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The differential imaging features of fat-containing tumors in the peritoneal cavity and retroperitoneum: the radiologic-pathologic correlation.

Shin NY, Kim MJ, Chung JJ, Chung YE, Choi JY, Park YN - Korean J Radiol (2010)

Bottom Line: At the same time, lesions that do not require immediate treatment are being incidentally found at an increasing rate with these same imaging techniques.Thus, the questions about the treatment methods have become increasingly important.Classifying lesions in terms of the necessity of performing surgical treatment can provide important information to clinicians, and this is the one of a radiologist's key responsibilities.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Severance Hospital, Yonsei University School of Medicine, Seoul, Korea.

ABSTRACT
There are a variety of fat-containing lesions that can arise in the intraperitoneal cavity and retroperitoneal space. Some of these fat-containing lesions, such as liposarcoma and retroperitoneal teratoma, have to be resected, although resection can be deferred for others, such as adrenal adenoma, myelolipoma, angiomyolipoma, ovarian teratoma, and lipoma, until the lesions become large or symptomatic. The third group tumors (i.e., mesenteric panniculitis and pseudolipoma of Glisson's capsule) require medical treatment or no treatment at all. Identifying factors such as whether the fat is macroscopic or microscopic within the lesion, the origin of the lesions, and the presence of combined calcification is important for narrowing the differential diagnosis. The development and wide-spread use of modern imaging modalities make identification of these factors easier so narrowing the differential diagnosis is possible. At the same time, lesions that do not require immediate treatment are being incidentally found at an increasing rate with these same imaging techniques. Thus, the questions about the treatment methods have become increasingly important. Classifying lesions in terms of the necessity of performing surgical treatment can provide important information to clinicians, and this is the one of a radiologist's key responsibilities.

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64-year-old man with pathologically proven retroperitoneal myxoid liposarcoma.A. Unenhanced transverse CT scan shows slightly inhomogeneous, hypoattenuated lesion compared with muscle, with mean CT number of 18 HU; range of attenuation was -34 HU to 66 HU. Note septae (arrow) within tumor.B. Transverse contrast-enhanced CT scan shows enhancing septae (arrow) and non-fatty tumor components (open arrow).C. Transverse T2-weighted MR image shows tumor to be hyperintense in relation to subcutaneous fat. Low signal intense septae (arrow) are also noted.D, E. Transverse gadolinium-enhanced, fat-saturated T1-weighted MR images show slowly progressive enhancement, which represents solid nature of tumor. Fibrous septae and non-fatty tumor components are markedly enhanced.F. Photograph of gross pathologic specimen shows encapsulated soft solid mass with myxoid cut surface and whitish fibrous areas. There is no definite necrotic area.G. Photomicrograph (Hematoxylin & Eosin staining, ×200) demonstrates arborizing capillaries (arrow) in myxoid background and adipocytic differentiation (open arrow) at periphery of lesion.
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Figure 2: 64-year-old man with pathologically proven retroperitoneal myxoid liposarcoma.A. Unenhanced transverse CT scan shows slightly inhomogeneous, hypoattenuated lesion compared with muscle, with mean CT number of 18 HU; range of attenuation was -34 HU to 66 HU. Note septae (arrow) within tumor.B. Transverse contrast-enhanced CT scan shows enhancing septae (arrow) and non-fatty tumor components (open arrow).C. Transverse T2-weighted MR image shows tumor to be hyperintense in relation to subcutaneous fat. Low signal intense septae (arrow) are also noted.D, E. Transverse gadolinium-enhanced, fat-saturated T1-weighted MR images show slowly progressive enhancement, which represents solid nature of tumor. Fibrous septae and non-fatty tumor components are markedly enhanced.F. Photograph of gross pathologic specimen shows encapsulated soft solid mass with myxoid cut surface and whitish fibrous areas. There is no definite necrotic area.G. Photomicrograph (Hematoxylin & Eosin staining, ×200) demonstrates arborizing capillaries (arrow) in myxoid background and adipocytic differentiation (open arrow) at periphery of lesion.

Mentions: The myxoid and round cell liposarcomas represent a morphologic continuum, and the histologic grading is based on the extent of the round cell component (4). Myxoid liposarcoma is the most common subtype of liposarcomas. Myxoid liposarcoma has a prominent myxoid stroma with or without delicate arborizing vasculature (4). The myxoid components show less attenuation than that of muscle on CT scans, with similar signal intensity to that of water, and they are hypointense compared with muscle on the T1-weighted images and hyperintense compared with fat on the T2-weighted spin-echo images. The fibrous septa within the myxoid components show low signal intensity on the T2-weighted MR images (6) (Fig. 2). Before contrast enhancement, the myxoid components show CT attenuation and MR signal intensity similar to that of fluid. Lacy, linear or amorphous regions of high signal intensity can be noted on the T1-weighted images and intermediate signal intensity can noted on the T2-weighted images, which represent intratumoral fat, and these features permit making the correct diagnosis. Recognition of chemical shift artifacts between the water- and fat-based components also facilitates an accurate diagnosis. After contrast enhancement, gradual reticular enhancement may be seen within the myxoid components. Although myxoid liposarcomas may appear to be cystic lesions before contrast enhancement, they can be correctly characterized as solid lesions on the contrast-enhanced images (2).


