Published Works: Cartilage
Forming Tumors Benign Cartilage Forming Tumors
Osteochondroma
Osteochondroma represents the most common benign bone tumor, and accounts for
approximately 35 percent of all benign bone neoplasms. It occurs most frequently
in the second decade, and most lesions are located in the distal femur, proximal
tibia, and proximal humerus. These lesions result from disordered enchondral
bone growth, probably from displaced epiphyseal cartilage. They arise from the
metaphyseal surface of bone, adjacent to the physis. They may be sessile or
pedunculated and often grow away from the nearby joint. These tumors may rarely
arise in bone that was previously irradiated during childhood.
Osteochondroma usually presents as a painless mass unless the tumor has fracutred,
which rarely occurs. The overlying structures may be compressed, and sometimes
a painful bursa develops over the tumor. Tumor growth is seen during childhood
and usually ceases after skeletal maturity.
The radiographic feature of an osteochondroma is the presence of a bony projection
arising from the metaphyseal surface of the cortex in which there is continuity
between the cortex and medullary bone of the lesion and that of the affected
bone.
Grossly, the lesion, either pedunculated or sessile, consists of a cartilage
cap with underlying trabecular bone. The cap is usually less than 1 cm thick.
A bursa often covers the lesion. Histologically, the cap consists of hyaline
cartilage covered by thin fibrous perichondrium. At the junction with the underlying
bone, the cartilage cap often resembles an epiphyseal growth plate with active
endochondral ossification. The chondrocytes are arranged in a columnar fashion
and have small, darkly stained nuclei that rarely may show cytologic atypia.
There is a risk of malignant transformation to chondrosarcoma which is less
than 1 percent in solitary lesions. The risk of transformation seems to be related
to the thickness of the cartilage cap. A thick bosselated cap, particularly
one over 2 cm, should be worked up for malignancy. CT scanning is useful for
the evaluation of the cartilage cap and the degree of mineralization.
Most osteochondromas are asymptomatic and therefore no treatment is necessary.
Annual examination and radiograhpy should be used to follow the lesions, with
CT scans to evaluate painful or enlarging lesions. Lesions about the elbow or
ankle may cause growth disturbance or interfere with motion at those joints.
In such cases excision may be indicated. Excision of an osteochondroma must
be done at the base of the stalk and include the cap and perichondrium. Care
should be taken to avoid disrupting the cap and perichondrium.
Osteochondromatosis (multiple hereditary exostosis) is an autosomal dominant
disorder in which the patients have multiple tumors involving several bones.
The disorder is often marked by a mild decrease in stature, leg length discrepancy,
and angular deformities of the knee, elbow, and ankle. The risk of malignant
transformation to chondrosarcoma is probably less than 5 percent.
Subungual Exostosis
Subungual exostosis is a bony projection arising from the subungual region of
the distal phalanx, usually from the great toe. The lesion is composed of trabecular
bone covered with fibrocartilage and hyaline cartilage. Subungual exostosis
is a reactive process probably related to trauma or infection, and is apparently
unrelated to osteochondroma.
Bizarre Parosteal Osteochondromatous Proliferation
of the Hands and Feet (BPOP)
Bizarre parosteal osteochondromatous proliferation of the hands and feet (BPOP)
is a benign lesion arising from the cortical surface of shorter tubular bones
and is composed of cartilage, bone, and fibrous tissue. It is different from
osteochondroma and is probably posttraumatic. It has also been described in
the long bones.
Enchondroma
Enchondroma is relatively common benign tumor of mature hyaline cartilage, originating
within the medullary cavities of long bones, possibly from remnants of the epiphyseal
plate. It accounts for approximately 10 percent of the benign bone tumors. Endochondromas
occur most commonly in the second, third, and fourth decades of life, but are
seen in all age groups. They are most typically found in the short tubular bones
of the hands and feet, but are frequently seen in the femur and humerus as well.
Most enchondromas are painless and are diagnosed incidentally on radiographs.
