(Radiographics. 1999;19:S131-S145.)
© RSNA, 1999
Unusual Appearances of Uterine Leiomyomas: MR Imaging Findings and Their Histopathologic Backgrounds1
Hiroyuki Ueda, MD ,
Kaori Togashi, MD ,
Ikuo Konishi, MD ,
Milliam L. Kataoka, MD,
Takashi Koyama, MD ,
Toshitaka Fujiwara, MD ,
Hisataka Kobayashi, MD ,
Shingo Fujii, MD and
Junji Konishi, MD
1 From the Departments of Nuclear Medicine and Diagnostic Imaging (H.U., M.L.K., T.K., T.F., J.K.), Diagnostic and Interventional Imageology (K.T., H.K.), and Gynecology and Obstetrics (I.K., S.F.), Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan. Recipient of a Certificate of Merit award for a scientific exhibit at the 1998 RSNA scientific assembly. Received February 2, 1999; revision requested March 3; final revision received April 26; accepted April 29. Address reprint requests to K.T.
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Abstract
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Typical appearances of uterine leiomyoma at magnetic resonance (MR) imaging are well established, and diagnosis is usually easy. However, cases that are extremely difficult to differentiate from other conditions are occasionally encountered. To understand the wide spectrum of MR imaging findings, such unusual appearances can be classified into three categories: degeneration and other histopathologic findings, specific types of unusual leiomyomas, and unusual growth patterns. The common types of degeneration are hyaline (>60% of cases), cystic (~4%), myxoid, and red. Edema is not a phenomenon of degeneration but is a common histopathologic finding (~50% of cases). Hemorrhage, necrosis, and calcification (~4% of cases) may also be observed. Specific types of unusual leiomyomas include lipoleiomyoma and myxoid leiomyoma, which may have MR imaging features characteristic enough to allow differentiation from other gynecologic and nongynecologic diseases. Intravenous leiomyomatosis, metastasizing leiomyoma, diffuse leiomyomatosis, and peritoneal disseminated leiomyomatosis represent unusual growth patterns; other unusual growth patterns are retroperitoneal growth, parasitic growth, and the pattern that may occur in cervical leiomyoma. Because leiomyomas are the most common gynecologic tumors and are exclusively benign, it is important to be familiar with the variety of MR imaging appearances of uterine leiomyomas to distinguish them from other significant diseases.
Index Terms: Leiomyoma, 854.315 • Uterine neoplasms, diagnosis, 854.315 • Uterine neoplasms, MR, 854.1214, 854.315
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INTRODUCTION
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Leiomyomas are by far the most common uterine tumors and the most common gynecologic tumors. Extremely prevalent, they occur in more than 20% of women older than 30 years (1,2). Their typical appearances at magnetic resonance (MR) imaging have been well established (3,4). However, leiomyomas vary widely in appearance and may be confused with other gynecologic malignancies. Precise knowledge of the histopathologic backgrounds of degeneration and the clinical course helps us accurately diagnose leiomyomas with unusual appearances.
In this article, the spectrum of MR imaging findings in uterine leiomyoma is presented with emphasis on the findings that help characterize the lesion. Unusual appearances are discussed from three points of view: MR imaging–histopathologic correlation, specific types of unusual leiomyomas, and unusual growth patterns.
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MR IMAGING-HISTOPATHOLOGIC CORRELATION
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Leiomyomas typically demonstrate distinct low signal intensity relative to that of the myometrium on T2-weighted images and intermediate signal intensity on T1-weighted images. These characteristic signal intensities are attributed to extensive hyalinization, which occurs in more than 60% of uterine leiomyomas (1,5,6). However, leiomyomas can demonstrate various histopathologic patterns of degeneration, some of which alter the MR imaging appearance. The common types of degeneration are hyaline, cystic, myxoid, and red. Edema is not a phenomenon of degeneration but is a common histopathologic finding, present in about 50% of leiomyomas (1). Hemorrhage, necrosis, and calcification may also be observed. In this section, a wide variety of MR imaging findings in uterine leiomyoma and their histopathologic backgrounds are described.
