Ewing's sarcoma of the thumb
A technetium bone scan revealed very high tracer uptake in the
affected bone but no other abnormal foci in the rest of the
skeleton (not shown). A chest radiograph showed no metastatic
lesions (not shown). All laboratory data were within normal limits.
Disarticulation through the metacarpophalangeal joint of the thumb
was successfully performed, followed by chemotherapy.
X-rays of the right hand showed a purely lytic lesion of the distal
phalanx without periosteal reaction, which was accompanied by a
huge soft tissue tumor (Figure 1).
Considering the age of the patient and the clinical findings,
primitive neuroectodermal tumor (PNET)/ Ewing's sarcoma (ES) of the
thumb was the most probable radiologic diagnosis.
An incisional biopsy was performed. Under the light microscope,
the neoplasm was seen to be composed of sheets of tumor cells with
round-to-oval nuclei. The cytoplasm was scant, and the cell margins
were ill- defined. Periodic acid-Schiff (PAS) staining revealed
prominent cytoplasmic glycogen (Figure 2). Immunohistochemically,
the tumor cells expressed vimentin and MIC2, while desmin,
myoglobin, keratin, and S100 were negative.
Ewing's sarcoma, a highly malignant primary bone tumor, was first
described by James Ewing in 1921. The tumor is derived from red
bone marrow. Most frequently, it is observed in children and young
adults from 5 to 25 years of age. Ewing's sarcoma accounts for
approximately 5% of biopsy-analyzed bone tumors in patients of all
ages. It is the second most common malignant bone tumor in young
patients. Males are affected more frequently than females, with a
ratio of approximately 1.5/1.1,2
An association exists between ES and PNET. The majority of both
of these tumors (90%) share the cytogenetic translocation t(11;22)
(q24;q12) or (21;22) (q22;q12), with occasional variations, and a
characteristic immunohistochemical staining profile. Both of these
tumors are believed to show neuroectodermal differentiation, albeit
in different degrees. Ewing's sarcoma tends to be poorly
differentiated, whereas PNET most often shows definite
neuroectodermal differentiation. Although once viewed as distinct
entities, ES of bone, extraosseus ES, Askin's tumor, and PNET are
now considered together as members of the Ewing's family of
tumors.3,4As such, they are increasingly grouped
together for both treatment and prognostic factor analysis.
The histogenesis of ES remains controversial, and current wisdom
as to the cellular origin is divided between mesenchymal cells,
possibly osteoprogenitor cells of the bone marrow, or
neuroectodermal cells.3,4 Most frequently, the tumor is
diagnosed as a monostotic lesion in the metaphysis or diaphysis of
the long bones of the extremities. The tumor also may occur,
although less frequently, in the pelvic area, ribs, and
scapulae.1,2 Ewing's sarcoma rarely affects the hand.
Kissane and coworkers1 indicated the incidence of ES
involving the hands to be 0.3% of all cases of ES, and
Dahlin2 reported the figure as 1%.
In ES of the hands, the middle and index fingers are the most
commonly involved. The metacarpals are more commonly affected than
the phalanges.5 As with tumors in other locations, pain
and swelling are the 2 most common presenting complaints, and they
may tend to be progressive. Low-grade fever is common, and these
patients may have elevated erythrocyte sedimentation rate and
leukocytosis. Few patients have a history of local trauma, and the
symptoms may vary in duration from a few weeks to many
The classic radiographic features of ES-namely, lytic permeative
destruction, aggressive periosteal reaction, cortical violation,
and a soft tissue mass-are also typically present in lesions of the
hands. A purely lytic lesion is less common in the small bones of
the hands than in other bones. Within the short tubular bones of
the hands, most ES tumors are centered in the metadiaphyseal
region, similar to the trend in long bones.5-
The definitive diagnosis of ES requires a biopsy specimen.
Morphologically, the neoplasm is characterized by monotonous sheets
of hyperchromatic cells with round-to-oval nuclei, high
nuclear-to-cytoplasmic ratios, and scant cytoplasm. Cytoplasmic
glycogen can often be detected by PAS stain or electron microscopy.
Afiligree pattern of infiltration in soft tissue is associated with
an adverse prognosis. The immunohistochemical profile usually
exhibits immunopositivity to vimentin and the MIC2 gene product.
The MIC2 gene product is a cell surface glycoprotein found on ES
cells and is very useful in the differential diagnosis. Antibodies
to the MIC2 gene product include 12E7, O13, and HBA71 (CD99).
Specimens of ES may mark for S100 protein and neuron-specific
enolase.9 The immunohistochemical features of the
presented cases correspond well to those of conventional ES.
The treatment of ES continues to be controversial. Recent
reports have emphasized the role of surgical extirpation and
adjunctive chemotherapy, especially in the absence of metastatic
disease. In the hand bones, resection removes the tumor with
radical margins and preserves the function, and the results are
The prognosis of ES involving the digits seems to be even better
than that of ES that involves more usual sites. This is probably
because the phalanges are the most peripheral bone; tumors can be
excised with a wide margin. Consequently, ES of the digit may lead
to an excellent prog-nosis.7
Ewing's sarcoma is a highly malignant, small, round-cell
neoplasm that usually arises in the medullary cavity of bone. The
most common sites for the primary lesion are the long bones,
pelvis, and ribs. The case described here is unusual because of its
location and the volume of the extraskeletal mass.
- Kissane JM, Askin FB, Foulkes M, et al. Ewing's sarcoma of
bone: Clinicopathologic aspects of 303 cases from the intergroup
Ewing's sarcoma study. Hum Pathol. 1983;14:773-779.
- Dahlin DC, Unni KK.Bone Tumors:General Aspects and Data on
8,542 cases. 4th ed. Springfield, IL: Charles C. Thomas Publishers,
- Delattre O, Zucman J, Melot T, et al. The Ewing's family of
tumors- A subgroup of small-round-cell tumors defined by specific
chimeric transcripts. N Engl J Med.1994; 331:294-299.
- Baldini EH, Demetri GD, Fletcher CD, et al. Adults with Ewing's
sarcoma/primitive neuroectodermal tumor: Adverse effect of older
age and primary extraosseous disease on outcome. Ann Surg. 1999;
- Baraga JJ, Amrami KK, Swee RG, et al. Radiographic features of
Ewing's sarcoma of the bones of the hands and feet. Skeletal
- Mohan V, Gupta RP. Ewing's sarcoma of the small bones of hands
and feet. Ind J Radiol Imag. 2002;12:403-405.
- Yamaguchi T, Tamai K , Saotome K, et al. Ewing's sarcoma of the
thumb. Skeletal Radiol. 1997;26:725-728.
- Zelazny A, Reinus WR, Wilson AJ. Quantitative analysis of the
plain radiographic appearance of Ewing's sarcoma of bone. Invest
Radiol. 1997; 32:59-65.
- Llombart-Bosch A, Contesso G, Peydro-Olaya A. Histology,
immunohistochemistry, and electron microscopy of small round cell
tumors of bone. Semin Diagn Pathol. 1996;13:153-170.