UJMS 110 (3) bra

Upsala J Med Sci 110 (3): 259–266, 2005

Lipofibromatosis Arising in a Pediatric Forearm
-A Case Report-

Daizo Sasaki1, Masahito Hatori1, Masami Hosaka1, Mika Watanabe2,
Shoichi Kokubun1

1Department of Orthopaedic Surgery, Tohoku University School of Medicine, 1-1 Seiryomachi,
Aobaku, Sendai, Miyagi 980-8574

2Department of Pathology, Tohoku University School of Medicine, 1-1 Seiryomachi, Aobaku, Sendai,
Miyagi 980-8574

ABSTRACT

Lipofibromatosis is a rare pediatric tumour described by Fetsch et al. in 2000. There
have been few reports about this tumour and few descriptions of its imaging features.
We report a case of this tumour forming a slowly growing, painless mass arising in the
forearm of a ten-month-old boy. This is the first report of lipofibromatosis to present
the radiological findings before surgery. Plain radiography and computed tomography
demonstrated a tumour located just beneath the fascia. Ultrasonic study showed a
hyperechoic tumour of 33 x 30 x 7 mm in size. Magnetic resonance imaging demon-
strated a multilobular mass with high signal intensities on both T1 / T2 weighted
images. Macroscopically, the tumour was poorly marginated. Microscopically, the
tumour was composed of abundant adipose tissues transversed by fibroblastic bands.
The adipose tissue occupied over 70% of the tumour. Adipocytes and fibroblastic ele-
ment infiltrated into the normal skeletal muscle tissues. Recognition of this clinical
entity is needed, especially in cases of lipomatous tumours arising in pediatric hands
and feet.

INTRODUCTION

Lipofibromatosis is a rare pediatric tumour described by Fetsch et al. in 2000 [1].
Since then, there have been few reports about this tumour and few descriptions of
its image findings. We report a case of this tumour occurring in the forearm of an
infant together with the radiological and histological findings.

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Received 28 January 2005
Accepted 5 April 2005
Key words: lipofibromatosis, lipomatous tumour, infant, radiological finding

CASE REPORT

A ten-month-old boy was referred to our clinic with a painless and slow-growing
tumour in the right forearm. The tumour, 25 x 20 mm in size, had a smooth surface,
clear margin, and was soft. Initial plain radiogram showed a mass beneath the fascia
(Fig 1). Ultrasonic study showed a hyperechoic tumour of 25 x 22 x 6 mm in size.
During the follow-up for five months, the mass increased in size to 33 x 30 x 7 mm.
Computed tomography (CT) showed a tumour located just beneath the fascia, the
density of which was similar to the subcutaneous fat (Fig 2). Magnetic resonance
imaging (MRI) revealed a multilobular mass of homogenous high signal intensities
on both T1 / T2 weighted images.

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Fig 1. Plain radiogram showing soft tissue
swelling (arrow).

Radiological differential diagnosis was intramuscular lipoma, lipoblastoma, and
other kind of lipomatous tumours. An attempt was made at marginal excision, but
the tumour was found to be not encapsulated and to have continuity with the adja-
cent tissues. Removal of the tumour together with the surrounding normal muscles
was performed.

Grossly, the tumour, 30 x 25 x 10 mm in size, was a mass yellowish in color, soft
in consistency, and poorly demarcated, involving the muscle (Fig 4). Microscopic
examination revealed abundant adipose tissue transversed by fibroblastic bands (Fig
5a). The fibroblastic component had relatively high cellularity with an immature
appearance, no cellular atypia, and no nuclear pleomorphism (Fig 5b). The adipose
tissue occupied over 70% of the tumour. The adipocytes did not have lipoblastic
appearances. Univacuolated cells were present between the fibroblastic fascicles
and the mature adipocytes (Fig 5c). Around the margin, adipocytes and fibroblastic

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Fig 2. CT scan demonstrated a tumour just beneath the muscular fascia (arrow).

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Fig 3. MR images. a) T1 weighted image. b) T2 weighted image. The tumour had homogenously high
signal intensities on both T1 / T2 weighted images (arrow).

