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Published online before print May 30, 2002, 10.1148/radiol.2241011113
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(Radiology 2002;224:99-104.)
© RSNA, 2002


Musculoskeletal Imaging

Imaging of Fatty Tumors: Distinction of Lipoma and Well-differentiated Liposarcoma1

Mark J. Kransdorf, MD, Laura W. Bancroft, MD, Jeffrey J. Peterson, MD, Mark D. Murphey, MD, William C. Foster, MD and H. Thomas Temple, MD

1 From the Department of Radiology, Mayo Clinic, 4500 San Pablo Rd, Jacksonville, FL 32224-3899 (M.J.K., L.W.B., J.J.P.); Department of Radiologic Pathology, Armed Forces Institute of Pathology, Walter Reed Army Medical Center, Washington, DC (M.J.K., M.D.M.); Department of Radiology and Nuclear Medicine, Uniformed Services University of the Health Sciences, Bethesda, Md (M.D.M.); Department of Radiology, University of Maryland School of Medicine, Baltimore (M.D.M.); Department of Orthopedic Surgery, Medical College of Virginia, Virginia Commonwealth University, Richmond (W.C.F.); and Department of Orthopedics and Rehabilitation, University of Miami School of Medicine, Fla (H.T.T.). Received June 26, 2001; revision requested August 16; final revision received January 4, 2002; accepted January 23. Address correspondence to M.J.K. (e-mail: kransdorf.mark@mayo .edu).


    ABSTRACT
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
PURPOSE: To review the reliability of computed tomographic (CT) and magnetic resonance (MR) imaging features in distinguishing lipoma and well-differentiated liposarcoma.

MATERIALS AND METHODS: CT (n= 29) and MR (n = 40) images and radiographs (n = 28) of 60 patients with histologically verified fatty tumors (35 lipomas and 25 well-differentiated liposarcomas) were retrospectively reviewed in 31 females and 29 males (mean age, 56 years; age range, 1-88 years). Images were assessed for adipose tissue content, and nonfatty component was classified (thin and/or thick septa and nodular and/or globular components) as absent, mild, moderate, or pronounced. Also assessed were signal intensity and tissue attenuation of the fatty components and nonadipose elements.

RESULTS: Statistically significant imaging features favoring a diagnosis of liposarcoma included lesion larger than 10 cm (P < .001), presence of thick septa (P = .001), presence of globular and/or nodular nonadipose areas (P = .003) or masses (P = .001), and lesion less than 75% fat (P < .001). The most statistically significant radiologic predictors of malignancy were male sex, presence of thick septa, and associated nonadipose masses, which increased the likelihood of malignancy by 13-, nine-, and 32-fold, respectively. Both lipoma and liposarcoma demonstrated thin septa and regions of increased signal intensity on fluid-sensitive MR images.

CONCLUSION: A significant number of lipomas will have prominent nonadipose areas and will demonstrate an imaging appearance traditionally ascribed to well-differentiated liposarcoma. Features that suggest malignancy include increased patient age, large lesion size, presence of thick septa, presence of nodular and/or globular or nonadipose masslike areas, and decreased percentage of fat composition.

© RSNA, 2002

Index terms: Lipoma and lipomatosis, 40.363 • Lipoma and lipomatosis, CT, 40.1211 • Lipoma and lipomatosis, MR, 40.1214 • Liposarcoma, 40.371 • Liposarcoma, CT, 40.1211 • Liposarcoma, MR, 40.1214 • Soft tissues, neoplasms, 40.363, 40.371


    INTRODUCTION
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Lipomatous tumors are common and account for approximately half of all soft-tissue tumors in surgical series (13). The computed tomographic (CT) and magnetic resonance (MR) images of patients with fatty masses are usually sufficiently characteristic to suggest their lipomatous nature and often allow a specific diagnosis. The distinction between lipoma and well-differentiated liposarcoma, however, is a frequent diagnostic dilemma.

Lipoma is a benign mesenchymal tumor in which the lesion closely resembles normal fat. The resemblance is so great that the fat within a lipoma cannot be distinguished histologically from normal fat; however, there are biochemical and ultrastructural differences (1). Well-differentiated liposarcomas also resemble lipomas, although they tend to be larger, are often traversed by dense bands of collagen, have gelatinous areas, and have adipocytes that show greater variation in size than an ordinary lipoma (1). Additionally, well-differentiated liposarcomas contain enlarged adipocytes, atypical hyperchromatic cells with angular nuclei, and lipoblasts (1).

