The initial work-up of and the evaluation of a bone tumor can be a confusing and complicated process. This learning module spells out a systematic approach to the problem.
The initial evaluation of a bone tumor begins with two high quality orthoganal radiographs. Based on your evaluation of these, you will then categorize the lesion as good, bad or ugly -- or more precisely -- as latent, active or aggressive. This distinction is based on a few simple criteria that this learning module will review. Once you have decided which category the lesion belongs to, the rest of the work-up follows easily. Each category of lesion gets its own type of work-up.
The initial work-up of and the evaluation of a bone tumor can be a confusing and complicated process. To help simplify this process, I recommend that your first step be to get two high quality plain radiographs. Based on your evaluation of these you will be able categorize the lesion as good, bad or ugly -- or more precisely -- as latent, active or aggressive. This distinction is based on a few simple criteria that are easily seen on plain radiographs. Once you have decided which category the lesion belongs to, the rest of the work-up follows easily. Each category of lesion gets its own type of work-up, which will be covered in part II. Categorizing bone lesions in this way will help you avoid unnecessary and expensive work-ups in some cases and errors and delays in other cases.
To begin, you need two high quality plain radiographs of the lesion. To manage tumors in this way, you need to look at the radiographs yourself. If you are not set up in your practice to examine the xray films yourself, than you should consider sending the actual films or digital images to an orthopedic oncologist or a radiologist with musculoskeletal tumor experience. Since these tumors are rare, involving someone with true expertise in this area right from the very start will save a lot of time and trouble. (See sending cases to the bonetumor.org team. ) If the films are more than 10 days old, get new films. Your assessment needs to be made based on the lesion's appearance now, not some time in the past. If the films are of mediocre quality, get new films. For the purposes of this evaluation, you need the best views of the lesion you can get.
You need to assess three things: The margin, the periosteal reaction, and the soft tissue mass. The margin is the edge of the tumor where it meets the surrounding bone. To keep things simple, we'll say a margin can be narrow, broad, or poorly defined. You want to visually assess how much distance there is at the edge of the tumor between the area that is clearly tumor, and the area that is clearly normal, undamaged, uninvolved bone. If the tumor and the surrounding normal bone are literally right next to each other and touching, and you see a very small distance between them, you are looking at a narrow margin. A narrow margin is as narrow as pencil line, perhaps 0.1 to 1.0 millimeters. If the tumor has a narrow margin, you can usually take a pencil and draw a line around the exact outline of the lesion - it's that distinct. In a tumor with a broad margin, you might be able to draw a line around the outside of the tumor, but you would need a thick magic marker to do it. You can see where the tumor is, and you can see where there is undamaged bone, but in between the two there is an area that is indistinct that looks like it might be partially damaged. This constitutes a broad margin. A broad margin is usually at least 2 millimeters and may be 8 - 10 millimeters. A poorly defined margin is one where you can tell that there is a tumor in the bone, and there are areas that are distinctly abnormal, but you just can't tell how big the lesion is or where it begins or ends. A poorly defined margin will give you a vague impression thet you see a tumor - and that vague impression is a bad sign. You may see multiple small holes in the bone that are called a "moth-eaten" pattern, or the holes may be so small they run together into a "permeative" pattern. Both these patterns are signs of a poorly defined margin. A poorly defined margin may be as wide as several centimeters or it may be impossible to actually measure the margin. Some tumors have areas of narrow margins and other areas that are not as well defined. As a rule of thumb, to be called narrow, about 80% of the margin should meet the criteria above. On the other hand, if you see any area of the margin that is clearly poorly defined, then the whole margin should be called poorly defined.
The next feature to assess is the periosteal reaction. This is reactive, new bone formation outside the normal cortical boundries of the bone. The periosteal reaction can take on a wide variety of appearances, but for our purposes, we need only to decide if the perioseal reaction is absent, mild, or major. Clearly, if there is no periosteal reaction, you can move on th the next step. A mild periosteal reaction consists of one layer, normally 1 to 4 millimeters thick, which lies adjacent to the cortex. A major periosteal reaction may be thicker than 5 mms., multilayered (lamellated), or it may have a "sunburst" or "hair on end" pattern.
Finally you want to assess any soft tissue mass. Remember, you are still looking at a plain radiograph, not a CT or an MRI. If a soft tissue mass is present around a bone tumor, you will be able to see it on good quality plain radiographs. You simply need to decide if there is a soft tissue mass or not. That's it!
Now use the information you have and the table below to decide what sort of tumor you are dealing with. If you go through this process two or three times, you won't need to use the table, since it's pretty intuitive.
| Margin | Periosteal Reaction | Soft Tissue Mass | |
| Latent | Narrow | None | Absent |
| Active | Wide | None or Mild | Absent |
| Aggressive | Wide or Poorly Defined | Mild or Major | Present |
Latent lesions are just that - they are probably sitting there doing nothing. If any concern exists, a basic work - up including a CBC with differential and a bone scan is done. For a latent lesion which is causing the patient no trouble, no further work-up is needed at the time of presentation. In any case the lesion should be observed with radiographs at intervals, say 3 - 6 months, to check for any change or growth. After one to two years of observation without any change, the lesion may be safely ignored.
Active lesions demand attention. They need a focused work-up, and likely a biopsy and treatment as well. In addition to the two new radiographs you just got, I recommend an MRI of the lesion and the surrounding anatomic structures, a whole body technecium bone scan, and basic labs including a CBC with differential and an erythrocyte sedimentation rate. Further work up may be required based on the nature of the lesion, the age and health history of the patient, and other factors, but the basic work-up remains the same.
Aggressive lesions demand immediate attention, but the biosy must be performed as the last step. Most aggressive lesions are due to malignant primary or metastatic tumor, although a few may be benign. They require a complete and prompt work -up which will also serve as a staging work - up for cancer. In addition to the focused work - up above (Xrays, bone scan, MRI), a CT scan of the chest is required, as well as a complete panel of labs. I often begin with a CBC with differential, ESR, elecrolytes, LFT's, Ca++ and Alkaline Phosphatase, and LDH. Other more specialized labs are likely to be required. For probable metastatic lesions where the primary is unknown, a CT scan of the abdomen and pelvis is obtained in addition to the CT of the chest.
Remember, the biopsy is the last step. Most tumor specialists recommend that the biopsy be performed by the person or team who will be performing the definitive surgery. Consider carefully before you dive into these murky waters. The complete treatment of an aggressive bone tumor requires an experienced team, including a bone pathologist, musculoskeletal radiologist, medical oncologist, radiation oncologist, orthopedic oncologist, plastic surgeon, clinical psychologist, as well as all the ancillary services they rely on. Patients with these lesions are better off getting their care at a tumor center right from the beginning. The orthopedic surgeon considering the work - up and care of a patient with a potential bone tumor should rely on his or her judgement in deciding which patients need referral to a tumor specialist. Some cases clearly need a referral, but others may be borderline. One possible approach is to mail the films and other results to an orthopedic oncologist for review. That way all bases are covered, and both the physician and the patient will feel more confident. Images sent by e-mail are sometimes adequate for these purposes, if they are of very high quality.