Degeneration
The most common type of degeneration is focal or generalized hyalinization. Hyalinization occurs in more than 60% of leiomyomas and is usually extensive (1,5,6). At the microscopic level, hyalinization begins in the stromal component that separates the smooth muscle cells and then progresses to extensive replacement of the smooth muscle cells (2). The typical MR imaging feature of leiomyoma—distinct low signal intensity on T2-weighted images—is due to extensive hyalinization (7,8) (Fig 1).
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Figure 1a. Typical leiomyoma in a 37-year-old woman. (a) Sagittal spin-echo T2-weighted MR image (2,000/70 [repetition time msec/echo time msec]) shows a well-demarcated mass of distinct low signal intensity with a speckled appearance. (b) Photograph of the cut surface of the resected lesion shows a white mass with a speckled appearance. (c) Photomicrograph (original magnification, x100; hematoxylin-eosin stain) shows hyaline degeneration throughout the lesion (*).
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Figure 1b. Typical leiomyoma in a 37-year-old woman. (a) Sagittal spin-echo T2-weighted MR image (2,000/70 [repetition time msec/echo time msec]) shows a well-demarcated mass of distinct low signal intensity with a speckled appearance. (b) Photograph of the cut surface of the resected lesion shows a white mass with a speckled appearance. (c) Photomicrograph (original magnification, x100; hematoxylin-eosin stain) shows hyaline degeneration throughout the lesion (*).
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Figure 1c. Typical leiomyoma in a 37-year-old woman. (a) Sagittal spin-echo T2-weighted MR image (2,000/70 [repetition time msec/echo time msec]) shows a well-demarcated mass of distinct low signal intensity with a speckled appearance. (b) Photograph of the cut surface of the resected lesion shows a white mass with a speckled appearance. (c) Photomicrograph (original magnification, x100; hematoxylin-eosin stain) shows hyaline degeneration throughout the lesion (*).
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Edema may change into various degrees of collagen deposition and cystic degeneration (6). Cystic degeneration may be considered an extreme sequela of edema and is observed in about 4% of leiomyomas (1). Large or small cystic spaces develop in the edematous, acellular center (1,5,6). The cystic spaces appear as round, well-demarcated areas with the signal intensity characteristic of fluid: low on T1-weighted images and high on T2-weighted images with no enhancement (Fig 2).
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Figure 2a. Subserosal leiomyoma with extensive cystic degeneration in a 61-year-old woman. (a, b) Sagittal spin-echo T1-weighted (600/25) (a) and T2-weighted (2,000/70) (b) MR images show a mass posterior to the uterus (U) (arrows). The signal intensity of the mass corresponds to fluid mixed with thin, interlacing tissue of intermediate signal intensity on both images. (c) Photograph of the cut surface of the resected lesion shows an almost entirely cystic mass with scanty solid tissue. (Reprinted, with permission, from reference 4.)
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Figure 2b. Subserosal leiomyoma with extensive cystic degeneration in a 61-year-old woman. (a, b) Sagittal spin-echo T1-weighted (600/25) (a) and T2-weighted (2,000/70) (b) MR images show a mass posterior to the uterus (U) (arrows). The signal intensity of the mass corresponds to fluid mixed with thin, interlacing tissue of intermediate signal intensity on both images. (c) Photograph of the cut surface of the resected lesion shows an almost entirely cystic mass with scanty solid tissue. (Reprinted, with permission, from reference 4.)
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Figure 2c. Subserosal leiomyoma with extensive cystic degeneration in a 61-year-old woman. (a, b) Sagittal spin-echo T1-weighted (600/25) (a) and T2-weighted (2,000/70) (b) MR images show a mass posterior to the uterus (U) (arrows). The signal intensity of the mass corresponds to fluid mixed with thin, interlacing tissue of intermediate signal intensity on both images. (c) Photograph of the cut surface of the resected lesion shows an almost entirely cystic mass with scanty solid tissue. (Reprinted, with permission, from reference 4.)