As there are histologic similarities between lipoma and well-differentiated liposarcoma, there are also considerable imaging similarities. The purpose of our study was to review the reliability of CT and MR imaging features in distinguishing lipoma and well-differentiated liposarcoma.


    MATERIALS AND METHODS
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
This investigational protocol was conducted with the approval of the Mayo Clinic Institutional Review Board, in accordance with the requirements for a retrospective review; informed patient consent was not required. We retrospectively reviewed CT and MR images of 60 patients with histologically confirmed well-differentiated fatty tumors: 35 lipomas and 25 well-differentiated liposarcomas. Higher-grade liposarcomas and dedifferentiated liposarcomas were excluded from the study group, as were benign mesenchymomas (lipomas with metaplastic bone and cartilage) and infiltrating lipomas. Patients were selected from the archives of the Mayo Clinic and chosen from a review of computer-generated patient diagnoses from January 1996 through December 2000, supplemented by cases from the archives of the Department of Radiologic Pathology, Armed Forces Institute of Pathology, Washington, DC.

Images reviewed included CT scans (in 29 patients; 15 with contrast material enhancement), MR images (in 40 patients, eight with contrast enhancement), and radiographs (in 28 patients). Radiologic features assessed included lesion size (greatest dimension) and location, presence or absence of intralesional calcification, and percentage of lesion appearing similar to host adipose tissue. A lesion was considered completely composed of adipose tissue if it demonstrated a signal intensity and character identical to that of the subcutaneous adipose tissue. The percentage of fat was graded from 0 to 4 as follows: 0 = 100% fat, 1 = 90%–99% fat, 2 = 75%–90% fat, 3 = 50%–75% fat, and 4 = 50% fat or less. Additionally, the presence and character of the nonadipose components of the lesion were categorized. The number and character of septa, globular and/or nodular areas, and associated masses were recorded. Septa were considered thin if they were uniform and no thicker than 2 mm. Those thicker than 2 mm or those that had focal thickening were considered thick. More irregular conglomerate areas were considered globular and/or nodular. These features were also quantified as absent, mild, moderate, or pronounced. The designation of mass was reserved for dominant focal nonadipose soft-tissue masses within the lesion, and the size of the mass was recorded. To ensure the greatest consistency in evaluation of imaging features, images were assessed by the senior author following determination of the grading criteria by means of consensus. Patient age and sex were also recorded, as was complaint at presentation. The presence and amount of "altered" fat was assessed. Altered fat was defined as lesional adipose tissue that demonstrated a poorly defined, slightly increased attenuation at CT or nonspecific signal intensity at MR imaging. Finally, the extent (none, mild, moderate, or intense) and character (homogeneous, heterogeous, or linear and/or septal) of gadolinium-based enhancement was evaluated.

Patient demographics and lesion location were compared by using the Wilcoxon rank sum test for continuous variables and the {chi}2 test for categorized variables. A multiple logistic regression model was built by using a stepwise selection method to assess which study variables best predicted patients with liposarcoma. Data analysis was performed with SAS software (SAS Institute, Cary, NC). A P value of .05 was considered to indicate a statistically significant difference.

Excised specimens were not available for review or for mapping correlation with images. Pathologic reports were reviewed for descriptive comments characterizing the nonadipose areas of the tumors.


    RESULTS
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Patient demographics and lesion location are shown in Table 1. Comparison of the age and sex distribution of patients with lipoma versus patients with liposarcoma was statistically significant, with P values of .005 and .04, respectively. Presenting symptoms were known in 24 of 35 patients with lipoma and in 20 of 25 patients with liposarcoma. A soft-tissue mass was overwhelmingly the most frequent chief complaint (89% of all patients), noted in 20 of 24 (83%) patients with lipoma and in 19 of 20 (95%) patients with liposarcoma. One 23-cm liposarcoma was identified as a thigh mass during evaluation for deep venous thrombosis, while the remaining patients with lipoma presented with pain and swelling, extremity enlargement, and paresthesia.


