Osteochondroma

For 9 years, an asymptomatic mass had been present on the right side of the back of a 49-year-old man. He had never had any pain in the region and had no limitation of motion of the right shoulder.

An initial chest radiograph and a subsequent shoulder radiograph revealed a calcific mass (A). During the 9 years of observation, follow- up examinations showed no inter- val change in the mass or new symptoms.

A noncontrast CT scan showed a heavily calcified mass with a broad base of attachment to the medial aspect of the scapula (B, arrows). The cortex and medullary cavities of the mass were in continuity with the remainder of the scapula. The mass extended perpendicular to the plane of the scapula toward the ribs. No soft tissue component was appreciable on the CT scan (C). A 3-dimensional reformatted image depicted the cauliflower-shaped calcific mass, extending perpendicularly from the scapula toward the rib cage (D, viewed from behind the patient). Based on these findings, Joel M. Schwartz, MD, of Elmsford, NY, diagnosed a benign sessile osteochondroma of the scapula.

Osteochondromas can be either single--as in this patient--or multiple. Rarely, a patient may have widespread lesions and a family history of the condition (hereditary multiple exostoses). A solitary osteochondroma is the most common benign skeletal growth. It is usually detected in childhood, although it may be found later in life. The mass may be discovered when it becomes palpable or symptomatic as a result of compression of adjacent structures or when a fracture occurs. It may also be detected incidentally on radiographs.

Osteochondromas are found more frequently in men (male-to- female ratio, approximately 2:1). Because many lesions remain undetected, the true rate of occurrence is unknown.

Osteochondromas most commonly affect the femur. They vary in size (from 1 to 15 cm) and may be pedunculated or sessile. Pedunculated osteochondromas are more common and can affect the knee, hip, or ankle. Sessile osteochondromas are most frequently seen in the humerus and scapula. About 1% of solitary osteochondromas undergo malignant degeneration. Rapid enlargement and development of pain suggest malignant transformation.

Treatment is unnecessary unless symptoms develop or malignant degeneration occurs.

References:

FOR MORE INFORMATION:

• Stoller D, Tirman P, Bredella MA, et al. Diagnostic Imaging: Orthopaedics. Salt Lake City: Amirsys; 2004.
• Yochum TR, Rowe LJ. Essentials of Skeletal Radiology. Baltimore: Lippincott Williams & Wilkins; 1987:786-792.