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cells infiltrated into the normal skeletal muscle tissue (Fig 5b). Immunohistochemi-
cal study showed that the fibroblastic cell exhibited immunoreactivity for S-100
(focal), CD99, CD34, alpha SMA (focal), HHF-35 (focal, weak), bcl-2 (focal,
weak). No reactivity was detected for EMA, melan A, HMB-45. Adipocytes exhib-
ited a strong immunoreactivity for S-100, but negative reactivities for the other anti-
bodies. The rate of positive immunoreactivity for Ki67 was about 7-8% in the areas
of fibroblastic components.

The tumour was diagnosed as lipofibromatosis. The patient has had no local
recurrence for one year after the operation.

Fig 4. Gross appearance of the specimen.

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DISCUSSION

Lipofibromatosis was proposed by Fetsch et al. in 2000. They classified it as a
tumour consisting of abundant adipose tissue with a spindled fibroblastic element
involving the septa of fat tissue. It forms a slowly growing painless mass, especially
arising in the hands and feet of children, and in some cases congenitally. The ages
ranged from 11 days to 12 years (median age, 1 year) at the time of initial biopsy or
resection. There was a more than 2:1 male predominance [1,3].

Histopathologically, adipose tissue is an integral component of this tumour, typi-
cally comprising more than 50% of the tumour. In the present case, the adipose tis-
sue occupied more than 70% of the tumour. On the other hand, true fibromatoses
exhibit a more solid, sheet-like growth of the fibroblastic element and do not con-
tain fat as an integral component [1,3]. Fetsch et al. described that lipofibromatosis
had been interpreted as a type of infantile or juvenile fibromatosis, a variant of
fibrous hamartoma of infancy, a calcifying aponeurotic fibroma, and a fibrosing
lipoblastoma. The image findings of this tumour were not described in their report.
An extensive survey of the literature revealed that there was only one case report of
recurrence presenting an intramuscular, poorly circumscribed, huge mass with calci-

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Fig 5. Histology of the specimen. a) Low-power view. Abundant fat involving dense fibrous tissue
was noted. b) High-power view of mature adipocytes and spindled fibroblastic element. The skeletal
muscle was remarkably infiltrated. c) Univacuolated cells were noted between them (arrow).

fication, showing heterogeneous MR signal intensities [2]. Our case is the first
report to present the image findings of lipofibromatosis before operation. The imag-
ing features of the present case were not different from those seen in lipomas,
although microscopically the tumour had a highly cellular fibroblastic component.
Therefore, it seems difficult to diagnose lipofibromatosis by its imaging features
alone. Fetsch et al. reported that 72% of such patients had regrowth of their tumour
or had persistent disease, and most of whom had been managed by incomplete
removal. Recognition of this clinical entity is needed, especially in cases of lipoma-
tous tumours arising in pediatric hands and feet.

REFERENCES

1. Fetsch JF, Miettinen M, Laskin WB, Michal M, Enzinger FM (2000) A clinicopathologic study
of 45 pediatric soft tissue tumours with an admixture of adipose tissue and fibroblastic element,
and a proposal for classification as lipofibromatosis. Am J Surg Pathol 24:1491-1500.

2. Herrmann BW, Dehner LP, Forsen JW Jr (2004) Lipofibromatosis presenting as a pediatric neck
mass. Int J Pediatr Otorhinolaryngol 68:1545-1549.

3. Miettinen M, Fetsch JF; (2002); Lipofibromatosis; In: Christopher DM, Fletcher K, Krishnan U,
Mertens F; World Health Organization Classification of tumours. Tumours of Soft Tissue and
Bone; IARCPress Lyon; 85.

Corresponding author: Masahito Hatori, M.D.
Department of Orthopaedic Surgery,
Tohoku University School of Medicine
1-1 Seiryomachi, Aobaku, Sendai, Miyagi 980-8574
Tel: 81-22-717-7242, Fax: 81-22-717-7248
Email: mailto:mhato@mail.tains.tohoku.ac.jp

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