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Myxoid degeneration appears as soft mucoid areas, sometimes with cystic change (2). Leiomyomas with this type of degeneration are basically benign and appear as cystic masses filled with gelatinous material (Fig 3). However,
myxoid degeneration is important because it may also be seen in leiomyosarcomas and other malignant tumors (2). A tumor with extensive myxoid change may be diagnosed as myxoid leiomyoma, which is discussed later in this article (1,2).
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Figure 3a. Leiomyoma with myxoid degeneration in a 55-year-old woman. (a-c) Sagittal spin-echo T2-weighted (2,000/70) (a), T1-weighted (600/20) (b), and gadolinium-enhanced T1-weighted (600/20) (c) MR images show a mass arising from the uterine cervix that has mixed solid and cystic components. Myxoid material (arrowheads) demonstrates high signal intensity on the T2-weighted image (a), low signal intensity on the T1-weighted image (b), and no enhancement on the gadolinium-enhanced image (c). Viable tissue has relatively low signal intensity on the T2-weighted image (a) and is well enhanced on the gadolinium-enhanced image (c). (d) Photograph of the cut surface of the resected lesion shows a cystic mass filled with gelatinous material (arrowheads).
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Figure 3b. Leiomyoma with myxoid degeneration in a 55-year-old woman. (a-c) Sagittal spin-echo T2-weighted (2,000/70) (a), T1-weighted (600/20) (b), and gadolinium-enhanced T1-weighted (600/20) (c) MR images show a mass arising from the uterine cervix that has mixed solid and cystic components. Myxoid material (arrowheads) demonstrates high signal intensity on the T2-weighted image (a), low signal intensity on the T1-weighted image (b), and no enhancement on the gadolinium-enhanced image (c). Viable tissue has relatively low signal intensity on the T2-weighted image (a) and is well enhanced on the gadolinium-enhanced image (c). (d) Photograph of the cut surface of the resected lesion shows a cystic mass filled with gelatinous material (arrowheads).
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Figure 3c. Leiomyoma with myxoid degeneration in a 55-year-old woman. (a-c) Sagittal spin-echo T2-weighted (2,000/70) (a), T1-weighted (600/20) (b), and gadolinium-enhanced T1-weighted (600/20) (c) MR images show a mass arising from the uterine cervix that has mixed solid and cystic components. Myxoid material (arrowheads) demonstrates high signal intensity on the T2-weighted image (a), low signal intensity on the T1-weighted image (b), and no enhancement on the gadolinium-enhanced image (c). Viable tissue has relatively low signal intensity on the T2-weighted image (a) and is well enhanced on the gadolinium-enhanced image (c). (d) Photograph of the cut surface of the resected lesion shows a cystic mass filled with gelatinous material (arrowheads).
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Figure 3d. Leiomyoma with myxoid degeneration in a 55-year-old woman. (a-c) Sagittal spin-echo T2-weighted (2,000/70) (a), T1-weighted (600/20) (b), and gadolinium-enhanced T1-weighted (600/20) (c) MR images show a mass arising from the uterine cervix that has mixed solid and cystic components. Myxoid material (arrowheads) demonstrates high signal intensity on the T2-weighted image (a), low signal intensity on the T1-weighted image (b), and no enhancement on the gadolinium-enhanced image (c). Viable tissue has relatively low signal intensity on the T2-weighted image (a) and is well enhanced on the gadolinium-enhanced image (c). (d) Photograph of the cut surface of the resected lesion shows a cystic mass filled with gelatinous material (arrowheads).
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Red or carneous degeneration involves massive hemorrhagic infarction of a leiomyoma due to obstruction of drainage veins at the periphery of the lesion. Such degeneration is a kind of extensive coagulative necrosis that involves the entire lesion. This condition occurs most often during pregnancy and is also associated with use of oral contraceptives (1,5,6).
