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Message: <blockquote data-quote="amila_90210" data-source="post: 4088810" data-attributes="member: 111009">Imaging Studies  Radiography Initial evaluation should begin with plain radiography. In  every patient with a suspected tumor, orthogonal anteroposterior (AP) and  lateral views of the affected area should be taken. This includes soft-tissue  masses as well. In many cases, radiographic examination is diagnostic, and no  further imaging studies are indicated. However, in the case of a more aggressive  process, the diagnosis may be determined on the plain radiographs but further  evaluation with advanced studies is usually indicated to determine the extent of  local soft-tissue involvement as well as to assess the extent of disseminated  disease (staging). The initial radiographic images must be scrutinized. For  bone lesions, the location within the bone (eg, epiphyseal, metaphyseal, or  diaphyseal) facilitates the diagnosis. Epiphyseal tumors are usually benign. The  more malignant primary sarcomas, such as osteosarcoma, are typically seen in a  metaphyseal location; however, round cell tumors, such as Ewing sarcoma,  multiple myeloma, and lymphomas, are usually medullary diaphyseal lesions. A  tumor arising from the surface of a long bone may be a benign lesion, such as an  osteochondroma, or it may be a low-grade sarcoma, such as a parosteal  osteosarcoma. Terms such as geographic, well circumscribed,  permeative, and are used to describe the appearance of radiographic  abnormalities. Geographic or well circumscribed implies that the lesion has a  distinct boundary and is sharply marginated, suggesting a benign tumor (Figure  6–1). A poorly defined, infiltrative process is described as permeative or moth  eaten and reflects a more aggressive processsuch as a malignancy (Figure 6–2),  although aggressive but benign processes can have this radiographic quality as  well (Figure 6–3). An exception to this rule is multiple myeloma, which  frequently demonstrates a punched-out, well-demarcated appearance but in  multiple locations.         Figure 6–1.<img src="http://www.elakiri.com/forum/Print%20Chapter%206_%20Musculoskeletal%20Oncology_files/loadBinaryCA08I3OX.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />   Radiograph of an enchondroma of the second metacarpal. Notice  its geographic  appearance.<img src="http://www.elakiri.com/forum/Print%20Chapter%206_%20Musculoskeletal%20Oncology_files/loadBinaryCAG17ARK.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />   Radiograph of a proximal fibular osteosarcoma demonstrating the  destructive, permeative nature of malignant bone  tumors.<img src="http://www.elakiri.com/forum/Print%20Chapter%206_%20Musculoskeletal%20Oncology_files/loadBinaryCA0H583A.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />   Radiograph of a giant cell tumor of the thumb. This is a typical  moth-eaten appearance. With a careful history, physical, and appropriate  radiographs, the physician can reach a working diagnosis of the lesion. Although  benign and malignant tumors can mimic each other, some tumors can be ruled out  on the basis of the history, the age of the patient, the location of the tumor  (in which bone and where in the bone), and the radiographic appearance of the  tumor, as shown in Tables 6-1, 6-2, 6-3, 6-4, 6-5, and 6-6. For example, a  20-year-old man with a 3-month history of pain in the knee is found to have an  epiphyseal lesion in the distal femur. The lesion has a benign geographic  appearance. If the tumor is benign, the criteria of the patient's age (see Table  6–2) eliminates only solitary bone cyst and osteofibrous dysplasia, but all  other benign tumors remain possibilities. If the tumor is malignant, it is  likely to be an osteosarcoma (various types), Ewing sarcoma, fibrosarcoma,  vascular sarcoma, or, possibly, chondrosarcoma, according to the age criterion.  The most common site for bone tumors is about the knee, especially the distal  femur. The likely benign tumors are giant cell tumor, nonossifying fibroma,  chondroma, osteochondroma, and chondroblastoma. The likely malignant tumors in  this age group are osteosarcoma, Ewing sarcoma, fibrosarcoma, and, possibly,  chondrosarcoma. Most malignant tumors are metaphyseal. Based on location in the  bone (Table 6–4), the most likely benign tumors are chondroblastoma and giant  cell tumor. Most malignant tumors are metaphyseal. The geographic appearance  implies a benign radiographic appearance. Thus, the working diagnosis would be  chondroblastoma or, possibly, giant cell tumor if the lesion were benign,  whereas it would be osteosarcoma or chondrosarcoma if the lesion were malignant,  which is less likely. In this age group, metastatic disease is very unlikely,  but low-grade infection may mimic a tumor, particularly if the patient is  immunocompromised, as can be determined from the patient's history. Table 6–5  indicates the most useful studies for further workup.         Table 6–4. Skeletal Distribution of Bone Tumors, Ranked from  Most Common (1) to Less Common (5) Sites.Type of Tumor Femur Tibia Foot or Ankle Humerus Radius Ulna Hand or Wrist Scapula Clavicle Rib Vertebra Sacrum Pelvis Skull Face   Imaging  Characteristics Location in a Long  Bone Beneficial  Studies  Type of Tumor Geographic Moth Eaten Permeative Epiphyseal Metaphyseal Metadiaphyseal Diaphyseal Surface Plain Radiograph CT Scan MRI Isotope Bone Scan Blood  Studies   Benign bone   MFH = malignant fibrous  histiocytoma. Isotope Bone Scanning Technetium-99 radioisotope scans are used to assess the  degree of osteoblastic activity of a given lesion (Figure 6–4). In general, they  are quite sensitive, with a few exceptions, for active lesions of bone.  Accordingly, technetium-99 scans are excellent screening tools for remote  lesions (staging). The best indication for a bone scan is suspected multiple  bony lesions, such as those commonly seen in metastatic carcinomas and lymphomas  of bone. Isotope bone scanning is far simpler to perform, less expensive, and  requires less total body irradiation than skeletal surveys. It is common  practice to use serial isotope scans to follow patients with suspected  metastatic disease and at the same time evaluate the effectiveness of their  systemic therapy program.             <img src="http://www.elakiri.com/forum/Print%20Chapter%206_%20Musculoskeletal%20Oncology_files/loadBinaryCAB9Z600.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" /><img src="http://www.elakiri.com/forum/Print%20Chapter%206_%20Musculoskeletal%20Oncology_files/loadBinaryCAB9Z600.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" /></blockquote>

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