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TABLE 1. Patient Demographics and Lesion Location

 
Imaging features are provided in Table 2 and were determined at analysis of the available CT and MR images and radiographs, as indicated in the footnote. The average largest dimension of liposarcoma was almost twice that of lipoma, measuring approximately 23.5 cm (vs 12.5 cm), which was statistically significant (P < .001). Four lesions, all lipomas, were composed of tissue that was identical to subcutaneous adipose tissue on all images (Fig 1). Thin septa were seen in both lipoma and liposarcoma and were not statistically significant features (P = .11), while thick septa, nodular and/or globular areas, and associated masses (Fig 2) all were significant predictors of malignancy (P < .001, P = .003, and P = .001, respectively). Seventeen of 18 (94%) lesions with no thick septa, globular and/or nodular areas, or masses were lipomas. The presence of thick septa was statistically significant, being seen in 24 of 25 (96%) patients with liposarcoma (P < .001). The presence of nodular and/or globular areas was also significant, as was the presence of an associated soft-tissue mass, with 10 of 12 (83%) masses seen in patients with liposarcoma (P = .001).


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TABLE 2. Imaging Features

 


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Figure 1. Transverse T1-weighted spin-echo 500/20 (repetition time msec/echo time msec) MR image shows lipoma in the supinator muscle of a 45-year-old man. The lesion (*) has a signal intensity and character identical to that of the subcutaneous adipose tissue. T2-weighted images (not shown) showed identical findings.

 


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Figure 2a. Transverse MR images show liposarcoma in the posterior compartment of the thigh in a 62-year-old man. (a) T1-weighted spin-echo 533/14 and (b) fat-saturated T2-weighted turbo spin-echo 2,000/60 MR images show thin (arrowhead in a) and thick (arrows) septa, as well as a confluent globular area (*) of nonadipose tissue. The thin septa are not readily appreciated in b.

 


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Figure 2b. Transverse MR images show liposarcoma in the posterior compartment of the thigh in a 62-year-old man. (a) T1-weighted spin-echo 533/14 and (b) fat-saturated T2-weighted turbo spin-echo 2,000/60 MR images show thin (arrowhead in a) and thick (arrows) septa, as well as a confluent globular area (*) of nonadipose tissue. The thin septa are not readily appreciated in b.

 
Eighteen lipomas and liposarcomas demonstrated regions of increased signal intensity on fluid-sensitive MR images, seven (39%) of which were in benign lesions (Fig 3). Additionally, both benign and malignant lesions showed lipomatous areas that had increased signal intensity and/or tissue attenuation relative to that of subcutaneous fat. This altered fat appearance (Fig 4) was seen in 19 patients, five (26%) of whom had benign tumors. The number of patients in these groups was too small for statistical analysis. Eight patients were evaluated with contrast-enhanced MR imaging. Liposarcomas in four patients showed mild enhancement, while lipomas in four patients showed no enhancement.



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Figure 3a. MR images show lipoma in the posterior compartment of the thigh in a 48-year-old man. Corresponding coronal (a) T1-weighted spin-echo 633/14 and (b) conventional T2-weighted spin-echo 2,050/80 MR images show a large mass with prominent thin (arrowheads) and thick (arrows) septa. (c) Transverse short inversion time inversion-recovery 2,183/40/150 (inversion time msec) MR image shows confluent globular area (*) of increased signal intensity. The MR appearance of the lesion simulates a liposarcoma.

 


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Figure 3b. MR images show lipoma in the posterior compartment of the thigh in a 48-year-old man. Corresponding coronal (a) T1-weighted spin-echo 633/14 and (b) conventional T2-weighted spin-echo 2,050/80 MR images show a large mass with prominent thin (arrowheads) and thick (arrows) septa. (c) Transverse short inversion time inversion-recovery 2,183/40/150 (inversion time msec) MR image shows confluent globular area (*) of increased signal intensity. The MR appearance of the lesion simulates a liposarcoma.

 


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Figure 3c. MR images show lipoma in the posterior compartment of the thigh in a 48-year-old man. Corresponding coronal (a) T1-weighted spin-echo 633/14 and (b) conventional T2-weighted spin-echo 2,050/80 MR images show a large mass with prominent thin (arrowheads) and thick (arrows) septa. (c) Transverse short inversion time inversion-recovery 2,183/40/150 (inversion time msec) MR image shows confluent globular area (*) of increased signal intensity. The MR appearance of the lesion simulates a liposarcoma.

