Enchondroma is a solitary, benign, intramedullary cartilage tumor that
is usually found in the short tubular bones of the hands and feet. The
peak incidence is in the third decade and is equal between men and women.
It is the most common primary tumor in the hand and is normally found
in the diaphysis. The mature hyaline cartilage located centrally within
short tubular bones usually presents clinically as a fracture due to an
enlarging lesion. Enchondromas are also found incidentally in long bones
and undergo malignant transformation in less than 1% of cases.
Multiple enchondromatosis is a non-heritable condition also known as Ollier's
disease. Multiple enchondromas and hemangiomas of soft tissue are otherwise
known as Maffucci's Syndrome. In both conditions, males are affected more
than women and the disease process often only affects one side of the
body. In both diseases, there is a 30% risk of malignant transformation
of the enchondromas. Enchondromas are difficult to differentiate
from low grade chondrosarcoma by radiology. Lesions located near the shoulder
or the pelvis may have a higher risk of sarcomatous degeneration (Krikun).
Chondrosarcoma is much more common in older patients, so large enchondromas
in older individuals demand a careful work-up.
Enchondromas are usually long and oval and have well-defined margins.
In larger lesions, the lucent defect has endosteal scalloping and the
cortex is expanded and thinned. Calcifications throughout the lesion can
range from punctate to rings. CT is useful for detecting matrix mineralization
and cortex integrity. MRI is helpful for describing the non-mineralized
portion of the lesion and visualizing any aggressive or destructive features.
Radiographic and imaging features of enchondroma that are considered worrisome
due to the potential for malignancy include large size, a large unmineralized
component, significant thinning of the adjacent cortex, and bone scan
activity greater than that of the anterior superior iliac spine. Features
of enchondroma that are very strongly associated with malignant transformation
are progressive destruction of the chondroid matrix by an expanding, non-mineralized
component, an enlarging lesion associated with pain, or an expansile soft
On gross examination, an enchondroma consists of bluish-gray lobules of
fine translucent tissue. The degree of calcification of the lesion determines
if the consistency is gritty.Under the microscope, a thin layer of lamellar
bone surrounding the cartilage nodules is a positive sign that the lesion
is benign. At low power, there are lobules of different sizes. Blood vessels
are surrounded by osteoid. Enchondromas have chondrocytes without atypia
inside hyaline cartilage. The nuclei are small, round and pyknotic. The
cellularity varies between lesions and within the same lesion.
Each potential enchondroma needs to be evaluated for cellularity, nuclear
atypia, double nucleated chondrocytes and mitotic activity in a viable
area without calcifications to distinguish it from low-grade chondrosarcoma.
Small peripheral lesions are more likely to be benign than large axial
lesions. The pathologic diagnosis is so difficult it always needs to be
made in conjunction with the radiologist and the surgeon.
A solitary painless enchondroma may be observed. Painful or worrisome
lesions should be treated with biopsy followed by intralesional resection.
Large defects can be filled with bone graft. All specimens must be analyzed
carefully for malignancy.
Gitelis, S. et al, Benign Bone Tumors, Instructional Course Lectures,
45:p. 426-46, 1991.
Giudici, A. et al, Cartilaginous Bone Tumors, Radiologic Clinics of North
Amenca, 31(2):p. 237-259, March 1993.
Bullough, Peter. Orthopaedic Pathology (third edition), Times Mirror International
Publishers Limited, London, 1997.
Huvos, Andrew, Bone Tumors: Diagnosis, Treatment and Prognosis, W.B. Saunders,
Krikun M. Imaging
of Bone Tumors Philadelphia, W.B Saunders, 1993