Malignant degeneration of an osteochondroma with unusual intra-bursal invasion

Abstract

Multiple hereditary osteochondromatosis is an uncommon autosomal dominant condition in which patients are predisposed to the development of chondrosarcoma. We report a case of a patient who developed a secondary low-grade chondrosarcoma in this setting. The tumor was associated with an unusual multinodular invasive growth pattern into a pre-existing bursa that was present overlying the osteochondroma.

Cervical Spine Osteochondroma: Rare Presentation of a Common Lesion

“…A change in cap thickness in an adult with a cap greater than 2.0 cm should prompt concern for malignancy. 13 In our case, the cartilaginous cap measured 8.0 mm. The radiographic appearance of a bursa overlying an osteochondroma may be mistaken for malignant transformation of the cartilaginous cap.…”

“…11 Some osteochondromas may develop an overlying friction bursa that may become symptomatic if inflamed. 13 Rare instances of synovial osteochondromatosis of the bursa have been reported. 13 Myelopathy 11,14 and radiculopathy, 9,11,14,15 which are rare complications, have been associated with paraplegia, 11 tetraplegia, 6 and sudden death from subtotal spinal cord transection, BrownSequard syndrome, and Friedrich's ataxia.…”

“…13 Rare instances of synovial osteochondromatosis of the bursa have been reported. 13 Myelopathy 11,14 and radiculopathy, 9,11,14,15 which are rare complications, have been associated with paraplegia, 11 tetraplegia, 6 and sudden death from subtotal spinal cord transection, BrownSequard syndrome, and Friedrich's ataxia. 9 Govender and Parbhoo 11 described a case of a solitary cervical osteochondroma compressing the C8 and T1 roots that presented with symptoms mimicking entrapment neuropathy of the ulnar nerve.…”

“…9 Malignant degeneration into chondrosarcoma (most common), osteosarcoma, and fibrosarcoma is possible with a reported incidence of approximately 1% in solitary osteochondroma and 5% to 25% in HME, although, the exact incidence of malignant degeneration is not known. 2,8,13 A change in size of an osteochondroma or new onset of symptoms warrants investigation, as it may herald malignant degeneration. Some osteochondromas may retain a cartilaginous cap after skeletal maturation, and patients with these tumors may be at risk for development of chondrosarcoma.…”

“…In that case, cross-sectional imaging, preferably MRI, should be performed followed by biopsy. 13 Both ultrasound and MRI can reliably distinguish between secondary bursitis and malignant transformation of an osteochondroma due to the fluid signal characteristics of the overlying bursa. 19 In addition, MRI contrast enhancement can differentiate between benign and malignant cartilaginous tumors.…”