 


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Figure 4a. Coronal MR images show liposarcoma in the thigh of a 74-year-old man. (a) T1-weighted spin-echo 493/14 image shows irregular septa (arrows, a-c) with a large amount of altered fat that is most prominent in the proximal aspect of the mass (* in a-c). (b) Corresponding short inversion time inversion-recovery 5,542/60/150 image shows the nonadipose areas to have an increased signal intensity relative to that of fat. (c) Fat-saturated T1-weighted spin-echo 782/14 image obtained after administration of contrast material shows moderate heterogeneous enhancement of nonadipose areas.

 


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Figure 4b. Coronal MR images show liposarcoma in the thigh of a 74-year-old man. (a) T1-weighted spin-echo 493/14 image shows irregular septa (arrows, a-c) with a large amount of altered fat that is most prominent in the proximal aspect of the mass (* in a-c). (b) Corresponding short inversion time inversion-recovery 5,542/60/150 image shows the nonadipose areas to have an increased signal intensity relative to that of fat. (c) Fat-saturated T1-weighted spin-echo 782/14 image obtained after administration of contrast material shows moderate heterogeneous enhancement of nonadipose areas.

 


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Figure 4c. Coronal MR images show liposarcoma in the thigh of a 74-year-old man. (a) T1-weighted spin-echo 493/14 image shows irregular septa (arrows, a-c) with a large amount of altered fat that is most prominent in the proximal aspect of the mass (* in a-c). (b) Corresponding short inversion time inversion-recovery 5,542/60/150 image shows the nonadipose areas to have an increased signal intensity relative to that of fat. (c) Fat-saturated T1-weighted spin-echo 782/14 image obtained after administration of contrast material shows moderate heterogeneous enhancement of nonadipose areas.

 
The odds ratios (ie, that a specific feature favors a diagnosis of liposarcoma versus lipoma) are shown in Table 3. A final multiple logistic regression model is shown in Table 4. Male sex, thick septa, and larger masses were the most significant predictors of liposarcoma. After adjusting for these three variables, none of the others retained significance.


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TABLE 3. Odds Ratios for Features Favoring a Diagnosis of Liposarcoma versus Lipoma in 60 Patients

 

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TABLE 4. Multiple Logistic Regression Model for Predicting Liposarcoma

 
The nonadipose areas within lipomas were significant in 11 (31%) of 35 cases. Globular and/or nodular areas were seen in addition to the previously noted septa (Figs 2, 3c). In two (6%) patients, a dominant nonadipose area was seen, suggesting a dedifferentiated lesion. The nonadipose components were typically fat necrosis and associated calcification, fibrosis, inflammation, and areas of myxoid change and hibernoma.

Contrast-enhanced MR images were available in eight patients (four with lipomas and four with liposarcomas). One lipoma showed no enhancement, and three showed mild linear enhancement. The four liposarcomas showed mild to moderate enhancement (Fig 4). The presence or absence of calcification was determined only at review of radiographs and CT images and was assessed in 46 patients (27 with lipomas and 19 with liposarcomas). Calcification was three times more likely to occur in liposarcoma, being identified in six (32%) liposarcomas and three (11%) lipomas.


    DISCUSSION
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
For the purpose of our review, we have not distinguished between well-differentiated liposarcoma and atypical lipoma (atypical lipomatous tumor). It should be noted that the terms atypical lipoma and atypical intramuscular lipoma were introduced into the medical literature by Evans et al in 1979 (4). They argued that subcutaneous and intramuscular tumors with the histologic appearance of well-differentiated liposarcoma should be designated as atypical lipoma and atypical intramuscular lipoma, respectively, "because they do not constitute a sufficient danger to life to be considered sarcoma" (4). In 1988, Evans (5) grouped atypical lipoma and atypical intramuscular lipoma with well-differentiated liposarcoma under the designation of atypical lipomatous tumors, concluding that differences in behavior are related to tumor location rather than histologic appearance. In accordance with the suggestion of the World Health Organization, we use the term atypical lipoma only for subcutaneous extremity lesions, reserving the term well-differentiated liposarcoma for lesions in all remaining sites (1). We have included three subcutaneous lesions in our analysis of well-differentiated liposarcomas, since atypical lipomas and well-differentiated liposarcomas are histologically (and, hence, radiologically) indistinguishable.

