Athirty-eight-year-old, left-hand-dominant woman presented with a ten-year
history of ulnar pain in the left wrist. The medical history, including that
for gynecological disorders, was negative. Initially, the pain had been mild,
but four years before the patient presented at our institution, the symptoms
began to worsen. The patient took nonsteroidal anti-inflammatory medication
for approximately three months, with transient relief of symptoms. However,
two years later, the pain again worsened and began to limit the range of
motion of the left wrist and forearm.
Physical examination revealed moderate, diffuse swelling along the ulnar
dorsal aspect of the left wrist. Palpation of the distal aspect of the ulna
caused extreme pain that was centered mostly about the ulnar styloid and the
region of the sixth dorsal compartment. No mass was discernable, but the
distal aspect of the ulna appeared mildly prominent. Radiographs of the left
wrist (Fig. 1) demonstrated an
enlarged ulnar styloid but no other skeletal abnormality.
The patient was diagnosed with extensor carpi ulnaris tenosynovitis and was
treated with an injection of corticosteroid medication into the sixth extensor
compartment. She was given a wrist immobilizer, and a course of nonsteroidal
anti-inflammatory medication was prescribed. Three years later, the patient
presented with wrist pain once again, but this time with a more restricted
range of motion of the wrist.
A magnetic resonance imaging scan showed nonspecific expansion of the ulnar
styloid without evidence of a discernable mass
(Fig. 2). There was also no
evidence of a soft-tissue or periosteal lesion, and no medullary signal
changes were noted. A computed tomographic scan
(Fig. 3) revealed only cortical
irregularities along the distal aspect of the ulna and enlargement of the
ulnar styloid. The differential diagnosis at the time included periosteal
chondroma, osteochondroma, osteoid osteoma, giant-cell tumor, and chronic
stenosing tenosynovitis of the sixth extensor compartment. Because of the
increasing pain and limitation of function in conjunction with the
radiographic abnormalities seen at the distal aspect of the ulna, surgical
exploration was scheduled.
During the surgery, a localized cortical expansion at the base of the ulnar
styloid was identified. An en bloc excision of the mass was performed and
included a 1 to 2-mm margin of normal-appearing bone. The mass contained an
ovoid, pink, subcortical intramedullary lesion that measured approximately 8
mm at its longest dimension. Histologic evaluation of the mass showed bone
with a well-demarcated intramedullary tumor
(Fig. 4). The tumor cells were
predominantly spindle-shaped (Fig.
5), with a rate of mitosis between zero and four per ten
high-power fields and a mean mitotic count of two. There was moderate
cellularity and no necrosis. Immunochemistry revealed the tumor to be positive
for smooth-muscle actin and vimentin. The alpha-smooth-muscle actin stain was
strong, diffuse, and unequivocal. The tumor showed negative staining for AE1/3
(a broad-spectrum marker of epithelial cytokeratins), CD34 (a marker that is
often positive in mesenchymal tumors), CD117 (a marker that is commonly
positive in gastrointestinal stromal tumors), and S100 (a marker that is often
positive in tumors of nerve or nerve sheath or in those that originate from
melanomas). The tumor was also negative for MAC387 and CD68, which are
histiocytic markers and may be positive in fibrohistiocytic tumors. The
diagnosis of a benign intraosseous leiomyoma was made.
Two months after the operation, the patient had no pain in the wrist. There
was substantial improvement in the range of motion in all planes, with wrist
flexion to 65°, extension to 40°, and full pronation and supination.
Two years after surgery, there was no evidence of recurrence of the tumor.