Tumors

Alexandre Arkader, MD

John M. (Jack) Flynn, MD

Kristy L. Weber, MD¹

¹Guru:

General Considerations

Rule number 1 of medicine is “Do no harm,” and rule number 1 of orthopaedic oncology should be “Be aware of the zebras.” While bone and soft tissue tumors are rare conditions, in particular in children, they will find you regardless of what your subspecialty interest may be. The incidence of cancer in the United States for 2018 was around 1.7 million. There were approximately 3500 new cases of bone and soft tissue malignant tumors, corresponding to 0.2% of the total, and only 25% of these were in patients younger than 20 years.¹ So you may ask yourself, why do I need to know about something so uncommon? Because orthopaedic surgeons are usually the first line of defense after pediatricians and primary care physicians for evaluation of these lesions. Furthermore, benign conditions are at least 10 times as common as malignancies. Therefore, in order to stay out of trouble, one should be comfortable diagnosing and managing the most common benign conditions, but at the same time comfortably recognize the “imitators”, the “no touch” lesions and malignancies, avoiding burning bridges and impacting prognosis in a negative way. While the goal of this chapter is not to provide detailed comprehensive management of musculoskeletal tumors, we will review the basic principles and highlight areas of “caution” when evaluating one of these lesions.

Making the Diagnosis

HISTORY AND PHYSICAL EXAMINATION

Play the detective: obtaining a complete history is important and may provide clues for appropriate differential diagnosis. The main things to inquiry about are family history of systemic conditions, lesions, or tumors; past medical history, including presence of diagnosis such as metabolic diseases, previous infections, etc.; environmental factors exposure; prodromal symptoms such as pain, fever, or others; history of repetitive or acute trauma.

Typical Scenarios of How a Bone or Soft Tissue Tumor May Present

Incidental: When a patient is getting an imaging examination for an unrelated condition, or acute trauma and a lesion is noted.
Pain: Pain is the most common presenting symptom. While some tumors have a characteristic pain pattern, such as osteoid osteoma, with pain at night alleviated with nonsteroidal anti-inflammatory drugs (NSAIDs), most lesions don’t display a typical pattern.

ORTHOPAEDICS 101: Classic “red-flag” symptoms that should raise awareness of treating physician are pain that wakes children from sound sleep, pain resistant to regular analgesics, and pain that has no relationship with the type of physical activity exerted throughout the day.
Limp: Abnormal gait or limp can be the only presenting sign of a tumor. This is particularly true for younger children, who often will adapt or modify their gait pattern, rather than complain of discomfort. Limp without a witnessed trauma should be met with high level of suspicion.
Mass: This is one of the most objective signs of a tumor, but imitators such as infection, heterotopic ossification, and others may present in a similar fashion. In the case of soft tissue masses, the ability to move the mass from deep planes can help differentiate deep seated, large and adherent malignant lesions from the more superficial, small, and benign ones. Size also matters, as soft tissue lesions larger than 5 cm are very suspicious for a malignancy, especially if seated deep to the fascia. Transillumination of superficial masses is an easy and quick way to diagnose cystic lesions such as ganglion or popliteal cysts. Nothing is more telling about a palpable mass than its behavior.
Painless mass: While painless masses are more often benign in nature, the absence of pain does not eliminate a possible malignant diagnosis. The classic example is synovial sarcoma, which can be present for years prior to causing any discomfort or rapidly growing.

ORTHOPAEDICS 101: Synovial sarcomas are tumors that can be stable in size for quite a while before demonstrating their aggressive nature, with rapid growth pattern. They are the most common soft tissue tumor of the foot and between ages 20 and 40 years.

Figure 19-1 This is an 8-year-old boy with a diagnosis of McCune Albright syndrome. Note the large café-au-lait spot over the left chest and abdominal area. (Used with permission of CHOP Orthopedics, Philadelphia, PA.)

Understanding the behavior of a lesion is a key factor in determining its aggressiveness and urgency in which referral or treatment is needed. While it may be difficult to make that determination at first encounter, there are a few questions that can help you get there. These include the length of symptoms or presence of a palpable mass and its rate of growth, changes, or associated symptoms. In general, lesions that have been latent (stable in size) for several months or years are more likely to be slow growing and benign, while lesions that grow in a rapid and continuous fashion indicate an active process that is more suspicious for malignancy.

It is imperative that while examining a patient with a bone or soft tissue mass, the entire extremity is examined for the presence of enlarged nodes, skin changes, altered range of motion (due to mass effect or pain), and changes in neurovascular status. Skin changes, for example, can suggest a systemic condition or a nontumor diagnosis, such as a vascular malformation, or a syndromic diagnosis such as neurofibromatosis or McCune Albright (Fig. 19-1).

IMAGING

Radiographs are the single most useful imaging modality for diagnosis of bone lesions; it should be seen as the stethoscope of the orthopaedist. MRI is the gold standard for soft tissue lesions and is also very helpful for bone lesions.

The indications for CT are limited due to the concern of ionizing radiation, but it is still the best tool to identify osteoid osteomas and helpful to rule out pathologic fractures, as well as a preoperative planning tool for certain lesion associated with angular deformities such as fibrous dysplasia (Fig. 19-2) or unicameral bone cyst (UBC), by 3D reconstruction of models.

Figure 19-2 A: Right proximal femur 3D CT Recon of a child with fibrous dysplasia and shepherd’s crook deformity. B: 3D-printed model of the deformity for preoperative planning. (Used with permission of CHOP Orthopedics, Philadelphia, PA.)

