AJR 2000; 175:1340
© American Roentgen Ray Society
Radiologic-Pathologic Conferences of The
University of Texas M. D.
Anderson Cancer Center |
Primary Liposarcoma of the Mediastinum
Reginald F. Munden1,
Jonathan C. Nesbitt2,
Bonnie L. Kemp3,4,
Marvin H. Chasen1 and
Gary J. Whitman1
1
Division of Diagnostic Imaging, The University of Texas M. D. Anderson Cancer
Center, Box 57, 1515 Holcombe Blvd., Houston, TX 77030.
2
Cardiovascular Surgery Associates, 4230 Harding Rd., Nashville, TN
37205.
3
Division of Pathology, The University of Texas M. D. Anderson Cancer Center,
1515 Holcombe Blvd., Houston, TX 77030.
4
Present address: Department of Pathology, Mayo Clinic, 200 First St. S.W.,
Rochester, MN 55905.
Received February 9, 2000;
accepted after revision May 17, 2000.
Address correspondence to R. F. Munden.
Introduction
A 56-year-old man with a history of melanoma of the left cheek was referred
for evaluation of mediastinal widening noted on chest radiography
(Fig. 1A). CT showed a large
low-density (-70 H) mediastinal mass surrounding and displacing the aorta and
trachea (Fig. 1B). At surgery,
an encapsulated mass was removed. The final pathologic diagnosis was
well-differentiated low-grade liposarcoma (atypical lipomatous tumor)
(Fig. 1C).
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Fig. 1B. —Primary liposarcoma of mediastinum in 56-year-old man. CT
scan shows large fatty mediastinal mass impinging on left innominate vein
(arrows) and causing deviation of trachea (arrowhead) to
right.
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Primary mediastinal liposarcomas are extremely rare, and they usually occur
in adults, with most cases occurring in patients more than 40 years old. Most
patients present with dyspnea, vague chest discomfort, cough, or
constitutional symptoms. Patients may present with signs of superior vena
caval obstruction, and as many as 15% of patients may be asymptomatic
[1].
Four main types of liposarcomas have been described: myxoid, well
differentiated, dedifferentiated, and pleomorphic. Evans
[2] reported that survival in
patients with dedifferentiated or pleomorphic liposarcomas was significantly
shorter than in patients with myxoid or well-differentiated liposarcomas.
Well-differentiated low-grade liposarcomas, also known as atypical lipomatous
tumors, have histologic features in many areas resembling mature adipose
tissue. Interspersed areas contain lipocytes that exhibit greater variation in
size and shape than the lipocytes observed in lipomas. Scattered cells in
these areas and in fibrous bands show atypical cytologic features. The
cytoplasm of the atypical cells is usually indistinct or amorphous, and
occasional cytoplasmic vacuoles are noted. Rarely, lipoblasts exhibit enlarged
hyperchromatic nuclei with peripheral indentations due to cytoplasmic vacuoles
[2].
The predominant finding of mediastinal liposarcoma on conventional chest
radiography is a widened mediastinum. Deviation of the trachea and vessels may
be apparent. On CT and MR imaging, mediastinal liposarcomas appear as
inhomogeneous fatty masses that vary in appearance depending on the amount of
soft tissue and fibrous bands in the tumor. The more solid components may
enhance with contrast material administration, and surrounding structures may
be infiltrated or displaced. These morphologic features along with a rapid
rate of growth and tracheal or vascular displacement should raise the
suspiction for liposarcoma
[3].
The recommended treatment for mediastinal liposarcoma is surgical excision
[4]. If the entire tumor cannot
be resected, surgical debulking often results in symptomatic relief. Radiation
therapy and chemotherapy may be added as adjuncts to surgical excision.
Approximately 40% of mediastinal liposarcomas recur after surgery
[1]. Multiple successive
recurrences are common [2].
These local recurrences are likely related to the inability to obtain adequate
complete excisions. Evans [2]
reported that atypical lipomatous tumors may transform into dedifferentiated
liposarcomas. Atypical lipomatous tumors usually do not metastasize
[2].
References
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Plukker JTM, Joosten HJM, Rensing JBM, Van Haelst UJGM. Primary
liposarcoma of the mediastinum in a child. J Surg
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Evans HL. Liposarcomas and atypical lipomatous tumors: a study of
66 cases followed for a minimum of 10 years. Surg
Pathol 1988;1:41
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Munk PL, Lee MJ, Janzen DL, et al. Lipoma and liposarcoma:
evaluation using CT and MR imaging. AJR
1997;169:589
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Grewal RG, Prager K, Austin JHM, Rotterdam H. Long term survival in
non-encapsulated primary liposarcoma of the mediastinum.
Thorax 1993;48
: 1276-1277[Abstract/Free Full Text]
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Introduction
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