Pain should raise the question of a pathologic fracture or malignancy if the
lesion is in a long bone. Radiographically these tumors display the characteristic
punctate calcifications common to cartilage-forming tumors. The tumors are usually
well-defined cartilage-forming tumors. The tumors are usually well-defined with
clear demarcation between them and the surrounding normal bone. In the phalanges,
they tend to expand the bone and thin the cortex. The matrix may be focally
calcified. Enchondromas of long bones may sometimes be difficult to distinguish
radiographically from a bone infarct or low-grade chondrosarcoma.
Grossly the tumor is translucent and blue-gray in color. Histologically, it
is lobulated and usually hypocellular, with a typical cartilaginous matrix containing
normal-appearing chondrocytes located within lacunae. The cells have small uniform
nuclei lacking atypia. The matrix may be focally calcified. Enchondromas of
the hands and feet are often more cellular than those of the long bones.
Asymptomatic lesions can simply be observed and followed longitudinally. Symptomatic
lesions should be biopsied to confirm the benignity of the lesion, and at the
same time should be curretted and bone grafted.
Ollier’s disease is the eponym for multiple enchondromatosis. It is usually
unilateral and has an incidence of malignant transformation to chondrosarcoma
that is reported to be 10 to 30 percent. Maffucci’s syndrome is characterized
by multiple enchondromas with soft tissue angiomas. The incidence of malignant
transformation in this condition is probably higher than in enchondromatosis.
Periosteal Chondroma
This uncommon lesion arises from the outer cortex of long and short tubular
bones, beneath the periosteum. It is most commonly seen in patients in their
second to third decades of life. The proximal humerus and proximal and distal
femur and phalanges are common locations. The tumor may present as a palpable
mass with local tenderness.
Radiographically, these tumors are well-defined, small metaphyseal surface lesions
with erosion of the outer cortex and reactive periosteal bone formation. One-third
are calcified. Histologically, they exhibit lobulated hyaline cartilage, but
they are usually more cellular with greater plemorphism and cell binucleation
than enchondromas.
The recommended treatment is en bloc resection.
Chondroblastoma
Fifty to 65 percent of these benign tumors occur in the second decade of life
and are most commonly found in the proximal humerus, distal femur, or proximal
tibia. The lesion is characteristically centered in the epiphysis, but it may
be in an apophysis or the triradiate cartilage of the pelvis.
Pain localized to the region of the tumor is the most common presenting symptom.
Physical findings are often subtle, and may include tenderness, a limp or pain
on motion of the affected joint. Radiographically, the lesion is radiolucent,
with well-defined sclerotic borders that clearly define its limits from the
surrounding epiphyseal trabecular bone. The amount of mineralization within
the bone is variable, occurring in at least 25 percent of cases. The tumor may
cross an open physis and expand the surrounding bone.
Grossly, the lesional tissue is grayish-pink in color, measuring between 1 to
7 cm (usually less than 3 cm). Calcific foci may be apparent in the tissue.
Since a secondary aneurysmal bone cyst component may be present, hemorrhagic
tissue may be prominent.
Microscopically, the predominant cells are round to polyhedral with well-defined
cell borders containing often-indented nuclei. Varying degrees of chondroid
differentiation are seen. Matrix calcification may take on a characteristic
"chicken wire" appearance around the individual cells. Multinucleated
giant cells may be present—scattered and sometimes in large numbers. Cystic
spaces resembling aneurysmal bone cyst are seen in approximately 20 percent
of the cases. Immunohistochemical studies have shown that the chondroblastoma
cells react positively to S-100 protein. Because of its epiphyseal location
and the presence of giant cells, chondroblastoma may be confused with giant
cell tumor.
Most chondroblastomas can be successfully treated with curettage and bone grafting
with an approximate 90 percent cure rate. Rarely, chondroblastomas can be locally
aggressive or can metastasize to the lungs. There are rare documented cases
of malignant transformation.