Unlike other types of degeneration, red degeneration usually causes systemic symptoms. Findings at MR imaging reflect the pathogenesis of this condition well and contribute to an accurate diagnosis (9). The peripheral rim, which has distinct low signal intensity on T2-weighted images and high signal intensity on T1-weighted images, corresponds to the obstructed veins at the periphery of the mass (Fig 4). The entire lesion shows no enhancement, which indicates complete interruption of blood flow.
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Figure 4a. Red degeneration in a 44-year-old woman with sudden onset of abdominal pain. (a) Sagittal fast spin-echo T2-weighted MR image (5,000/100) obtained several hours after onset shows a thick rim of distinct low signal intensity that corresponds to acute hemorrhage (arrows). (b) Sagittal spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows no significant findings. (c) Sagittal gadolinium-enhanced spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows complete absence of enhancement, a finding that indicates infarction. (d, e) Sagittal fast spin-echo T2-weighted (5,500/100) (d) and spin-echo T1-weighted (600/13) (e) MR images obtained 1 week later show a thick rim of distinct low signal intensity on the T2-weighted image (arrows in d) and high signal intensity on the T1-weighted image (arrows in e) that corresponds to subacute hemorrhage. (f,g)Permission to reprint these figures electronically was denied by the publisher. See print version.
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Figure 4b. Red degeneration in a 44-year-old woman with sudden onset of abdominal pain. (a) Sagittal fast spin-echo T2-weighted MR image (5,000/100) obtained several hours after onset shows a thick rim of distinct low signal intensity that corresponds to acute hemorrhage (arrows). (b) Sagittal spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows no significant findings. (c) Sagittal gadolinium-enhanced spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows complete absence of enhancement, a finding that indicates infarction. (d, e) Sagittal fast spin-echo T2-weighted (5,500/100) (d) and spin-echo T1-weighted (600/13) (e) MR images obtained 1 week later show a thick rim of distinct low signal intensity on the T2-weighted image (arrows in d) and high signal intensity on the T1-weighted image (arrows in e) that corresponds to subacute hemorrhage. (f,g)Permission to reprint these figures electronically was denied by the publisher. See print version.
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Figure 4c. Red degeneration in a 44-year-old woman with sudden onset of abdominal pain. (a) Sagittal fast spin-echo T2-weighted MR image (5,000/100) obtained several hours after onset shows a thick rim of distinct low signal intensity that corresponds to acute hemorrhage (arrows). (b) Sagittal spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows no significant findings. (c) Sagittal gadolinium-enhanced spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows complete absence of enhancement, a finding that indicates infarction. (d, e) Sagittal fast spin-echo T2-weighted (5,500/100) (d) and spin-echo T1-weighted (600/13) (e) MR images obtained 1 week later show a thick rim of distinct low signal intensity on the T2-weighted image (arrows in d) and high signal intensity on the T1-weighted image (arrows in e) that corresponds to subacute hemorrhage. (f,g)Permission to reprint these figures electronically was denied by the publisher. See print version.
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Figure 4d. Red degeneration in a 44-year-old woman with sudden onset of abdominal pain. (a) Sagittal fast spin-echo T2-weighted MR image (5,000/100) obtained several hours after onset shows a thick rim of distinct low signal intensity that corresponds to acute hemorrhage (arrows). (b) Sagittal spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows no significant findings. (c) Sagittal gadolinium-enhanced spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows complete absence of enhancement, a finding that indicates infarction. (d, e) Sagittal fast spin-echo T2-weighted (5,500/100) (d) and spin-echo T1-weighted (600/13) (e) MR images obtained 1 week later show a thick rim of distinct low signal intensity on the T2-weighted image (arrows in d) and high signal intensity on the T1-weighted image (arrows in e) that corresponds to subacute hemorrhage. (f,g)Permission to reprint these figures electronically was denied by the publisher. See print version.
