AJR 2003; 181:569-570
© American Roentgen Ray Society
Normal Intratumoral Lymph Node in a Patient with Lipoma Mimicking Liposarcoma
P. Petrow1,
C. Dromain1,
J. M. Guinebretière2 and
D. Vanel1
1 Service de Radiodiagnostic, Institut Gustave Roussy, 39, rue Camille
Desmoulins, 94805 Villejuif Cedex, France.
2 Service d'Anatomo-Pathologie, Institut Gustave Roussy, 94805 Villejuif Cedex,
France.
Received May 29, 2002;
accepted after revision December 31, 2002.
Address correspondence to P. Petrow.
Introduction
Lipoma is the most frequent benign soft-tissue tumor in adults and is
frequently found in subcutaneous, fatty, and muscular tissue; its imaging
features on CT and MR imaging have been documented extensively in the
literature [1,
2]. Images of lipoma show a
fat-containing mass with well-defined borders and homogeneous content.
Conversely, ill-defined borders, and especially nonfatty heterogeneous
content, indicate the high probability of malignant tumor (i.e., liposarcoma).
We describe a case of a heterogeneous, atypical liposarcoma-mimicking lipoma
in a 45-year-old woman in whom the heterogeneous portion of the tumor was in
fact a normal lymph node encased by the lipoma.
Case Report
A 45-year-old woman with increasing pain in the lower posterior aspect of
the neck associated with a slowly growing subcutaneous mass was referred to
our institution for the initial workup MR imaging (Figs.
1A–1B).
Imaging revealed a multilobulated, 7 x 5 cm, subcutaneous mass with a
fine regular capsule and intratumor septations. The mass was composed almost
entirely of fatty tissue except for the anterior part, in which a suspicious
contrast-enhancing, 6-mm dedifferentiated intratumor nodule was seen within
what appeared to be a slowly growing well-differentiated liposarcoma.
Large-core (14-gauge) CT-guided automated gun biopsy of both the suspicious
poorly differentiated nodular part of the tumor and the seemingly
well-differentiated part was performed
(Fig. 1C). Histologic analysis
of the biopsy specimen revealed a normal lymph node in the nodular part of the
tumor and normal adipocytes in the well-differentiated part, suggesting a
normal lymph node within a benign subcutaneous lipoma
(Fig. 1D). The patient
underwent a standard surgical resection, and definitive histologic analysis of
the operative specimen confirmed the preoperative diagnosis.
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Fig. 1A. —45-year-old woman with slowly growing subcutaneous mass. Axial
spin-echo T1-weighted MR image (TR/TE, 560/14) (A) and fast spin-echo
T2-weighted image (4200/108) (B) show large multilobular,
fat-containing nonenhancing mass (arrowheads) with small 6-mm early
and intensely enhancing nodule (not shown), hypointense on T1-weighted images
and hyperintense on T2-weighted images with hilum (arrow).
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Fig. 1B. —45-year-old woman with slowly growing subcutaneous mass. Axial
spin-echo T1-weighted MR image (TR/TE, 560/14) (A) and fast spin-echo
T2-weighted image (4200/108) (B) show large multilobular,
fat-containing nonenhancing mass (arrowheads) with small 6-mm early
and intensely enhancing nodule (not shown), hypointense on T1-weighted images
and hyperintense on T2-weighted images with hilum (arrow).
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Fig. 1C. —45-year-old woman with slowly growing subcutaneous mass. Axial CT
scan shows CT-guided percutaneous large-core biopsy of both apparent
dedifferentiated, nodular, nonfatty part of tumor, and supposed
well-differentiated part.
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Fig. 1D. —45-year-old woman with slowly growing subcutaneous mass.
Photomicrograph of biopsy specimen shows nodular and fatty tumor components.
Note normal architecture of lymph node (arrowheads) and normal
adipocytes (arrows) within lipomatous tumor. (H and E,
x100)
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Discussion
Liposarcoma is one of the most frequent malignant soft-tissue tumors in
adults [1]. It should be
suspected whenever a large (> 5 cm) fat-containing soft-tissue tumor is
found, especially when it is clinically associated with pain and rapid growth.
Tumor differentiation can be evaluated on both CT and MR imaging because
well-differentiated liposarcoma displays a hypointense fat-intensity (<
–20 H) mass on CT; the tumor shows signal intensities similar to those
of subcutaneous normal fat on MR images
[2]. On the other hand, poorly
differentiated liposarcoma displays tissue density on CT and low signal
intensity on spin-echo T1-weighted and high signal intensity on T2-weighted MR
images with intense early enhancement on dynamic acquisition contrast-enhanced
images. Both components can be associated to various degrees. The poorly
differentiated part of the tumor should be identified and histologically
confirmed before treatment because neoadjuvant chemotherapy may be indicated,
followed by en bloc wide excisional surgery
[3,
4].
In our patient, a normal intratumor lymph node was mimicking an
undifferentiated part of the tumor, which—to our knowledge—has
never been reported in the imaging literature.
Percutaneous imaging-guided biopsy can be proposed during the initial
workup of soft-tissue tumors to obtain adequate tissue samples before
treatment [3]. Multiple
imaging-guided passes are recommended because more biopsy samples
representative of the entire tumor can safely be obtained; imaging-guided
route-planning of the biopsy passes makes it easier to avoid necrosis and
protects vulnerable structures such as nerves and vessels. The MR imaging
features of normal lymph nodes are well known, especially as regards breast MR
imaging [5,
6]. Correlation of these
findings with those of the clinical examination and mammography allows an
accurate diagnosis in most cases. In our patient, although the pattern looked
typical for a lymph node retrospectively, it never occurred to anyone that it
might indeed be a lymph node until after the biopsy was performed. In our
patient, histologic analysis of the biopsy specimens confirmed a benign lipoma
with a normal intratumor lymph node, allowing the tumor to be downstaged and
submitted to less aggressive surgical treatment (enucleation).
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Introduction
Case Report