Chondromyxoid
Fibroma
This rare benign cartilage tumor occurs most commonly in the second and third
decades, with two-thirds occurring in long bones and approximately 25 percent
localized to the proximal tibia. While some of these are picked up as incidental
findings, the majority are painful. In some cases, local swelling and a palpable
mass are noted. Physical exam is usually unremarkable, other than occasional
tenderness.
Radiographically, the lesions have an eccentric metaphyseal location. They are
lytic lesions, and are lobular and sharply demarcated from the normal surrounding
bone by a scalloped slightly sclerotic rim. The overlying cortex is thinned
and often expanded. Matrix calcification is unusual. Tumors arising from small
tubular bones such as the ulna, metatarsal, or metacarpal are usually centrally
located and produce symmetric expansion of the bone.
Grossly, the tumor may take on a well-circumscribed, lobulated appearance, with
translucent bluish-gray color that resembles cartilage. Microscopically, the
tumor is poorly lobulated and contains spindled and stellate cells with an abundant
myxoid matrix. Peripheral hypercellularity of the lobules is common; multinucleated
giant cells are often found in the fibrous tissue between the lobules, and round
cells resembling chondroblasts may be seen in these areas. Well-developed hyaline
cartilage is unusual in these tumors. Cellular atypism with hyperchromatism
may be found, but mitoses are rare.
Treatment usually involves intralesional curettage and bone grafting. Recurrence
rate is approximately 10 to 15 percent. In some cases, the tumors are locally
aggressive and extend into soft tissues, requiring wider local resection. Malignant
transformation to chondrosarcomas is exceptional.
Malignant
Cartilage Forming Tumors
Chondrosarcoma
(Conventional, Central)
Chondrosarcoma is a common malignant neoplasm of cartilage cells that is seen
predominantly in adults between 40 and 70 years of age, rarely in patients younger
than 20. If multiple myeloma is excluded, chondrosarcoma is the second most
common primary malignant tumor of bone after osteosarcoma. Most lesions occur
in the pelvis, followed by the femur and proximal humerus. The most common presenting
symptom is localized pain of relatively long duration, anywhere from several
months to more than 10 years. Physical findings are often subtle and may include
pain on examination of the adjacent joint, mind muscular atrophy, tenderness,
a palpable mass, and an antalgic gait.
Radiographic features are characteristic, often diagnostic. Central chondrosarcomas
of long bones occur primarily in the metaphysis or diaphysis. There is cortical
thickening, endosteal scalloping, and often fusiform expansion of the bone.
Matrix calcification in a stippled or ring-like pattern is frequently seen,
particularly in low-grade malignant tumors. Soft tissue extension may be seen
with larger tumors and is associated with cortical destruction. Involvement
of the medullary cavity by tumor may be extensive. Pain, in association with
endosteal scalloping and cortical thickening, is important diagnostic clues
in distinguishing low grade chondrosarcoma from the benign enchondroma.
Grossly, chondrosarcomas tend to be lobulated, with a blue-gray translucent
cartilaginous appearance, interspersed with white areas of calcification. Areas
of myxoid degeneration, necrosis, and liquefaction help distinguish this malignant
tumor from the benign cartilage-forming lesions. Histologically, the tumors
vary greatly in their degree of cellularity and matrix composition. In well-differentiated
chondrosarcomas (grade 1), the tissue is lobulated and contains chondrocytes
lying within lacunae separated by abundant hyaline matrix. The cells show mild
to moderate nuclear pleomorphism and are often binucleated. The tumor is moderately
cellular and no mitosis are seen. Although some grade 1 chondrosarcomas can
be indistinguishable histologically from enchondroma, the presence of tumor
infiltration of the marrow spaces and the aggressive radiographic appearance
is diagnostic of malignancy. In grade 2 chondrosarcomas, there is an increase
in cellularity and nuclear atypia as well as the presence of multinucleated
tumor cells, and occasional mitoses. Myxoid changes are common. The grade 3
chondrosarcomas show highly malignant cells and less evidence of cartilaginous
differentiation.
Secondary chondrosarcomas, as opposed to primary central chondrosarcomas, arise
at the site of preexistent benign cartilage tumors such as enchondromatosis,
osteochondromatosis, and solitary osteochondroma, and rarely in solitary enchondroma.
