ARTICLE
Auteur(s) :, Takeshi
Uenotsuchi1,2,*, Shinichi Imafuku1,2,
Yoichi Moroi2, Kazunori Urabe2, Masutaka
Furue2
1Department of Dermatology, Hiroshima Red Cross
Hospital and Atomic-bomb Survivors Hospital, Hiroshima, Japan Fax:
(+81) 92-642-5600.
2Department of Dermatology, Graduate School of Medical
Sciences, Kyushu University, Fukuoka 812-8582, Japan
accepté le 1 Juin 2004
Soft-tissue sarcomas arise wherever mesenchymal tissue is present
and can therefore develop in almost any part of the body. There are
several different types of soft-tissue sarcomas, of which
liposarcoma is the commonest. It accounts for approximately 20% of
these mesenchymal malignancies [1]. Liposarcomas originate from
primitive mesenchymal cells rather than mature fat cells, and
usually occur in the deep soft tissue of the extremities or the
retroperitoneum. By contrast, cutaneous and subcutaneous
liposarcoma are rare [2].
Case report
A 63-year-old man presented at our outpatient clinic with a large
mass located between the left lateral side of the chest wall and
the back. The patient had first recognized a very soft and painless
mass in the left lateral side of the chest wall four years earlier.
A physical examination revealed a very soft, non-tender and highly
mobile subcutaneous mass, with a diameter of about 20 cm (( figure 1 )). Magnetic
resonance imaging (MRI) confirmed the presence of a large
subcutaneous tumor (6 × 8 × 20 cm). It was well circumscribed and
traversed by septa, which were mostly thin but had irregular thick
areas. The tumor had the same signal intensity as subcutaneous fat
in T1- and T2-weighted sequences (( figure 2 )). Consequently,
it was considered that the tumor was derived from adipose tissue,
and therefore possibly benign, and an incisional biopsy was
performed. The tumor was found to be encapsulated by a fibrous
membrane, which lay under the subcutis. The biopsy specimen
revealed that, histologically, the tumor was composed of mature
adipose cells, which showed a slight variation in size and shape;
there were no atypical cells or lipoblasts (immature fat cells) ((
figure 3 )).
Therefore, based on the histological and MRI findings that had
failed to identify the presence of lipoblasts (the hallmarks of
liposarcoma), the tumor was diagnosed as a benign lipoma and
enucleation was planned.
Surgery revealed that the tumor was thinly encapsulated and
partially adhered to the underlying fascia of the lattissimus dorsi
muscle. The excised, gross tumor measured 16 × 14 × 10 cm, weighed
670 grams, and had a distinct lobulated shape (( figure 4 )).
Histologically, the tumor was formed from two components:
lipomatous lesion and fibrous bands. The lipomatous lesion was
composed of mature adipose cells, scattered among which atypical
cells, and more infrequently lipoblasts, could be identified. The
mature adipose cells showed a greater variation in size and shape
than was seen in the biopsy specimen. The atypical cells and
lipoblasts both had an irregular shape and hyperchromatic nuclei.
In addition, the lipoblasts had one or more lipid droplets in their
cytoplasm; scalloped-shaped nuclei were also observed in these
cells. The fibrous bands included areas of dense fibrosis,
fibroblast-like spindle cells, mature adipose cells, and more
lipoblasts (( figure
5 )). Based on the macroscopic and microscopic findings,
the tumor was ultimately diagnosed as a well-differentiated
liposarcoma, adipocytic type (lipoma-like type). Additional
resection was performed, including the underlying fascia of the
lattissimus dorsi muscle. The soft-tissue defect was covered with
split-skin grafts. No adjuvant therapy was given following the
surgical removal of the tumor. The patient remained free of local
recurrence or distant metastases for 24 months.
Discussion
Soft-tissue sarcomas are relatively uncommon and account for only
1% of all human malignancies [3]. Of the soft-tissue sarcomas
affecting adults, liposarcoma is one of the commonest, with an
incidence of about 20% among this type of tumor [4]. It is usually
located on the extremities, particularly the thigh, and the
retroperitoneum. The chest wall is a less common site, with only 3%
of all reported liposarcomas occurring at this location [5].
Liposarcomas usually arise from primitive mesenchymal tissue in the
deep soft tissue, such as intermuscular, fascial planes and similar
deep-seated vascular structures [5]. A liposarcoma, which arises
from subcutaneous tissue, is rare [2].
