MC is a 13-year-old girl whose right knee pain had been getting worse over several months. She did not recall any particular trauma or injury though she is an active young girl and avid dancer. Her pain was worse with activity and also present at night. She noted swelling on the lateral side of her knee without bruising or other skin changes. She had no significant past medical history.
On examination, MC had tenderness to palpation over the right lateral femoral condyle with an associated area of swelling. Her strength and sensory examination of the right leg was normal. She lacked 10 degrees of right knee flexion compared to the opposite side. Her gait demonstrated a slight limp on the right.
Plain radiographic examination revealed a mixed osteolytic (bone destroying) and osteoblastic (bone producing) lesion in the right distal femoral metaphysis (see Figure 2). An MRI scan better delineated a lesion in the distal femur with a small soft tissue mass adjacent to the bone lesion (see Figures 3A and 3B).
Figure 2: X-ray shows a destructive lesion in the lateral distal femur, just proximal to the growth plate. Note both bone formation (solid arrow) and destruction (dotted arrow).
Figure 3A and 3B: MRI scan in coronal (3A) and cross (3B) sections better define the area noted on the X-ray with a small soft tissue mass lateral to the femur.
Figure 4: Postoperative X-ray shows the distal femoral prosthesis and knee replacement that replaces the segment where the osteosarcoma was removed.
An image-guided needle biopsy revealed tissue consistent with a high-grade osteosarcoma. Staging studies revealed no evidence of metastasis. MC was treated with preoperative chemotherapy at the CHOP Cancer Center on a national cooperative group protocol. After the first cycle of chemotherapy, her pain completely resolved and there was resolution of the mass along the lateral knee. She had a limb-sparing surgery 3 months after diagnosis with removal of the distal femoral osteosarcoma and reconstruction with a metal knee replacement (see Figure 4). The knee replacement is much more extensive than a similar reconstruction performed for osteoarthritis in older patients. Since MC was already post-menarche, she did not need a special growing device, which is available for younger patients. She is now receiving additional chemotherapy as part of the standard protocol. The resected tumor was studied by the CHOP musculoskeletal pathology team and found to be 98% dead, which predicts a good prognosis for MC’s overall survival.
MC’s case illustrates a typical presentation of a child with a primary bone malignancy. The most common presenting symptom is pain due to bone destruction with or without an accompanying soft tissue mass. Patients with malignant bone tumors should be diagnosed as soon as possible, although it is important to remember that sports injuries are substantially more common than cancer in this age group. Although osteosarcoma is the most common malignant bone tumor in children, it remains quite uncommon (approximately 1000 patients per year in the United States).
Patients who have pain associated with injury or overuse should be managed initially with symptomatic treatment such as activity modification, ice or heat, nonsteroidal anti-inflammatory drugs and/ or physical therapy. These interventions will allow the vast majority of patients to heal and return to activities.
Initiate further workup if symptoms persist. Concerning signs include: worsening pain unrelieved by nonsteroidal anti-inflammatory drugs, pain at rest or at night, worsening limp or joint range of motion, and increasing (or not decreasing) soft tissue swelling or mass.
The first imaging study should be plain radiographs. If negative, it is reassuring that there is not a fracture or tumor. However, if symptoms persist or there is swelling or a soft tissue mass, an MRI scan should be performed to identify both marrow-replacing lesions that have not caused enough bone destruction to be visualized on plain radiographs, as well as soft tissue masses. It also helps to evaluate the adjacent growth plate, articular cartilage, and joint.
Imaging studies showing a benign lesion unrelated to the pain from the recent injury are best evaluated by a physician experienced in recognizing these benign bone and soft tissue lesions. If imaging studies show a lesion that is indeterminate, a biopsy may be required. At CHOP, image-guided needle biopsies or minimally invasive techniques are used in all cases. Bone and soft tissue lesions in children are uncommon, so an experienced musculoskeletal pathologist is necessary to make an accurate diagnosis.
Malignant bone and soft tissue tumors in children require multidisciplinary evaluation and treatment best performed at a center with experience with these rare lesions. CHOP has a highly experienced and cohesive team of orthopedic oncologists, pediatric oncologists, radiation oncologists, and musculoskeletal radiologists/pathologists, along with core nursing, child life, and physical therapy services. If you see a child in your practice with a bone or soft tissue lesion, we are happy to evaluate him or her immediately and communicate back to you.
Co-author Alex Arkader, MD, will join CHOP’s Division of Orthopedics on August 8, 2015.
References and Suggested Readings
Weber KL, Peabody T, Frassica FJ, et al. Tumors for the general orthopedist: how to save your patients and practice. Instr Course Lect. 2010;59:579-591.
Arndt CA, Rose PS, Folpe AL, et al. Common musculoskeletal tumors of childhood and adolescence. Mayo Clin Proc. 2012;87(5):475-487.
Frances JM, Morris CD, Arkader A, et al. What is quality of life in children with bone sarcoma? Clin Orthop Relat Res. 2007;459:34-39.