Radiographic evidence of regression of a solitary osteochondroma: a report of 4 cases and a literature review.

Solitary osteochondromas are considered to be the most common benign bone tumor. Slow progressive osteochondroma growth is the rule in skeletally immature patients, at times prompting surgical excision. Significant growth of a lesion beyond skeletal maturity is commonly considered to be a harbinger of malignant transformation. Although spontaneous regressions of these lesions are sporadically reported in the literature, most practitioners consider spontaneous regression of an existing solitary osteochondroma to be extremely unlikely. The purpose of this case report was to offer a collection of 4 new well-documented cases of radiographic evidence of regression of solitary osteochondromas in skeletally immature patients. A review of the literature is also presented. Twenty cases have been reported in the literature on spontaneously regressing solitary osteochondromas, with approximately 50% of the cases in radiology journals, and never more than 2 cases having been reported at one time, until now. Asymptomatic solitary osteochondromas may not be diagnosed or lack long-term follow-up, thereby contributing to the true unknown incidence of resolving osteochondromas. Although there are now only 24 documented cases in the literature of solitary osteochondromas that have spontaneously regressed, the rarity of this lesion is completely uncertain, as most go undiagnosed. The review of the suggested mechanisms by which solitary osteochondromas spontaneously regress is presented. Surgical excision is not without risk, with reported complication rates as high as 12.5%. These cases demonstrate that osteochondromas can actually resolve, and that conservative treatment by observation and yearly radiographs is an option for these lesions, especially in an asymptomatic pediatric patient. From the review of the literature most lesions were resolving before skeletal maturity and within 3 years of identification. Lesions that are symptomatic can be treated according to the patient's symptoms. This information should prove to be useful for patients and treating physicians when discussing treatment options for solitary osteochondromas, and reduce unnecessary surgery for these lesions.