone or recovery room. It is also better to divulge the information with a close family friend or a person in the family and make him understand the situation in details. As there is no Emotionmeter to measure the emotions or pains which vary from individual to individual, patients cope in their own style usually with initial distress, anxiety, anger and sadness. The strengths and weakness of their personality reflects very much at this juncture. It is very important to make the patients understand that the people with Osteosarcoma and Ewing's sarcoma do survive and that their fertility, income or employment do not differ with others . In a study carried out between 1945 to 1974 showed that most cancer patients did well and adapted to amputation or limb salvage. Rarely did they attribute martial status or lack of education to the experience of cancer¹⁴⁵.