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Figure 4e. Red degeneration in a 44-year-old woman with sudden onset of abdominal pain. (a) Sagittal fast spin-echo T2-weighted MR image (5,000/100) obtained several hours after onset shows a thick rim of distinct low signal intensity that corresponds to acute hemorrhage (arrows). (b) Sagittal spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows no significant findings. (c) Sagittal gadolinium-enhanced spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows complete absence of enhancement, a finding that indicates infarction. (d, e) Sagittal fast spin-echo T2-weighted (5,500/100) (d) and spin-echo T1-weighted (600/13) (e) MR images obtained 1 week later show a thick rim of distinct low signal intensity on the T2-weighted image (arrows in d) and high signal intensity on the T1-weighted image (arrows in e) that corresponds to subacute hemorrhage. (f,g)Permission to reprint these figures electronically was denied by the publisher. See print version.
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Figure 4f. Red degeneration in a 44-year-old woman with sudden onset of abdominal pain. (a) Sagittal fast spin-echo T2-weighted MR image (5,000/100) obtained several hours after onset shows a thick rim of distinct low signal intensity that corresponds to acute hemorrhage (arrows). (b) Sagittal spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows no significant findings. (c) Sagittal gadolinium-enhanced spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows complete absence of enhancement, a finding that indicates infarction. (d, e) Sagittal fast spin-echo T2-weighted (5,500/100) (d) and spin-echo T1-weighted (600/13) (e) MR images obtained 1 week later show a thick rim of distinct low signal intensity on the T2-weighted image (arrows in d) and high signal intensity on the T1-weighted image (arrows in e) that corresponds to subacute hemorrhage. (f,g)Permission to reprint these figures electronically was denied by the publisher. See print version.
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Figure 4g. Red degeneration in a 44-year-old woman with sudden onset of abdominal pain. (a) Sagittal fast spin-echo T2-weighted MR image (5,000/100) obtained several hours after onset shows a thick rim of distinct low signal intensity that corresponds to acute hemorrhage (arrows). (b) Sagittal spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows no significant findings. (c) Sagittal gadolinium-enhanced spin-echo T1-weighted MR image (600/13) obtained several hours after onset shows complete absence of enhancement, a finding that indicates infarction. (d, e) Sagittal fast spin-echo T2-weighted (5,500/100) (d) and spin-echo T1-weighted (600/13) (e) MR images obtained 1 week later show a thick rim of distinct low signal intensity on the T2-weighted image (arrows in d) and high signal intensity on the T1-weighted image (arrows in e) that corresponds to subacute hemorrhage. (f,g)Permission to reprint these figures electronically was denied by the publisher. See print version.
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Edema
Edema is not necessarily secondary to degeneration. Fluid accumulates for multiple reasons, and edema is a common histopathologic finding, observed in about 50% of leiomyomas. The presence of edema strongly affects the signal intensity of leiomyomas and may antedate hyalinization and cystic degeneration (1,5,6). The edema is scattered throughout the lesion in a speckled pattern but is frequently prominent at the periphery (10) (Fig 5). It is important to consider peripheral lymphedema in the diagnosis of leiomyoma, whereas central necrosis is a common finding in ovarian tumors. With extensive edema, the entire lesion has high signal intensity on T2-weighted images and demonstrates marked enhancement (11) (Fig 6). The high signal intensity on T2-weighted images is attributed to the accumulation of fluid, and the prominent enhancement is explained by retention of contrast material within the abundant interstitial spaces (11). At microscopy, fluid is seen in the stroma of the leiomyoma, often in association with collagen.