TABLE 19-1 Stepwise Approach to Radiographs

1.	Tumor location	What bone Where in the bone Central versus eccentric
2.	Tumor effect on bone	Margins Type of lesion Matrix
3.	Bone reaction	Cortical changes Periosteum
4.	Associated findings	Pathologic fracture Soft tissue mass Interval progression Multiple or second lesion

TABLE 19-2 Key Differential Radiographic Findings to Stay Out of Trouble

Benign Tumors

Malignant Tumors

Well-defined

Continuous periosteal reaction

Bone remodeling

Solitary lesion (with exceptions^a)

No soft tissue mass

Permeative

Destructive

Cortical breakthrough (with exceptions^b)

Disorganized periosteal reaction

Multiple lesions (with exceptions^a)

Soft tissue mass

^aMultiple osteochondromas, fibrous dysplasia, enchondromatosis.

^bBenign lesions: nonossifying fibroma, aneurysmal bone cyst.

Radiograph assessment should be approached in a stepwise manner to facilitate generating a differential diagnosis (Table 19-1) and therefore staying out of trouble (Table 19-2).

Tumor Location

Most tumors have a predilection for the metaphyseal regions of long bones, especially during the growing years. In general, a short differential list can be generated based on location alone, for example, lesions in the posterior elements of the spine are usually benign (e.g., aneurysmal bone cyst, osteoid osteoma, and osteoblastoma), epiphyseal lesions differential is usually limited to chondroblastoma, Brodie abscess, or giant cell tumor. While common central lesions include UBC and enchondroma, eccentric lesion examples include aneurysmal bone cyst and nonossifying fibroma. NEWSFLASH! In the metaphysis “anything can be anything,” as this is the most common area for development of bone lesions.

Effect on Bone

Rapidly growing and aggressive lesions will permeate the bone in a way that it is difficult to determine lesion boundaries. These lesions can at time lead to complete bone destruction and pathologic fractures.

Bone Reaction

If the lesion is not aggressive or if it has been present for a long time, the bone is able to adapt and “protect” itself, producing organized periosteal reactions, cortical thickening, expansion, etc. On the other hand, very slow growing benign lesions such as UBC or fibrous dysplasia can overtime lead to cortical thinning, with minimal bone response (Fig. 19-3).

Associated Findings

There are several red flag signs of a malignant or aggressive lesion, and those need to be readily recognized. They include but are not limited to cortical destruction, soft tissue mass, satellite lesions, etc. ORTHOPAEDICS 101: Be attentive to the possibility of axial tumors, these lesions are often very difficult to visualize on radiographs, and low threshold for advanced imaging is recommended (Fig. 19-4).

BIOPSY

While most pediatric orthopaedists will not routinely treat tumors, it is almost certain that they will encounter these lesions in their practice at some point. The key to staying out of trouble is to understand which lesions should and shouldn’t
be biopsied by a generalist and how to safely and efficiently perform a biopsy. The Musculoskeletal Tumor Society (MSTS) has reported on the hazards of a poorly performed biopsy in two different occasions.² The inability to perform an adequate biopsy can lead to worse outcome, need for further procedures, and otherwise unnecessary amputations.

Figure 19-3 Radiographs of right proximal humerus in a 7-year-old boy, demonstrating a well-defined, lytic lesion in the meta-diaphysis. There is mild expansion and septation; there is no soft tissue mass, cortical disruption, or periosteal reaction. The lesion was consistent with an aneurysmal bone cyst. (Used with permission of CHOP Orthopedics, Philadelphia, PA.)

Figure 19-4 A: AP pelvis radiograph of a 12-year-old boy with a history of bilateral valgus slips, complaining of pain in the right hip. The arrow points to an area of increased sclerosis at the sacroiliac (SI) joint region. Sagittal (B) and axial (C) T2-weighted MRI demonstrates a bone forming lesion with an associated large soft tissue mass, expanding into the sciatic notch, sacroiliac, and sacral involvement of this osteosarcoma. (Used with permission of CHOP Orthopedics, Philadelphia, PA.)

Figure 19-5 A: AP femur radiograph of a 3-year-old boy who presented with a limp. Note the subtle, but well-defined lytic lesion in the proximal metaphysis and diaphysis. B: T1-weighted coronal MRI demonstrates intramedullary marrow involvement and no soft tissue mass. The final diagnosis was Ewing sarcoma. (Used with permission of CHOP Orthopedics, Philadelphia, PA.)

After a patient with a bone or soft tissue lesion is evaluated in clinic, the treating physician needs to make sure that all necessary imaging studies are adequately completed and a differential diagnosis is formulated. The next step is to determine the urgency in which the biopsy/diagnosis needs to be made: the next 24 hours, the next few days, or the next few weeks. If there is a concern of a malignant or aggressive process, adequate referral to a tertiary center may be preferred over performing a biopsy.

While open incisional biopsy has been the standard of care for decades, most tertiary centers have moved toward image-guided needle biopsies in conjunction with interventional radiology. Percutaneous methods of biopsy, core needle in particular, are safe, less invasive, and less costly and avoid several risks associated to open biopsies such as infection, need for biopsy tract resection, pathologic fractures, etc. and have been shown to provide similar accuracy of diagnosis.³ If an infectious process is in the differential diagnosis, culture and sensitivity should be sent at time of biopsy. ORTHOPAEDICS 101: “Biopsy every culture and culture every biopsy” is a principle that should be followed, as several neoplastic processes may present in a very similar fashion as an infection. Ewing sarcoma, in particular, can resemble a low-grade infectious process on imaging and clinical presentation, including elevated inflammatory markers (Fig. 19-5).

Benign Bone Tumors That Every Orthopaedist Should Know

UNICAMERAL BONE CYST

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