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U N I T 1 2
Musculoskeletal Function
Osteosarcoma
Osteosarcoma is an aggressive and highly malignant
bone tumor.
18,19,44–46
It is the most common malignant
bone tumor, representing one fifth of all primary bone
tumors.
19
The tumor has a bimodal distribution, with
75% occurring in persons younger than 20 years of
age.
19
A second peak occurs in the elderly with pre-
disposing factors such as Paget disease, bone infarcts,
or prior irradiation. Overall, men are more commonly
affected than women.
The cause of osteosarcoma is unknown. The correla-
tion of age and location of most of the tumors with the
period of maximum growth suggests some relation to
increased osteoblastic activity. In younger persons, the
primary tumor most often is located at the anatomic
sites associated with maximum growth velocity—the
distal femur, proximal tibia, and proximal humerus.
Bone tumors in the elderly are more common in the
humerus, pelvis, and proximal femur. There are known
genetic factors associated with osteosarcoma. Mutations
in two genes are reported to increase susceptibility: the
retinoblastoma gene (
RB
), a critical cell cycle genera-
tor; and the p53 gene, which regulates deoxyribonucleic
acid (DNA) repair and certain aspects of cellular metab-
olism
19
(see Chapter 7).
Osteosarcomas are aggressive tumors that grow rap-
idly in a circular, ball-like mass in the bone tissue. They
often are eccentrically placed in the bone and move
from the metaphysis of the bone out into the periosteal
surface, with subsequent spread to adjacent soft tissues
(Fig. 43-11). These tumors spread through the blood-
stream; most often, the tumor cells exit the primary
tumor through the venous end of the capillary, and early
metastasis to the lung is common. Lung metastases,
even if massive, usually are relatively asymptomatic.
The prognosis for a person with osteosarcoma depends
on the aggressiveness of the disease, presence or absence
of pathologic fractures, size of the tumor, and rapidity
of tumor growth.
The primary clinical feature of osteosarcoma is deep,
localized pain with nighttime awakening and swelling
in the affected bone. Because the pain is often of sud-
den onset, patients and their families often associate the
symptoms with recent trauma. The skin overlying the
tumor may be warm, shiny, and stretched, with promi-
nent superficial veins. The range of motion of the adja-
cent joint may be restricted.
The treatment of osteosarcoma is surgery in combi-
nation with multiagent chemotherapy, both before and
after surgery.
45,46
In the past, treatment usually entailed
amputation above the level of the tumor. Limb salvage
surgical procedures, using a metal prosthesis or cadaver
allograft, are now a standard alternative. In younger
children who undergo arthroplasty, an expandable
internal prosthesis is used to allow for bone growth.
Amputation is another surgical option. It involves either
the removal of expendable bones such as the fibula,
toes, or ulna, or the complete removal of the tumor and
the affected limb.
Chondrosarcoma
Chondrosarcoma consists of malignant tumors of cartilag-
inous lineage and is commonly subclassified according to
site of origin as central (intramedullary) or peripheral (jux-
tacortical and surface).
18,19
Chondrosarcomas can arise as
a primary tumor from preexisting benign cartilage tumors
such as osteochondroma or chondroblastoma.
47
They
commonly arise in the central portions of the skeleton,
including the pelvis, shoulder, and ribs (see Fig. 43-10).
Chondrosarcomas develop about half as frequently
as osteosarcomas. They occur primarily in middle or
later life; however, there are chondromas that occur in
younger persons. Chondrosarcomas are slow growing
and metastasize late, and often are painless. They can
remain hidden in an area such as the pelvis for a long
period of time. This type of tumor, like many primary
malignancies, tends to destroy bone and extend into the
soft tissues beyond the confines of the bone of origin.
Early diagnosis is important because chondrosar-
comas respond well to early radical surgical excision.
It usually is resistant to radiation therapy and avail-
able chemotherapeutic agents. Not infrequently, these
tumors transform into a highly malignant tumor, mesen-
chymal chondrosarcoma, which requires a more aggres-
sive treatment, including combination chemotherapy.
Ewing Sarcoma
Ewing sarcoma is a member of a family of tumors that
includes primitive neuroectodermal tumor (PNET).
Both tumors are characterized by densely packed, regu-
larly shaped, small cells with round or oval nuclei; and
both share a specific reciprocal translocation of chromo-
somes 11 and 31, or variants thereof.
19,42,48,49
FIGURE 43-11.
Osteosarcoma.The distal femur contains a
dense osteoblastic malignant tumor that extends through the
center in the soft tissue and epiphysis. (From Garcia RA, Klein
MJ, Schiller AL. Bones and joints. In: Rubin R, Strayer DS, eds.
Rubin’s Pathology: Clinicopathologic Foundations of Medicine.
6th ed. Philadelphia, PA: Wolters Kluwer Health | Lippincott
Williams &Wilkins; 2012:1244.)
