A 35-year-old man visited us with a chief complaint of painful swelling of the finger.
A physical examination revealed a palpable mass, measuring approximately 2 cm×1 cm,
on the dorsoradial side of the base of the middle phalanx of the right index finger
([Fig. 1A]). Upon history taking, we found that the mass had formed 7 to 8 years before and
had since grown slowly. The mass had a firm, hard, discrete, and immobile consistency.
An X-ray revealed a translucent, osteolytic lesion at the base of the middle phalanx;
this lesion was eccentrically located to the cortex ([Fig. 1B]). The lesion was a mass with an ovoid shape and was parallel to the long axis of
the bone; it had a slightly marginal sclerotic border. Moreover, it exhibited expansile
growth to the adjacent soft tissue on the dorsoradial side. On the basis of these
findings, we made a 2-cm straight, longitudinal incision on the radial side of the
dorsum of the middle phalanx, thus confirming the presence of a bulging well-circumscribed
cartilaginous-appearing mass ([Fig. 2A]). We performed an extensive, aggressive curettage of the lesion. The resulting bony
defect was filled using iliac bone graft and screw fixation. In the resected specimen,
there was a yellowish-white lobulated mass of 2 cm×1 cm×1 cm in size ([Fig. 2B]). On histopathological examination the mass mainly had a myxomatous appearance and
was characterized by the lobular arrangement of stellate or spindle-shaped cells.
The lobule was well circumscribed by fine fibrous septa and was composed of the central
hypocellular area and the peripheral hypercellular area ([Fig. 3]). On the basis of these findings, we established a diagnosis of chondromyxoid fibroma
(CMF). In the 15-month postoperative follow-up, the patient underwent an uneventful
course without recurrent or metastatic episodes.
Fig. 1
Preoperative findings. (A) Clinical photograph of the right index finger with a visible
mass protruding from the dorsoradial side of the middle phalanx. (B) Preoperative
anteroposterior X-ray film of the right index finger reveals radiolucent tumor in
the metaphyseal-diaphyseal area of the middle phalanx.
Fig. 2
Intraoperative findings. (A) Incision planning with exposure of the mass. (B) Resected
specimen (2 cm×1 cm×1 cm).
Fig. 3
Histopathology and immunohistochemistry findings. The tumor shows alternating hypocellular
and hypercellular areas. The hypocellular areas form lobules composed of loosely arranged
cells in the gray-blue chondromyxoid matrix and surrounded by hypercellular spindle
cells (H&E, ×40).
CMF was first described by Jaffe and Lichtenstein in 1948, and it is a rare, slowly
growing benign bone tumor of cartilaginous origin. It accounts for less than 1% of
all the primary bone tumors and less than 2% of benign bone tumors. Approximately
80% of the total cases occur in individuals aged 36 years or younger. There is no
gender-related difference. To date, no definite etiologies have been documented. It
is known that approximately 75% of the total cases of CMF affect the bones of the
lower extremities. In particular, it occurs most frequently in the tibia and femur
around the knee joint. Thus far, its incidence in the hand has been described to be
very rare. Most cases of CMF typically originate from the metaphysis and may then
extend to the epiphysis and diaphysis. The most common clinical manifestations of
CMF include swelling and pain at the sites of primary tumor growth, but there are
also some asymptomatic cases. Plain radiography shows that CMF has a round-to-oval
medullary lesion with a well-defined margin and is parallel to the long axis of the
bone. The tumor with a thin scalloped, sclerotic border has an eccentric location
in the metaphysis and a translucent, osteolytic, bubbly appearance. Furthermore, it
shows a slightly expansile growth to the adjacent soft tissue. For establishing the
diagnosis of chondromyxoid fibroma, histopathological examinations are essential.
In a nutshell, CMF is a firm, white, lobulated, well-circumscribed solid tumor mass
that is sharply demarcated from the adjacent bone marrow. Light microscopy revealed
that CMF is composed of three zones: myxomatous, fibrous, and chondroid zones. Histopathologically,
it is characterized by the multilobular arrangement of stellate or spindle-shaped
cells in an abundant myxoid background or chondroid intracellular material. These
lobules are composed of the central hypocellular area and the peripheral hypercellular
area. Surgical excision is the first-line choice for chondromyxoid fibroma, for which
only simple curettage is performed or a bone graft is used for filling the cavitary
defect following curettage. Although variable depending on the reports, the recurrence
is estimated at approximately 25%. Postoperatively, regular follow-up including radiography
is necessary. A good prognosis of CMF has been documented. In addition, it has been
reported that CMF shows no distant metastasis [1],[2],[3],[4],[5].