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Figure 5a. Leiomyoma consisting of a cellular component and peripheral edema in a 45-year-old woman. (a) Sagittal T2-weighted spin-echo MR image (2,000/70) shows a mass of intermediate signal intensity with a high-signal-intensity periphery (arrows). (b, c) Photomicrographs (original magnification, x20; hematoxylin-eosin stain) show tightly packed smooth muscle cells in the central zone (b) and prominent edema with large vessels at the periphery (c).
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Figure 5b. Leiomyoma consisting of a cellular component and peripheral edema in a 45-year-old woman. (a) Sagittal T2-weighted spin-echo MR image (2,000/70) shows a mass of intermediate signal intensity with a high-signal-intensity periphery (arrows). (b, c) Photomicrographs (original magnification, x20; hematoxylin-eosin stain) show tightly packed smooth muscle cells in the central zone (b) and prominent edema with large vessels at the periphery (c).
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Figure 5c. Leiomyoma consisting of a cellular component and peripheral edema in a 45-year-old woman. (a) Sagittal T2-weighted spin-echo MR image (2,000/70) shows a mass of intermediate signal intensity with a high-signal-intensity periphery (arrows). (b, c) Photomicrographs (original magnification, x20; hematoxylin-eosin stain) show tightly packed smooth muscle cells in the central zone (b) and prominent edema with large vessels at the periphery (c).
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Figure 6a. Leiomyoma with extensive edema in a 25-year-old woman. (a) Sagittal spin-echo T2-weighted MR image (2,000/70) shows a large mass of high signal intensity with scattered foci of low signal intensity arising from the uterus. (b, c) Sagittal nonenhanced (b) and gadolinium-enhanced (c) spin-echo T1-weighted MR images (600/20) show prominent enhancement of the entire mass except for small foci of cystic changes. (d) Photograph of the cut surface of the resected lesion shows a soft, pink mass. (e) Photomicrograph (original magnification, x20; hematoxylin-eosin stain) shows sparse smooth muscle cells (arrows) scattered within an area of extensive edema (*). No hyalin is present.
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Figure 6b. Leiomyoma with extensive edema in a 25-year-old woman. (a) Sagittal spin-echo T2-weighted MR image (2,000/70) shows a large mass of high signal intensity with scattered foci of low signal intensity arising from the uterus. (b, c) Sagittal nonenhanced (b) and gadolinium-enhanced (c) spin-echo T1-weighted MR images (600/20) show prominent enhancement of the entire mass except for small foci of cystic changes. (d) Photograph of the cut surface of the resected lesion shows a soft, pink mass. (e) Photomicrograph (original magnification, x20; hematoxylin-eosin stain) shows sparse smooth muscle cells (arrows) scattered within an area of extensive edema (*). No hyalin is present.
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Figure 6c. Leiomyoma with extensive edema in a 25-year-old woman. (a) Sagittal spin-echo T2-weighted MR image (2,000/70) shows a large mass of high signal intensity with scattered foci of low signal intensity arising from the uterus. (b, c) Sagittal nonenhanced (b) and gadolinium-enhanced (c) spin-echo T1-weighted MR images (600/20) show prominent enhancement of the entire mass except for small foci of cystic changes. (d) Photograph of the cut surface of the resected lesion shows a soft, pink mass. (e) Photomicrograph (original magnification, x20; hematoxylin-eosin stain) shows sparse smooth muscle cells (arrows) scattered within an area of extensive edema (*). No hyalin is present.
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Figure 6d. Leiomyoma with extensive edema in a 25-year-old woman. (a) Sagittal spin-echo T2-weighted MR image (2,000/70) shows a large mass of high signal intensity with scattered foci of low signal intensity arising from the uterus. (b, c) Sagittal nonenhanced (b) and gadolinium-enhanced (c) spin-echo T1-weighted MR images (600/20) show prominent enhancement of the entire mass except for small foci of cystic changes. (d) Photograph of the cut surface of the resected lesion shows a soft, pink mass. (e) Photomicrograph (original magnification, x20; hematoxylin-eosin stain) shows sparse smooth muscle cells (arrows) scattered within an area of extensive edema (*). No hyalin is present.
