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Intraosseous LIPOMA.

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ARTHRITIS & RHEUMATISM
Vol. 40, No. 5, May 1997, pp 978-979
0 1997, American College of Rheumatology
978
RADIOLOGIC V I G N E m
INTRAOSSEOUS LIPOMA
MOHAMED ABO EL-ATTA, SIJSAN M. IVANCEVICH, and ETHAN M. BRAUNSTEIN
Clinical history
The patient, a 65-year-old man, presented with a
10-day history of pain and swelling of the right ankle. He
stated that he had a bone “c:yst” that had first been
discovered approximately 30 years earlier. Over this
30-year course, there were no intermittent symptoms.
On physical examination, norinal range of motion and
normal ambulation were observed. There was no pain,
tenderness, or swelling over the site of the lesion. The
symptoms were treated conservatively. Four months
later the pain and swelling had resolved, and physical
examination findings were normal.
Radiologic findings
A plain anteroposterior radiograph of the right
ankle (Figure 1) showed an expanding lytic lesion of the
distal tibia. Although the cortex was bowed, there was no
cortical breakthrough. There was no matrix calcification
or ossification, although some dystrophic calcification
was seen in the center of the lesion. Magnetic resonance
imaging (MRI) of the distal tibia (Figure 2) showed that
the mass had the same signal characteristics as the
surrounding fatty marrow, on both T1-weighted spinecho (Figure 2A) and inversion recovery (STIR) (Figure
2B) images. This latter pulse sequence suppressed all
signal from fat, and there was no signal within the lesion.
On the T1-weighted image, the dystrophic calcification
appeared as a signal void.
an 85-year-old woman (2). There is no sex predilection.
Although the lesion may involve the appendicular or
axial skeleton, the lower extremity is most commonly
affected, and -15% of cases involve the calcaneus (3).
Intraosseous lipoma probably represents a true
benign neoplasm of marrow adipose tissue (4), but it
may be hamartomatous (5). The common presence of
dystrophic calcification, as in our patient, suggests that
medullary fat infarction may also play some role in the
etiology (6). Most intraosseous lipomas are asymptomatic (7) and are found incidentally, as was the case in our
patient. There is only a very low potential for malignant
transformation (8).
Radiographically, the presentation typically is
that of a well-defined expanding lucent lesion with
Diagnosis: Intraosseous lipoma
Discussion
Intraosseous lipoma is very rare, comprising
<1% of all primary bone tumors (1). Most patients are
middle-aged, although the tumor has been reported in
Mohamed Abo El-Atta, MD: Mansoura University, Mansoura, Egypt; Susan M. Ivancevich, M[D, Ethan M. Braunstein, MD:
Indiana University Medical Center, Indianapolis.
Address reprint requests to E3than M. Braunstein, MD, Department of Radiology, Indiana University Hospital, 550 North University Boulevard, Indianapolis, IN 46202-5253.
Submitted for publication July 2, 1996; accepted in revised
form September 3, 1996.
Figure 1. Anteroposterior radiograph of the right ankle, showing an
expanding lytic lesion of the distal tibia with a small area of calcification in the center.
RADIOLOGIC VIGNETTE
979
Figure 2. A, Coronal T1-weighted spin-echo magnetic resonance image of the right ankle (repetition time [TR]
460 ms, echo time [TE] 11 ms). The signal of the lesion is as bright as the signal from the surrounding marrow
fat, indicating that the lesion also is composed of fat. There is an area of signal void (arrow) in the center of the
lesion, corresponding to the calcification on the plain radiograph. B, STIR coronal image of the right ankle (TR
1,500 ms, TE 30 ms, inversion time 80 ms). All signal from fat has been suppressed, including signal from the
lesion. This also indicates that the lesion is composed of the same type of tissue as the surrounding fatty marrow.
central calcification. Depending on the patient’s age and
the clinical setting, the differential diagnosis may include
giant cell tumor, aneurysmal bone cyst, chondromyxoid
fibroma, desmoplastic fibroma, and other slowly growing
lytic lesions. In our patient, MRI was performed to
establish the diagnosis. The bright signal on T1-weighted
images and the signal suppression on STIR images were
exactly what would be expected if the lesion were
composed of benign fatty tissue. There was no cortical
destruction or soft tissue mass. Computed tomography
may be useful in suspected intraosseous lipoma, since
the characteristic attenuation of fat will characterize the
tissue. The imaging findings in our patient were so
typical that biopsy was not thought to be necessary.
Of course, these MRI findings are not specific for
intraosseous lipoma, since any fatty tissue will have the
same signal characteristics. However, in our patient the
combination of plain radiographic and MRI findings was
sufficient to exclude medullary fat necrosis, bone infarction, and fatty degeneration of bone marrow. Liposarcoma may be excluded on the basis of the uniform
appearance of the fat without any inhomogeneity of the
intraosseous fat signal.
If intraosseous lipoma is suspected based on the
plain radiography results, MRI is a noninvasive way to
establish the presence of lesion composed exclusively of
intraosseous fat and to determine if there are any
aggressive characteristics that would suggest the need
for vigorous treatment.
REFERENCES
1. Huvos AG: Bone Tumors: Diagnosk, Treatment, and Prognosis.
Philadelphia, WB Saunders, 1990
2. Leeson MC, Kay D, Smith BS: Intraosseous lipoma. Clin Orthop
181~186-190,1983
3. Rosenblatt EM, Mollin J, Abdelwahab IF: Bilateral calcaneal
intraosseous lipomas: a case report. Mt Sinai J Med 57:174-176,
1990
4. Buckley SL, Burkus JK. Intraosseous symptoms of the ilium: a
report. Clin Orthop 228297-301, 1988
5. Chow LT, Lee KC: Intraosseous lipoma: a clinicopathologic study
of nine cases. Am J Surg Pathol 16:401-410, 1992
6. Bagnaud F, Thevoz F, Taillard W: Le lipome intraosseux, expression d’un infarctus chronique: a propos d’un cas. J Chir (Paris)
94:165-176, 1967
7. Hart JAL: Intraosseous lipoma. J Bone Joint Surg [Br] 55:624-632,
1973
8. Ross CF, Hadfield G: Primary osteo-liposarcoma of bone (malignant mesenchymoma): report of a case. J Bone Joint Surg [Br]
50Bz639-643, 1968
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