The differential imaging features of fat-containing tumors in the peritoneal cavity and retroperitoneum: the radiologic-pathologic correlation.

Shin NY, Kim MJ, Chung JJ, Chung YE, Choi JY, Park YN - Korean J Radiol (2010)

64-year-old man with pathologically proven retroperitoneal myxoid liposarcoma.A. Unenhanced transverse CT scan shows slightly inhomogeneous, hypoattenuated lesion compared with muscle, with mean CT number of 18 HU; range of attenuation was -34 HU to 66 HU. Note septae (arrow) within tumor.B. Transverse contrast-enhanced CT scan shows enhancing septae (arrow) and non-fatty tumor components (open arrow).C. Transverse T2-weighted MR image shows tumor to be hyperintense in relation to subcutaneous fat. Low signal intense septae (arrow) are also noted.D, E. Transverse gadolinium-enhanced, fat-saturated T1-weighted MR images show slowly progressive enhancement, which represents solid nature of tumor. Fibrous septae and non-fatty tumor components are markedly enhanced.F. Photograph of gross pathologic specimen shows encapsulated soft solid mass with myxoid cut surface and whitish fibrous areas. There is no definite necrotic area.G. Photomicrograph (Hematoxylin & Eosin staining, ×200) demonstrates arborizing capillaries (arrow) in myxoid background and adipocytic differentiation (open arrow) at periphery of lesion.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2864861&req=5

Figure 2: 64-year-old man with pathologically proven retroperitoneal myxoid liposarcoma.A. Unenhanced transverse CT scan shows slightly inhomogeneous, hypoattenuated lesion compared with muscle, with mean CT number of 18 HU; range of attenuation was -34 HU to 66 HU. Note septae (arrow) within tumor.B. Transverse contrast-enhanced CT scan shows enhancing septae (arrow) and non-fatty tumor components (open arrow).C. Transverse T2-weighted MR image shows tumor to be hyperintense in relation to subcutaneous fat. Low signal intense septae (arrow) are also noted.D, E. Transverse gadolinium-enhanced, fat-saturated T1-weighted MR images show slowly progressive enhancement, which represents solid nature of tumor. Fibrous septae and non-fatty tumor components are markedly enhanced.F. Photograph of gross pathologic specimen shows encapsulated soft solid mass with myxoid cut surface and whitish fibrous areas. There is no definite necrotic area.G. Photomicrograph (Hematoxylin & Eosin staining, ×200) demonstrates arborizing capillaries (arrow) in myxoid background and adipocytic differentiation (open arrow) at periphery of lesion.
Mentions: The myxoid and round cell liposarcomas represent a morphologic continuum, and the histologic grading is based on the extent of the round cell component (4). Myxoid liposarcoma is the most common subtype of liposarcomas. Myxoid liposarcoma has a prominent myxoid stroma with or without delicate arborizing vasculature (4). The myxoid components show less attenuation than that of muscle on CT scans, with similar signal intensity to that of water, and they are hypointense compared with muscle on the T1-weighted images and hyperintense compared with fat on the T2-weighted spin-echo images. The fibrous septa within the myxoid components show low signal intensity on the T2-weighted MR images (6) (Fig. 2). Before contrast enhancement, the myxoid components show CT attenuation and MR signal intensity similar to that of fluid. Lacy, linear or amorphous regions of high signal intensity can be noted on the T1-weighted images and intermediate signal intensity can noted on the T2-weighted images, which represent intratumoral fat, and these features permit making the correct diagnosis. Recognition of chemical shift artifacts between the water- and fat-based components also facilitates an accurate diagnosis. After contrast enhancement, gradual reticular enhancement may be seen within the myxoid components. Although myxoid liposarcomas may appear to be cystic lesions before contrast enhancement, they can be correctly characterized as solid lesions on the contrast-enhanced images (2).

Bottom Line: At the same time, lesions that do not require immediate treatment are being incidentally found at an increasing rate with these same imaging techniques.Thus, the questions about the treatment methods have become increasingly important.Classifying lesions in terms of the necessity of performing surgical treatment can provide important information to clinicians, and this is the one of a radiologist's key responsibilities.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Severance Hospital, Yonsei University School of Medicine, Seoul, Korea.

ABSTRACT
There are a variety of fat-containing lesions that can arise in the intraperitoneal cavity and retroperitoneal space. Some of these fat-containing lesions, such as liposarcoma and retroperitoneal teratoma, have to be resected, although resection can be deferred for others, such as adrenal adenoma, myelolipoma, angiomyolipoma, ovarian teratoma, and lipoma, until the lesions become large or symptomatic. The third group tumors (i.e., mesenteric panniculitis and pseudolipoma of Glisson's capsule) require medical treatment or no treatment at all. Identifying factors such as whether the fat is macroscopic or microscopic within the lesion, the origin of the lesions, and the presence of combined calcification is important for narrowing the differential diagnosis. The development and wide-spread use of modern imaging modalities make identification of these factors easier so narrowing the differential diagnosis is possible. At the same time, lesions that do not require immediate treatment are being incidentally found at an increasing rate with these same imaging techniques. Thus, the questions about the treatment methods have become increasingly important. Classifying lesions in terms of the necessity of performing surgical treatment can provide important information to clinicians, and this is the one of a radiologist's key responsibilities.

Show MeSH
Related in: MedlinePlus