In the current review, we have documented a wider spectrum of imaging features of lipoma than has been previously appreciated, to our knowledge, and we have identified causes of these imaging features. We have identified several statistically significant features to help distinguish lipoma from liposarcoma in most cases and have provided the odds ratios for these features. The most important of these features 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 composing more than 25% of the lesion.

The appearances of well-defined malignancies reviewed in the present study are similar to those reported previously (510)—slightly heterogeneous lipomatous masses, resembling lipoma, with nonadipose septal and swirled and/or irregular nodular areas with nonspecific signal intensities. Contrast enhancement of the nonadipose areas has been described as faint (10). Hosono et al (8) noted that the septal structures in liposarcoma were thick, had irregular widths, and had marked enhancement on fat-suppressed T1-weighted images following gadopentetate dimeglumine administration. In contradistinction, they found septa in lipoma to be thin with faint enhancement, suggesting that this pattern might be useful in distinguishing lipoma and liposarcoma. Although only a small number of patients were imaged with gadolinium-based enhancement, our results were relatively similar.

In contrast to liposarcoma, lipoma has been characterized as showing homogeneous fatty attenuation at CT and a homogeneous signal intensity identical to that of fat in all pulse sequences at MR imaging (7,11). In the current study, all four lesions that were composed completely of fat (identical in appearance to subcutaneous adipose tissue at imaging) were lipomas. To date, this is the most reliable feature in establishing the diagnosis of lipoma at imaging. Thin fibrous septa of low signal intensity on T1- and T2-weighted images may traverse the lesion, as may intermingled muscle (9,11,12). Lipomas may show varying margins—Matsumoto et al (11) identified well-defined margins in 12 of 17 patients with intramuscular lipomas and infiltrating margins in the remaining five.

In the present study, 11 (31%) of 35 lipomas showed marked nonadipose areas. The imaging features in these cases could not be mapped to the excised specimens; however, review of surgical and pathologic reports showed that they correlated with fat necrosis and associated calcification, fibrosis, inflammation, and myxoid change. Mature fat is subject to a variety of superimposed secondary inflammatory processes (13). These include not only lipase-induced fat necrosis, but also various forms of panniculitis or lipogranuloma formation that may form tumorlike masses (13). In the present study, masslike areas were present in two lipomas and suggested dedifferentiation. Although fat necrosis is well described in subcutaneous tissue, there are limited reports on fat necrosis in lipomatous tumors (14). We suspect that the high prevalence of these changes in our study likely reflect a referral bias, in that large lipomas or lesions with atypical imaging features are more likely to be excised and histologic findings referred for consultation. Well-differentiated liposarcoma has traditionally been separated radiologically from other subtypes of liposarcoma by means of the percentage of adipose tissue within the lesion. Well-differentiated liposarcoma is typically composed of more than 75% fat, while other histologic subtypes usually have less than 25% fat (15). Eleven (44%) of 25 liposarcomas and three (9%) of 35 lipomas in our study had less than 75% fat. This also likely reflects a referral bias.

In our review, benign lesions were significantly smaller than malignancies (P = .001), a relationship that has been shown previously in multiple studies (11,16). Patients with lipoma were also significantly younger than those with liposarcoma (P = .011), as previously reported (12).

Calcification was seen in six (24%) malignant and three (9%) benign lesions. Calcification was reported in three (23%) of 13 lipomas reported by Chew and Hudson (17), with no calcification identified in any of five liposarcomas. The benign calcifications in that report were associated with fat necrosis. Our experience would suggest that although calcification is not specific, it is seen with a greater prevalence in malignant lesions.

In summary, lipoma can be successfully distinguished from well-differentiated liposarcoma when it is completely composed of adipose tissue. A significant number of lipomas will have prominent nonadipose areas and demonstrate an imaging appearance traditionally ascribed to well-differentiated liposarcoma. Imaging features that suggest malignancy include increased patient age, large lesion size, presence of thick septa, presence of nodular and/or globular or nonadipose masslike areas, and decreased percentage of fat composition.


    ACKNOWLEDGMENTS
 
We thank Elizabeth J. Atkinson, MS, in the Department of Biostatistics, Mayo Clinic Rochester, Minn, for her assistance with the statistical analysis.


