Diagnostic imaging studies from three different patients with
the same condition are shown, including T1-weighted transaxial and
T2-weighted coronal images from an MR examination of a foot lesion.
What is the most likely diagnosis?
This relatively common malignant tumor of bone has a varied
histological pattern. The tumor cells are arranged in broad sheets.
Some cells have a larger, lightly stained, finely granular nucleus
with pale, ill-defined cytoplasm, whereas others possess small,
darker staining nuclear chromatin feltwork with a rim of moderately
well delineated cytoplasm; cells may be located about vessels in a
perithelial arrangement. A large-cell variety also has been
described. The origin of Ewing's sarcoma is unknown; it may be
derived from mesenchymal cells of the bone marrow of immature
reticulum cells or from vascular or myelogenic elements.
Ewing's sarcoma usually is identified in patients in their
first, second, or third decades of life, and the ratio of affected
men to affected women is approximately 3:2. Symptoms of localized
pain and swelling may be combined with fever, weight loss, anemia,
and leukocytosis, simulating the clinical findings of an infection.
Any skeletal site can be involved, although the most frequent sites
of involvement are the long tubular bones (the femur, tibia,1
humerus, and fibula), the pelvic girdle, the vertebrae, the ribs,
and the scapula. Ewing's tumor found in the craniofacial region or
the small bones of the hand and foot2 is less typical. It is found
more frequently in patients who are over the age of 18 years.
In the tubular bones, Ewing's sarcoma predilects the diaphyseal
or diametaphyseal region. It is characterized by a long permeative
osteolytic lesion with poorly defined margins, cortical disruption,
and a periosteal reaction.3 The periostitis frequently is described
as being of the "onion peel" or "hair-on-end" type. Pathologic
fractures are identified in 5 to 10% of cases. Saucerization and
excavation of the cortex also are noted in some tumors and this
feature may be the most prominent radio-graphic finding. In some of
these cases, an eccentric or cortical location of the tumor may be
apparent on pathological examination. In the flat bones, permeative
destruction also is typical. In this location, the amount of new
bone formation may be striking. In the vertebral column, the
sacrum, lumbar spine, thoracic spice, and cervical spine may be
involved, in order of descending frequency. Osteolysis and
vertebral collapse predominate. Occasionally, uniform sclerosis of
a vertebral body may be seen. Tumor extension into the posterior
elements also can be evident. Paravertebral masses, loss of height
of intervertebral disc spaces, and spread to contiguous vertebral
bodies are additional radio-graphic features of spinal
Skeletal and extraskeletal metastasis due to Ewing's sarcoma is
frequent. Osseous changes in these cases may simulate those in
leukemias, lymphomas, or metastatic neuroblastomas.
1. Resnick D: Bone and Joint Imaging. 2nd edition. Philadelphia,
WB Saunders, 1996.
This series of diagnostic challenges is prepared by David J.
Professor, Department of Radiology, University of California
School of Medicine,
San Diego, CA.