Fig. 1 Radiograph of the starburst pattern of ossification (A) and a cross-sectional CT (B) of a patient with osteosarcoma of the distal femur. Reproduced from Hornicek F: Osteosarcoma of Bone, in Schwartz H (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors, ed. 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2007, p 164.

AAOS Now

Published 8/1/2008
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Annie Hayashi

Staying out of trouble with tumors

Musculoskeletal oncologists offer important guidance for nontumor surgeons

“Patients who have bone and soft-tissue lesions present challenges to the practicing orthopaedic surgeon,” said Theodore W. Parsons III, MD. “Treating these patients can be anxiety-provoking for the surgeon—as well as the patient—with the looming question being whether the lesion is malignant or benign.”

Dr. Parsons, along with musculoskeletal oncologists Kristy L. Weber, MD, Denis R. Clohisy, MD, and Frank J. Frassica, MD, offered advice on evaluating and managing lesions to avoid common errors at a symposium held during the 2008 AAOS Annual Meeting.

Errors include delayed diagnosis, misdiagnosis, and inappropriate removal of malignancies.

“Good” and “bad” lesions on imaging studies
A systematic process is helpful when evaluating an unknown lesion, according to Dr. Parsons. “Start with good quality, biplanar radiographs—the ‘gold standard’ for evaluating bone lesions,” he advised. “These should provide significant information about the lesion.” (For tips on what to look for, see “Tumors: Clues to identification” below.)

If information from a conventional radiograph is not sufficient, Dr. Parsons recommends bone scintigraphy (BS) or other more advanced studies—a computed tomography (CT) scan, a magnetic resonance imaging (MRI) scan or even a positron emission tomography (PET) scan.

“BS helps determines whether a bone lesion is active or indolent and can identify radiographically occult lesions,” he explained. “CT scans can detect mineral density in subtle lesions, identify cortical integrity, or evaluate axial skeletal lesions in the pelvis and the spine where the bony anatomy is complex.”

Dr. Parsons believes MRI is “a superior modality for imaging soft-tissue lesions.” He encourages orthopaedic surgeons to understand the “basic tenets of imaging” instead of relying on the radiologist to “make the call.”

When assessing tissue metabolism and tumor physiologic activity, PET and PET CT scans can be useful.

“Careful evaluation of the patient and imaging studies can generally guide the clinician to an accurate differential diagnosis,” he said.

“Comparing plain radiographs to the other studies will assist in identifying lesions that should be referred to a tumor surgeon, as well as those simple, benign lesions that may be observed.

“When in doubt about a lesion, it is always wise to refer,” he concluded.

Staying out of trouble: The older patient
Many conditions may result in destructive bone lesions, but “in patients older than age 40, the most common diagnosis is metastatic carcinoma,” explained Dr. Weber, “though primary malignant bone tumors do occur.”

Metastatic bone disease comes from two primary areas—the breast and prostate—and, to a lesser degree, from the lung, kidney, or thyroid.

“Treatments for metastatic bone disease and primary malignant bone tumors are very different,” she emphasized. She advised taking a careful, stepwise approach to evaluating the patient’s lesion before deciding on a course of action.

Clinical evaluations should include a complete history, physical examination, lab studies, and radiographs. “Always ask patients if they have ever had cancer,” she advised.

“If plain radiographs don’t give you enough information to make a definitive diagnosis, consider doing a bone scan or a CT scan of the chest, abdomen, and pelvis.

“If you don’t find a primary lesion, do not assume it is a metatasis based on the patient’s history and imaging alone. A biopsy should be done if you still have questions about the diagnosis,” she said.

Fig. 1 Radiograph of the starburst pattern of ossification (A) and a cross-sectional CT (B) of a patient with osteosarcoma of the distal femur. Reproduced from Hornicek F: Osteosarcoma of Bone, in Schwartz H (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors, ed. 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2007, p 164.
Fig. 2 (A) AP radiograph of the right proximal tibia of a 14-year-old boy shows a well-circumscribed lytic lesion in the epiphysis extending into the metaphysis, a typical location for a chondroblastoma. (B) A CT scan better defines the lesion located in the posterior aspect of the proximal tibia. Note the sclerotic border and mineralization within the lesion. Reproduced from Weber K, O’Connor M: Benign Cartilage Tumors, in Schwartz H (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors, ed. 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2007, p 115.

