There are many types of soft tissue masses or tumors that an individual may suffer from as well as many different types of bone tumors, both benign and malignant. These tumors have varying characteristics as well as age of onset. One can find many of these tumors incidentally via X-ray evaluation.
One bone tumor in particular is an osteochondroma, a bony/cartilage tumor with a bone-like stalk and a cap of cartilage.1,2,3 There are two types: pedunculated and sessile.3 Typically, osteochondromas occur in the metaphyseal region of the bone, rarely the diaphysis. One may confuse an osteochondroma with a subungual exostosis. Subungual exostoses commonly occur in 20- to 40-year-olds. Another major difference is in the type of cartilage on the cap: fibrocartilage (subungual exostosis) or hyaline cartilage (osteochondromas). These differences are only visible under histologic evaluation.4
Of the benign bone tumors, osteochondromas are by far the most common type, representing about 50 percent of all benign bone tumors.1-5 Of all primary bone tumors, osteochondromas represent 10 to 20 percent.3 It is also the most common bone tumor in the foot. Osteochondromas are more commonly solitary lesions (90 percent of reported cases) but it is possible to have multiple lesions.3,4
What causes it? The true etiology of osteochondroma is not fully known but is theoretically due to an aberrant growth plate. Since the tumor arises from the growth plate, it will continue to enlarge throughout the growth phase and growth ceases when the growth plates are fully fused.1-3 The growth of this tumor is slow so patients will not have a tumor the size of a football forming in the foot or leg.
Who gets it? Osteochondromas are more common in individuals under the age of 20 and more common in males than females.1,3
Are there specific bones involved? Yes but other bones are not immune. Having said that, the distal end of the femur is the more common location. Other bones in which the tumor more commonly occurs are the tibia, fibula, humerus, proximal femur and scapula. Osteochondromas rarely occur in the bones of the fingers or toes.1-3 If there is digital involvement, it is typically in a subungual location.4
Are there symptoms? Typically, there are no symptoms of pain. As I mentioned previously, these tend to be incidental findings following X-rays clinicians take for other reasons. If symptoms do occur, they may be from impingement of a neurovascular structure, irritation of shoe gear, bursitis (because a bursa usually overlies the cartilage cap), or fracture of the tumor.1-3
What diagnostic tools are effective? Plain radiography is useful but will not reveal the extent of the cartilage cap. Magnetic resonance imaging (MRI) is a better tool to help identify the full lesion from the underlying normal bone. A bone scan can be useful in determining how active the lesion is. In other words, if there is increased uptake of the tracers, then the tumor is actively growing and this may be suggestive of a potential malignant change. On the other hand, if there is very little to no tracer uptake, then one can rule out the chance of malignant transformation.1,3
How do you treat osteochondromas? If the lesion is not painful, then one typically leaves this tumor alone. Once the tumor becomes painful, then surgical excision is the course of action.1-3
Can osteochondromas become malignant? Yes but it is extremely rare. If pain or growth persists beyond the cessation of growth (skeletal maturity), then the risk of a malignant change to chondrosarcoma is suggestive.3 Biopsy of the lesion is warranted to rule out this progression.3 Of note, the sessile form of this tumor is more likely to progress to a malignant chondrosarcoma than the pedunculated form.3 The risk of malignant transformation is about 1 percent with solitary lesions and 5 to 25 percent for those with multiple lesions.3 Researchers have linked a cartilage cap of ≥1 cm to chondrosarcomatous change.5
1. Christman R. Foot and Ankle Radiology. Elsevier Health Sciences, Philadelphia, 2002.
2. Coughlin M, Mann R, Saltzman C. Surgery of the Foot and Ankle, eighth edition. Mosby Elsevier, Philadelphia, 2007.
3. Banks A, et al. McGlamry’s Comprehensive Textbook of Foot and Ankle Surgery, third edition. Lippincott, Williams and Wilkins, Philadelphia, 2001.
4. Lee S, Jung MS, Lee YH, et al. Two distinctive subungual pathologies: subungual exostosis and subungual osteochondroma. Foot Ankle Int. 2007; 28(5):595-601.
5. Jackson K, Gurbani B, Otsuka NY. Osteochondromas of the talus presenting as intraarticular loose bodies: report of two cases. Foot Ankle Int. 2004; 25(9):630-1.