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Figure 6e. Leiomyoma with extensive edema in a 25-year-old woman. (a) Sagittal spin-echo T2-weighted MR image (2,000/70) shows a large mass of high signal intensity with scattered foci of low signal intensity arising from the uterus. (b, c) Sagittal nonenhanced (b) and gadolinium-enhanced (c) spin-echo T1-weighted MR images (600/20) show prominent enhancement of the entire mass except for small foci of cystic changes. (d) Photograph of the cut surface of the resected lesion shows a soft, pink mass. (e) Photomicrograph (original magnification, x20; hematoxylin-eosin stain) shows sparse smooth muscle cells (arrows) scattered within an area of extensive edema (*). No hyalin is present.
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Hemorrhage and Necrosis
Hemorrhage and necrosis (other than red degeneration) are not common but may be observed in leiomyomas. The recent trend in histopathologic diagnosis of leiomyosarcoma is to consider the presence of coagulative necrosis and hemorrhage (12). Thus, attention should be paid to hemorrhage and necrosis as clues in the diagnosis of sarcoma. However, red degeneration is an exception to this rule; furthermore, hemorrhage and necrosis do occur in some leiomyomas (Fig 7) (1,5,6,13). The damaged smooth muscle will eventually be replaced by firm collagenous tissue (1).
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Figure 7a. Cellular leiomyoma with coagulative necrosis in a 44-year-old woman. (a) Sagittal fast spin-echo T2-weighted MR image (6,000/126) shows a mass of relatively low signal intensity. Hemorrhage and necrosis are not obvious. (b, c) Sagittal nonenhanced (b) and gadolinium-enhanced (c) spin-echo T1-weighted MR images (600/9) show irregular areas of necrosis (arrows). The necrotic areas have high signal intensity on the T1-weighted image (b) and demonstrate no enhancement on the gadolinium-enhanced image (c). (d) Photograph of the cut surface of the resected lesion shows a fleshy mass with focal hemorrhage (arrows).
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Figure 7b. Cellular leiomyoma with coagulative necrosis in a 44-year-old woman. (a) Sagittal fast spin-echo T2-weighted MR image (6,000/126) shows a mass of relatively low signal intensity. Hemorrhage and necrosis are not obvious. (b, c) Sagittal nonenhanced (b) and gadolinium-enhanced (c) spin-echo T1-weighted MR images (600/9) show irregular areas of necrosis (arrows). The necrotic areas have high signal intensity on the T1-weighted image (b) and demonstrate no enhancement on the gadolinium-enhanced image (c). (d) Photograph of the cut surface of the resected lesion shows a fleshy mass with focal hemorrhage (arrows).
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Figure 7c. Cellular leiomyoma with coagulative necrosis in a 44-year-old woman. (a) Sagittal fast spin-echo T2-weighted MR image (6,000/126) shows a mass of relatively low signal intensity. Hemorrhage and necrosis are not obvious. (b, c) Sagittal nonenhanced (b) and gadolinium-enhanced (c) spin-echo T1-weighted MR images (600/9) show irregular areas of necrosis (arrows). The necrotic areas have high signal intensity on the T1-weighted image (b) and demonstrate no enhancement on the gadolinium-enhanced image (c). (d) Photograph of the cut surface of the resected lesion shows a fleshy mass with focal hemorrhage (arrows).
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Figure 7d. Cellular leiomyoma with coagulative necrosis in a 44-year-old woman. (a) Sagittal fast spin-echo T2-weighted MR image (6,000/126) shows a mass of relatively low signal intensity. Hemorrhage and necrosis are not obvious. (b, c) Sagittal nonenhanced (b) and gadolinium-enhanced (c) spin-echo T1-weighted MR images (600/9) show irregular areas of necrosis (arrows). The necrotic areas have high signal intensity on the T1-weighted image (b) and demonstrate no enhancement on the gadolinium-enhanced image (c). (d) Photograph of the cut surface of the resected lesion shows a fleshy mass with focal hemorrhage (arrows).