Dr. Weber emphasized that moving forward without a complete and accurate diagnosis can have dire consequences.

“Placing an intramedullary device in a 65-year-old patient who has a lytic lesion in the femur without thorough evaluation is dangerous. If the patient has a dedifferentiated chondrosarcoma, that reamer will just spread those cancer cells up and down the femur,” she said.

Staying out of trouble: The child
“When children have sarcomas, orthopaedic surgeons need to talk to the child and the parents, as well as conduct a careful history and a physical examination that includes undressing the child and examining the affected part of the body,” said Dr. Clohisy.

“An orthopaedic surgeon could suspect the presence of a childhood bone malignancy based on clinical history and symptoms alone. In patients without a pathologic fracture, any positive finding during the physical exam—limb swelling, loss of motion, weakness, a mass—should raise concerns about a possible malignancy,” he explained.

In children, pain that is not related to an activity may be a symptom of bone cancer. A child who is in constant, increasing, or severe pain or awakens at night due to pain should be evaluated.

“Lesions with a soft-tissue mass should be assumed malignant until proven otherwise by biopsy. Large lesions on radiograph, greater than 4 cm, are also often malignant,” he said.

Dr. Clohisy recommends doing a biopsy if the orthopaedist is not completely certain that the tumor is benign. He also strongly suggests that no surgical treatment be performed until a diagnosis has been confirmed by a biopsy. If a malignancy is suspected, a biopsy must be done.

Staying out of trouble: Soft-tissue masses
The two major errors when diagnosing soft-tissue sarcomas are inappropriate excisional biopsy and delayed diagnosis according to the literature.

To avoid these errors, Dr. Frassica recommends the orthopaedist “knows the clues to the presentation of a soft-tissue sarcoma, orders the correct tests, and makes the appropriate decisions.”

“The challenge is to analyze the radiographs, the MRIs, and then choose the next correct step—observation, incisional needle biopsy, or excisional biopsy.

“Do not delay in making a diagnosis, even if you initially choose to observe,” he cautioned. “Malignancies must be identified as early as possible.

“The MRI scan should be analyzed by the radiologist and the orthopaedist. A lesion that can be identified, such as a lipoma, a ganglion, or a hemangioma—can be managed without a biopsy,” explained Dr. Frassica.

“If we look at the MRI ourselves or with the radiologist and we cannot tell what the mass is, we classify it as ‘indeterminate.’ All masses that are ‘indeterminate’ require a biopsy.”

Prior to performing the biopsy, Dr. Frassica advises reviewing the imaging studies with an experienced radiologist and pathologist. “The MRI signal sequences are very complex at times, and the clinical expertise can be valuable.”

“If you are unsure or have questions, get a second opinion or refer the patient to a musculoskeletal oncologist,” he concluded.

Annie Hayashi is the senior science writer for AAOS Now. She can be reached at hayashi@aaos.org

Tumors: Clues to identification
Periosteal patterns help determine the aggressiveness of a lesion.

  • Solid, smooth periosteal new bone results from slow-growing lesions or chronic periosteal irritation.
  • Lamellated (‘onion skin’) or spiculated (‘sun burst’) patterns (Fig. 1)are classically noted in Ewing’s sarcoma and osteosarcoma,
  • respectively
  • Codman’s Triangle (elevated edge of periosteum) reflects rapid cortical invasion, with peripheral detachment and central destruction of the periosteum.

Location of the lesion helps establish the diagnosis.

  • Chondroblastomas and giant cell tumors typically occur in the epiphyses or apophyses of long bones (Fig. 2).
  • Osteofibrous dysplasia and adamantinoma are classically tibial lesions.
  • Nonossifying fibromas are eccentric, marginated metaphyseal lesions of long bones with cortical involvement.
  • Simple bone cysts are centrally located, typically in the proximal humerus or femur.

Matrix mineralization is a helpful diagnostic clue.

  • Stippled or “arc and ring” calcifications indicate a chondroid tumor.
  • Amorphous, “cloudlike” mineralization is typical of osteosarcoma or blastic metastases such as prostate carcinoma.
  • Fibrous dysplasia typically demonstrates a “ground-glass” appearance.
  • Bone infarcts often reveal a swirling, “smoke up the chimney” mineralized pattern.