    FOOTNOTES
 
Author contributions: Guarantor of integrity of entire study, M.J.K.; study concepts and design, M.J.K., W.C.F., H.T.T.; literature research, M.J.K., L.W.B., J.J.P.; data acquisition and analysis/interpretation, M.J.K., L.W.B.; statistical analysis, M.J.K., L.W.B., J.J.P.; manuscript preparation, M.J.K., L.W.B., J.J.P.; manuscript definition of intellectual content, M.J.K.; manuscript editing, M.J.K., L.W.B., J.J.P.; manuscript revision/review and final version approval, all authors.

The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense.


    REFERENCES
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Weiss SW. Lipomatous tumors. In: Weiss SW, Brooks JSJ, eds. Soft tissue tumors. Baltimore, Md: Williams & Wilkins, 1996; 207-251.
  2. Rydholm A, Berg NO. Size, site and clinical incidence of lipoma: factors in the differential diagnosis of lipoma and sarcoma. Acta Orthop Scand 1983; 54:929-934.[Medline]
  3. Myhre-Jensen O. A consecutive 7-year series of 1331 benign soft tissue tumours: clinicopathologic data—comparison with sarcomas. Acta Ortop Scand 1981; 52:287-293.
  4. Evans HL, Soule EH, Winkelmann RK. Atypical lipoma, atypical intramuscular lipoma, and well-differentiated liposarcoma: a reappraisal of 30 cases formerly classified as well-differentiated liposarcoma. Cancer 1979; 43:574-584.[CrossRef][Medline]
  5. Evans HL. Liposarcomas and atypical lipomatous tumors: a study of 66 cases followed for a minimum of 10 years. Surg Pathol 1988; 1:41-54.
  6. London J, Kim EE, Wallace S, Shirkhoda A, Coan J, Evans H. MR imaging of liposarcoma: correlation of MR features and histology. J Comput Assist Tomogr 1989; 13:832-835.[Medline]
  7. Bush CH, Spanier SS, Gillespy T. Imaging of atypical lipomas of the extremities: report of three cases. Skeletal Radiol 1988; 17:472-475.[CrossRef][Medline]
  8. Hosono M, Kobayashi H, Fujimoto R, et al. Septum-like structure in lipoma and liposarcoma: MR imaging and pathologic correlation. Skeletal Radiol 1997; 26:150-154.[CrossRef][Medline]
  9. Munk PL, Lee MJ, Janzen DL, et al. Lipoma and liposarcoma: evaluation using CT and MR imaging. AJR Am J Roentgenol 1997; 169:589-594.[Free Full Text]
  10. Arkun R, Memis A, Akalin T, Ustun EE, Sabah D, Kandiloglu G. Liposarcoma of soft tissue: MRI findings with pathologic correlation. Skeletal Radiol 1997; 26:167-172.[CrossRef][Medline]
  11. Matsumoto K, Hukuda S, Ishizawa M, Chano T, Okabe H. MRI findings in intramuscular lipomas. Skeletal Radiol 1999; 28:145-152.[CrossRef][Medline]
  12. Kransdorf MJ, Murphey MD. Imaging of soft tissue tumors Philadelphia, Pa: Saunders, 1997; 3-36, 57–102.
  13. Enzinger FM, Weiss SW. Liposarcoma. In: Enzinger FM, Weiss SW, eds. Soft tissue tumors. 3rd ed. St Louis, Mo: Mosby, 1995; 431-466.
  14. Ramdial PK, Madaree A, Singh B. Membranous fat necrosis in lipomas. Am J Surg Pathol 1997; 2:841-846.[CrossRef]
  15. Jelinek JS, Kransdorf MJ, Shmookler BM, Aboulafia AJ, Malawer MM. Liposarcoma of the extremities: MR and CT findings in the histologic subtypes. Radiology 1993; 186:455-459.[Abstract/Free Full Text]
  16. Berquist TH, Ehman RL, King BF, Hodgman CG, Ilstrup DM. Value of MR imaging in differentiating benign from malignant soft-tissue masses: study of 95 lesions. AJR Am J Roentgenol 1990; 155:541-547.[Abstract/Free Full Text]
  17. Chew FS, Hudson TM. Radionuclide imaging of lipoma and liposarcoma. Radiology 1980; 136:741-745.[Abstract/Free Full Text]



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