Differential Diagnosis
In addition to osteochondromas, several other lesions should be considered in the patient with musculoskeletal lesions (see Table 15,6,13-19).
Cartilaginous tumors. Chondrosarcomas are malignant cartilaginous tumors.20-22 They commonly affect long bones, including the humerus and femur, and some flat bones, such as the pelvic bones.13,22 They are most commonly seen in adults, and have no predisposition by gender.13
Chondrosarcomas can be primary (ie, arising de novo) or secondary (developing on preexisting benign cartilaginous neoplasms, including osteochondromas). The majority of chondrosarcomas are slow growing, and they rarely metastasize. It is difficult to differentiate between a benign lesion (such as an osteochondroma) and a chondrosarcoma by either histology or radiology. However, reliable predictors for malignancy include size exceeding 5 cm and location in the axial skeleton.20
Bone tumors.Osteosarcomas are the most common malignant bone tumors in children and adolescents, with 400 to 560 US patients in this age-group diagnosed each year.14-16 Osteosarcomas are uncommon in children younger than 10; their incidence peaks during the early teenage years (median peak age, 16), then declines rapidly among older patients. They are more common in males than females.15
Osteosarcomas commonly develop during periods of rapid bone turnover, such as the adolescent growth spurt. Common sites include the distal femur, proximal humerus, and proximal tibia,15,16 particularly near the knee.13 Usually, osteosarcomas present with nonspecific symptoms, including strain-related pain of several months’ duration, which may disrupt sleep.16 Laboratory findings in affected patients may include elevations in LDH, alkaline phosphatase, and/or ESR.15,23
Physical exam reveals a visible or palpable mass in the affected area, along with decreased joint motion; localized warmth or erythema may also be present. Late signs of osteosarcoma include weight loss, general malaise, and fever. First-line imaging for the patient with a suspected osteosarcoma is x-ray, which will show ill-defined borders, osteoblastic and/or osteolytic features, and an associated soft tissue mass. Advanced imaging, such as MRI, is warranted.16
Ewing sarcoma, the second most common bone tumor in children and adolescents, is an aggressive form of childhood cancer.14,18 Approximately 25% of all Ewing sarcomas arise in soft tissues rather than bones.18 They are more common in whites than in other ethnic groups and have a slight male predominance.13,18 The median age at diagnosis is 15.13 The most common presenting symptoms are tumor related, such as pain or a noticeable mass. While x-rays are usually ordered first, MRI is preferred.18
Soft tissue tumors and masses.Rhabdomyosarcomas are malignancies that account for more than half of the soft tissue sarcomas in children and adolescents. Less than one-fifth of cases occur in the extremities, and most occur in children younger than 10. These lesions have a slight male predominance and are more common in whites than in other patients.14,17,24
Approximately 6% of childhood soft tissue tumors are adipose tissue tumors, which may be benign (eg, lipomas) or malignant (eg, liposarcomas). Lipomas in children account for nearly 4% of all soft tissue tumors and can be classified as superficial (which are often diagnosed clinically) or deep (frequently requiring imaging).25
Lymphomaaccounts for 7% of cancers in US children and adolescents and more than 25% of newly diagnosed cancers in patients between 15 and 19, making it the most common malignancy in adolescents and the third most common in children.26,27 Non-Hodgkin lymphoma is the fourth leading type of malignancy in US adolescents.27 Rarely, lymphomas present with primary event soft tissue involvement.28
Myositis ossificans (MO) is a rare benign disorder involving formation of heterotrophic bone in skeletal muscles and soft tissues.29 Though possible in patients of any age, MO is most commonly seen in adolescents and young adults. Often the result of soft tissue injury (in which case it is referred to as myositis ossificans circumscripta or traumatic), MO develops in areas that are exposed to trauma, such as the anterior thighs or arms. Lesions can be diagnosed via plain x-ray or CT, although MRI and ultrasound can also be useful evaluation tools.17,29,30
Because MO circumscripta typically presents as a painful soft tissue mass, it can be mistaken for a soft tissue sarcoma or an osteosarcoma; radiologic evaluation is required to make the proper diagnosis. Less common forms of MO are myositis ossificans progressiva and myositis ossificans without a history of trauma.29
Ollier diseaseis a rare, nonfamilial disorder characterized by multiple enchondromas (or enchondromatoses), which are distributed asymmetrically with areas of dysplastic cartilage. Enchondromas are benign cartilage tumors that frequently affect long tubular bones along the metaphyses in proximity to the growth plate. The enchondromas result in significant growth abnormalities. About one in 1 million people are diagnosed yearly.5,19 (Similarly, Maffucci syndrome is represented by multiple enchondromas in association with hemangiomas.5)
Ollier disease typically manifests during childhood5 with bone swelling, local pain, and palpable bony masses, which are often associated with bone deformities.19 Patients generally present with an asymmetric shortening of one extremity and the appearance of palpable bony masses on their fingers or toes, which may or may not be associated with pathologic fractures.5,19 In 20% to 50% of patients with Ollier disease, enchondromas are at risk for malignant transformation into chondrosarcomas.5
Vascular malformations. Certain abnormalities of vascular development cause birthmarks and abnormalities of varying degree in underlying tissues.31 They are usually present at birth and grow proportionally to the child’s growth.25,31 However, they can also be seen in later childhood and adolescence.