Clinical History
A 17 year-old woman applied with the complaints of swelling and pain in her left knee. She had been having a lump in the region for years; but pain had started later, as the lump grew bigger. She
also complained from cosmetic disturbance.
Imaging Findings
Our case is a 17 year-old young woman. She came to our hospital with pain in her left knee. There was also a swelling at the lateral aspect of her left knee joint. She gave a history of years for
this swelling. But pain had started recently, as the lesion grew bigger. The growth of the lesion had led to a bulky appearance at the site; and she was also complaining from cosmetic disturbance.
Her X-rays were obtained; and they showed an expansile bony mass at the fibular head. The mass was in continuity with the host bone. The transitional zone was sharp and clear-cut. General appearance
of the lesion gave a benign impression; in fact the pattern was typical for an osteochondroma or, exostosis. The patient was also examined by magnetic resonance imaging (MR), for a better and
detailed viewing. The T1-weighted images clearly outlined the lesion borders, which were sharp, and again, in full continuity with the fibular contours. There was slight enhancement of the lesion
after gadolinium administration. No malignant signs, such as aggressive destruction and massive contrast uptake, were encountered. The diagnosis of a solitary osteochondroma was made. The patient was
operated, mainly due to the clinical problems of pain and cosmetic disturbance. Pain was due to the impression effects of the mass on nerves and vessels nearby. The lesion was excised; and the
pathology result came as osteochondroma. She is now in very well condition, physically and psychologically.
Discussion
Solitary osteochondroma, or osteocartilaginous exostosis, is a hyperplastic/dysplastic bone disturbance originating from displaced or aberrant cartilage of the growth plate. There is a developmental
osseous anomaly resulting in exophytic outgrowth on surface of bone.Growth ends when nearest epiphseal plate fuses. Solitary osteochondroma is the most common benign growth of the skeleton; and it
constitutes 45% of all benign tumors and 12% of all bone tumors . It is most frequently seen between the first and third decades; and the male:female ratio is 1:1. But this ratio is reported as
1.8-2.1 in some different sources . The mass itself is usually painless, and present for many years. But there may be pain with impingement on nerves and blood vessels. Bursitis may form over cap.
Pain in the absence of fracture, nerve compression, or bursitis is considered malignant until proven otherwise. Osteochondroma is usually a benign lesion with self-limited growth. Malignant
transformation may ocuur in 1-2% of solitary lesions. Gd enhanced MR examination may help in the differentiation of a malignant outgrowth by depicting aggressive contrast uptake by the tumor tissue.
The radical method of therapy for the lesion is surgical resection. If the entire cartilage cap is removed, recurrence is unlikely (<5%).The common sites of the tumor are the long bone metaphyses
of the femur, humerus, proximal radius, tibia (50%about knee); scapula; rib; pelvis; and spine (1-5% commonly thoracic). But it may be encountered in any bone that develops by enchondral
calcification. There are mainly two types of the tumor: a) pedunculated form, b) broad-based form. The cartilage may ossify or calcify. As for the microscopic features, there is a cartilage cap
containing a basal surface with enchondral ossification. There may be a bursa at the periphery of some osteochondromas, attached to the perichondrium of the cap. The bursa wall is usually lined by
synovium. The best diagnostic clue is the presence of an exostosis with continuity of bone cortex and medullary marrow space to host bone. There is a cartilage-covered bony projection (exostosis) on
the external surface of the bone. The hyaline cartilage cap is usually calcified. In the pedunculated type, slender pedicle is directed away from the joint; and the lesion grows at right angles to
the long axis of the host bone. In the sessile type, there is a broad-based attachment to the cortex. In some osteochondromas, there may be undertubulation of long bones (Erlenmayer flask deformity).
Main signs of malignant deformation are the development of thick and bulky cartilaginous cap (thickness>1 cm), the presence of dispersed calcifications within cartilaginous cap, and the
development of a soft tissue mass. Parosteal osteosarcoma, periosteal chondroma, chondrosarcoma, juxtacortical myositis osssificans, and subungual exostosis are the main entities in the differential
diagnosis list.
Differential Diagnosis List
Solitary Osteochondroma (Exostosis) of The Fibular Head
Final Diagnosis
Solitary Osteochondroma (Exostosis) of The Fibular Head