They are usually well-differentiated (grade 1).
Treatment of this malignancy is predominantly surgical, consisting of wide surgical
resection with adequate margins. Amputation may be necessary, but reconstruction
can be considered depending on the location. These tumors are not considered
responsive to routine chemotherapy or irradiation. The most important prognostic
factors appear to be the size of the tumor, anatomic location, and the histologic
grade. The overall 5-year survival rate is approximately 50 to 60 percent.
Dedifferentiated
Chondrosarcoma
This represents the most malignant cartilage tumor; dedifferentiation complicates
approximately 10 percent of all chondrosarcomas. It has a peak incidence in
the fifth to seventh decades of life, with a similar site predilection as the
conventional chondrosarcomas. Pain is typical, often varying with the rate of
tumor growth. The presence of an intraosseous tumor that radiographically resembles
enchondroma or chondrosarcoma, but showing cortical destruction and soft tissue
invasion without mineralization, strongly dedifferentiated chondrosarcoma.
Histologically, the tumor consists of a cartilaginous tumor of low-grade malignancy
and a noncartilaginous high-grade malignant component. There is sharp transition
between the two tissue elements. The low-grade cartilage component has features
similar to ordinary chondrosarcoma (usually grade 1); the high-grade component
may be malignant fibrous histiocytoma, fibrosarcoma, or osteosarcoma. This latter
component is the most aggressive of the tumor and extends into the soft tissue.
Long-term survival is less than 10 percent. Metastatic sites demonstrate the
high-grade noncartilaginous component. Amputation is usually necessary unless
wide margins can be achieved. Multiagent adjuvant chemotherapy is important
for addressing the spindle cell component.
Mesenchymal Chondrosarcoma
This rare tumor has a peak incidence in the third decade of life, but is spread
over a wide age range. Approximately one-third of the patients have had pain
for more than 1 year prior to diagnosis. One-third of cases occur in the soft
tissues; osseous predilection is in the pelvis, ribs, proximal femur, and jaw.
There are no characteristic radiographic features that help to differentiate
this tumor from ordinary chondrosarcoma. In the bone, the lesion is lytic and
stippled with calcifications, cortical destruction, and soft tissue extension.
Histologically, it consists of a bimorphic pattern with well-differentiated
chondrosarcoma intimately associated with hypercellular noncartilaginous tumor
consisting of round, oval, or spindle cells. This latter component has a conspicuous
vascular proliferation with a hemangiopericytomatous pattern of growth. The
histologic appearance of the areas containing round cells is reminiscent of
Ewing’s sarcoma. Areas of cartilage may be quite small, and reactive osteoid
may be present. Mitoses are sparse.
Treatment is surgical, requiring surgical resection with wide margins. Adjuvant
radiation and chemotherapy offer no proven benefit. Long-term prognosis is poor.
Clear Cell Chondrosarcoma
This rare, low-grade malignant neoplasm afflicts patients from the second to
ninth decades, with a peak incidence in the third and fourth decades. Patients,
usually male, often have pain and other subtle symptoms for several years prior
to diagnosis. Approximately 50 percent of cases affect the femoral head; the
proximal humeral epiphysis, the distal femur, and proximal tibia re the next
most frequently involved sites.
Radiographically, in its early stages, the tumor may look benign, with sharp
margins; focal calcification may be present. Larger, more advanced lesions are
poorly circumscribed, with marked cortical destruction.
Grossly a bluish-gray matrix may be difficult to see; hemorrhagic cystic spaces
may be present. Histologically, the tumor cells have abundant clear cytoplasm,
bland nuclear features, and the chondroid matrix is sparse and distributed between
the clear cells and is focally calcified. Scattered bone trabeculae, as well
as multinucleated giant cells, are frequent components of this tumor. Because
of its epiphyseal location, clear cell chondrosarcoma should be distinguished
from chondroblastoma, both radiologically and histologically.
Wide surgical resection without adjuvant therapy is the recommended treatment.
