In general, any patient with a bone mass with indeterminate imaging results should be referred to an orthopedic oncologist.
When imaging findings are highly suggestive of bone sarcoma, efforts should be made to delineate how far the tumor extends and whether systemic disease is present. Bone sarcomas can metastasize to other bones, but their most common site for metastasis is the lung.
MRI of the lesion without gadolinium is indicated, and the entire bone is imaged to determine the extent of the external mass outside the bone and to look for medullary extension and skip lesions (eg, smaller foci of sarcoma occurring in the same bone or on the opposing side of a joint). The precision offered by MRI has dramatically increased surgeons’ ability to achieve negative margins during resection.
Radiography or computed tomography of the chest is required to accurately assess the lungs for metastasis. A nuclear medicine technetium scan can be obtained to look for other similar bone lesions (metachronous lesions) or metastatic bony disease.
Laboratory tests are not helpful in the staging of bone sarcomas.
Biopsy is the gold standard for diagnosis of bone sarcoma ( Figure 1 ). The primary biopsy methods used are needle or open biopsy techniques, and Tru-cut needles or core bone biopsy needles are increasingly used. If the core needle biopsy is diagnostically inconclusive, an open biopsy can promptly be performed. Biopsies yielding specimens that are too small can result in inconclusive pathology reports. Regardless of the biopsy technique, hemostasis is of paramount importance, and patients are generally advised to not use the affected limb for at least several days after the procedure to reduce the risk of a cancer cell–laden hematoma.
If a needle biopsy is performed, 2 to 10 minutes of gentle pressure is applied to the site. In an open biopsy, electrocauterization is used extensively. Aggressive hemostasis is achieved, and if a drain is placed it should be in proximity to the incision site itself so that the drain site will be resected with the specimen at the time of definitive resection. Open biopsies are performed in the operating room with regional or general anesthesia. Incisions are made longitudinally and never transversely.
Ideally, the biopsy should be performed or supervised by a physician experienced with limb salvage for bone sarcomas. Otherwise there is risk for an inappropriate biopsy tract or approach, misinterpretation of the radiographic studies, misinterpretation of the pathology, or biopsy complications. These errors may lead to undertreatment or even unnecessary amputation. 8,9
For some bone sarcomas, such as osteosarcoma and Ewing sarcoma, there is a preference to treat the potential micrometastatic disease at the beginning of the course, prior to surgical treatment. This may result in reduction of the soft-tissue mass about the bone tumor and/or maturing of the mass, allowing for easier resection.
Importance of margins
The goal of resection is to achieve a margin or normal cuff of tissue around the pseudocapsule of the tumor. In general, the larger the margin, the less the chance of recurrence. 10–12 Ideally, the tumor and pseudocapsule should not be violated or exposed and a margin of at least 1 cm should be obtained. It has been postulated that margins of less than 1 cm may be associated with a very low rate of recurrence, although no well-controlled study has proven this and such a study would be difficult to perform given the rarity and heterogeneity of bone sarcomas and the variability in their assessment and surgical treatment.