The World Health Organization has recently produced a
classification of soft-tissue sarcomas that recognizes five
liposarcoma categories: well-differentiated (which includes the
adipocytic, sclerosing and inflammatory subtypes),
dedifferentiated, myxoid, round-cell, and pleomorphic [6]. The
adipocytic subtype of well-differentiated liposarcoma is composed
of mature adipose cells, which exhibit a striking variation in cell
size, together with scattered lipoblasts, which have unusual,
irregularly shaped, hyperchromatic nuclei and one or more lipid
droplets in their cytoplasm. The presence of lipoblasts is an
important feature in the diagnosis of liposarcoma [7].
Nevertheless, in the adipocytic subtype of well-differentiated
liposarcoma, lipoblasts are rare. This could explain why, in the
incisional biopsy sample we took pre-surgery, we were unable to
identify any lipoblasts and how as a consequence, we initially
diagnosed the tumor as a lipoma [8]. It has been recognized
elsewhere that benign and malignant cases of soft-tissue sarcomas
can easily be confused, particularly when a diagnosis relies on
small biopsy samples [9].
MRI is very useful for distinguishing well-differentiated
liposarcoma from benign lipoma. The features of a
well-differentiated liposarcoma are the presence of thickened
septa, nodular and/or globular areas of nonadipose tissue within
the lesion, associated nonadipose masses, and a total amount of
nonadipose tissue that makes up more than 25% of the lesion [10,
11]. However, nodular or patchy nonadipose components have been
recognized in benign lipomas [11].
Histological type is one of the major factors influencing the
survival rate of patients diagnosed with this type of malignancy.
Other factors that influence survival are the location and size of
the tumor, and the completeness and accuracy of the surgical
excision. Survival rates are excellent for patients with
liposarcomas located in cutaneous or subcutaneous tissue [2].
In spite of a biopsy and the use of MRI (the recommended initial
diagnostic procedures), we were unable to diagnose our patient’s
tumor as liposarcoma before surgery. The tumor was removed using
marginal resection and because it was large, the defect after
removal was considerable. This required a split-thickness skin
graft. This procedure allows for the early detection of any local
recurrence because, as the graft is very thin, nodules can easily
be detected underneath without the need of an MRI.
Well-differentiated cutaneous and subcutaneous liposarcoma have
been associated with a good prognosis. Nevertheless, careful
follow-up is required to detect local recurrence, high-grade change
or dedifferentiation [2].
References
1 Dei Tos AP. Liposarcoma: new entities and evolving concepts.
Ann Diag Path 2000; 4: 252-66.
2 Dei Tos AP, Mentzel T, Fletcher CDM. Primary
liposarcoma of the skin: A rare neoplasm with unusual high grade
features. Am J Dermatopath 1998; 20: 332-8.
3 Parker SL, Tong T, Bolder W, et al. Cancer
statistics, 1996. Cancer J Clin 1996; 46: 5-27.
4 Enzinger FM, Weiss SW. In: Soft tissue tumors, 2nd
ed. St. Louis: Mosby, 1988: 346-82.
5 Enzinger FM, Weiss SW. In: Soft tissue tumors, 3rd
ed. St. Louis: Mosby, 1995: 431-66.
6 Weiss SW. Histologic typing of soft tissue tumors. World
health organization histological classification of tumors. Berlin:
Springer, 1994.
7 Collins BT, Gossner G, Martin DS, Boyd JH.
Fine needle aspiration biopsy of well-differentiated liposarcoma of
the neck in young female. Acta Cytol 1999; 43: 452-6.
8 Weiss FM, Goldblum JR. In: Enzinger and Weiss’s soft
tissue tumors, 4th ed. St. Louis: Mosby, 2001: 641-93.
9 Fletcher CDM. Soft tissue tumors. In: Fletcher CDM,
ed. Diagnositc histopathology of tumors 2nd ed. Edinburgh:
Churchill livingstone, 2000: 1473-540.
10 Kransdorf MJ, Bancroft LW, Peterson JJ,
et al. Imaging of fatty tumors: Distinction of lipoma and
well-differentiated liposarcoma. Radiology 2002; 224: 99-104.
11 Ohguri T, Aoki T, Hisaoka M, et al.
Differential diagnosis of benign peripheral lipoma from
well-differentiated liposarcoma on MR imaging: Comparison of
margins and internal characteristics useful? Am J Roentgenol 2003;
180: 1680-94.
|
Printable version
Version PDF
