The first factor to be taken into consideration for the purpose of a correct and rapid diagnosis of osteosarcoma is that of close collaboration between the specialists involved, in particular the clinician, often the orthopedist, the radiologist, and the pathologist. In the clinical setting, elements such as the age of onset of the tumor, its location, and symptoms must be taken into consideration.
Decisive for the purpose of diagnosis are often the radiological and radiographic aspects in relation to which it must be said that osteosarcoma can show a variable degree of ossification. The higher the level of ossification, the easier the radiographic diagnosis through the detection of radiopacity. The earliest radiological aspects are represented by the presence of an irregular bone neoformation with radiolucent and / or radiopaque areas that over time affects the cortex. This involvement is evident with its erosion and overcoming with consequent involvement of the surrounding soft tissues.
Frequently there is a periosteal reaction with the production of bone trabeculae, perpendicular to the bone surface, which give a radiological appearance to ‘sun rays’. During the production of these trabeculae, the periosteum detaches towards the outside, delimiting a triangular space which constitutes the radiological sign known as ‘Codman’s triangle’.
It should be emphasized that all these characteristics, often diagnostic, can be highlighted with a classic radiograph in several projections.
Other useful imaging techniques are computed tomography (CT) and nuclear magnetic resonance (NMR) with and without contrast. The first is useful in highlighting the intramedullary extension of the sarcoma, in revealing the presence of metastases and finally in evaluating the neurovascular compromise of the joints and cortical bone. The second, on the other hand, allows us to specify the size of the tumor as well as its intramedullary extension and the involvement of soft tissues, especially in the poorly osteogenic forms.
These modern imaging techniques represent a useful guide to perform selective surgical resections and, when possible, not excessively demolitive.
Arteriography may still be of some use, in selected rare cases, while data is being acquired for a possible diagnostic validation of PET. The diagnosis of overt osteosarcoma does not usually present major difficulties both from a clinical, radiological and histological point of view, although the determination of the histotype on the biopsy material is not always easy. The essential histological aspect is the presence of bone matrix directly in contact with neoplastic cells with malignant characteristics; in the absence of frank matrix deposition, diagnosis can be difficult.