Enchondroma
Enchondroma is a benign tumor of bone that represents a hamartomatous process.
Usually the lesions are asymptomatic and will present as an incidental
finding or pathologic fracture. Fifty
percent of these lesions will involve small
tubular bones of the hands and feet, where pathologic fractures are common. There is no age, race, or gender
predilection. The lesions tend to
involve the metaphyseal regions of
the proximal femur and humerus and distal femur. The hand is the exception in that it often involves the diaphysis.
Radiographically the lesions of the
hands and feet are distinct from the lesions of the long bones. Lesions of the long bones are central and lytic with sharp margins, variable amounts of calcific stippling and no cortical
involvement. On the contrary,
lesions of the hands show marked cortical
thinning and expansion with associated central calcific stippling (Figure
#9,10). Absence of calcific stippling
is not uncommon in active lesions. Histologically
the lesions are also distinct. In the metaphyseal lesions of long bones there are found small numbers
of cells within lacunae and no concerning features. Lesion of the hands and feet, however, show
worrisome histological features and hypercellularity.
|
Figure
#9
Enchondroma of the proximal phalanx. |
Figure # 10
Enchondroma of
the distal femur |
Multiple enchondromatosis, or Ollier’s disease, describes the
presence of multiple enchondromatous lesions throughout the metaphysis of
multiple bones. It typically involves
bones on a single side of the body
and is capable of causing shortening and bowing of the affected regions while
thinning the cortex dramatically. It is
not infrequently confused with polystotic fibrous dysplasia. The presence of mutiple enchondromas and
soft-tissue angiomas is known as Mafucci’s
syndrome.
The risk of malignancy with these
lesions is slight. There is less than
5% risk with an isolated lesion and solitary lesions of the hand are even
less. Conversion to cancer occurs thru
the process of dedifferentiation to
chondrosarcoma. For the
pathologist, this spectrum of disease is problematic and often a low-grade
chondrosarcoma is indistinguishable from an enchondroma. In most cases, onset of new pain concurs
with the dedifferentiation process.
Ollier’s disease has an elevated risk at 20-30% risk of conversion and Maffucci’s has a near 100% conversion risk,
making proper diagnosis and follow-up imperative. In addition, those with multiple enchondromatosis have an
increased risk of visceral malignancies such as GI malignancies and
astrocytomas.
Treatment of the incidental finding
of a lesion is watchful waiting. If the
lesion becomes symptomatic then curettage of the lesion with pathologic
examination is warranted. Pathologic
fractures of the fingers and toes are allowed to heal and then the lesions are
curetted and bone grafted.