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Calcification
Secondary calcification occurs in hyalinized tissue in about 4% of leiomyomas (1). The calcification is usually dense and amorphous. This pattern of calcification at plain radiography almost exclusively indicates the diagnosis of leiomyoma. A rarely observed pattern is ringlike calcification at the margins of a leiomyoma (Fig 8). This type of calcification appears to represent thrombosed veins from past red degeneration.
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Figure 8a. Leiomyoma with ring calcification (probably a sequela of red degeneration) in a 42-year-old woman. The patient had experienced acute abdominal symptoms during her last pregnancy, which were indicative of red degeneration. (a, b) Sagittal fast spin-echo T2-weighted (6,000/126) (a) and spin-echo T1-weighted (600/9) (b) MR images show a mass with a distinct rim of low signal intensity (arrowheads). (c) Gadolinium-enhanced spin-echo T1-weighted MR image (600/9) shows complete absence of enhancement.
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Figure 8b. Leiomyoma with ring calcification (probably a sequela of red degeneration) in a 42-year-old woman. The patient had experienced acute abdominal symptoms during her last pregnancy, which were indicative of red degeneration. (a, b) Sagittal fast spin-echo T2-weighted (6,000/126) (a) and spin-echo T1-weighted (600/9) (b) MR images show a mass with a distinct rim of low signal intensity (arrowheads). (c) Gadolinium-enhanced spin-echo T1-weighted MR image (600/9) shows complete absence of enhancement.
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Figure 8c. Leiomyoma with ring calcification (probably a sequela of red degeneration) in a 42-year-old woman. The patient had experienced acute abdominal symptoms during her last pregnancy, which were indicative of red degeneration. (a, b) Sagittal fast spin-echo T2-weighted (6,000/126) (a) and spin-echo T1-weighted (600/9) (b) MR images show a mass with a distinct rim of low signal intensity (arrowheads). (c) Gadolinium-enhanced spin-echo T1-weighted MR image (600/9) shows complete absence of enhancement.
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SPECIFIC TYPES OF UNUSUAL LEIOMYOMAS
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There are specific types of unusual uterine leiomyomas. These include lipoleiomyoma, myxoid leiomyoma, intravenous leiomyomatosis, metastasizing leiomyoma, diffuse leiomyomatosis, and peritoneal disseminated leiomyomatosis (1,2). The first two types may have MR imaging findings characteristic enough to allow diagnosis and are discussed in this section. The other four types represent unusual growth patterns and are discussed in the next section.
Lipoleiomyoma
Lipoleiomyoma is a specific type of leiomyoma that contains a substantial amount of fat. The reported prevalence of lipoleiomyoma is 0.8% (14). At microscopy, circumscribed areas of adipocytes are seen within the leiomyoma. Angiolipoleiomyoma and lipoma are related lesions and are categorized according to their microscopic components. All of these lesions are considered to represent fatty metamorphosis of leiomyoma (1,5,6), although some tumors have no smooth muscle component. At MR imaging, the fatty tissue demonstrates signal intensity similar to that of subcutaneous fat with all pulse sequences (Fig 9) (15). The fat component is usually easily differentiated from hemorrhage because of the chemical shift. However, such differentiation is sometimes difficult. In these instances, chemical shift imaging is helpful in distinguishing fat from hemorrhage.
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Figure 9a. Lipoleiomyoma in a 76-year-old woman. (a-c) Sagittal fast spin-echo T2-weighted (3,000/120) (a) and spin-echo T1-weighted (400/25) (b) MR images and gadolinium-enhanced spin-echo T1-weighted MR image (400/25) obtained with fat suppression (c) show a mass (arrows) with signal intensity equal to that of subcutaneous fat. (d) Photograph of the cut surface of the resected lesion shows a soft, yellow mass. (e) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows numerous adipocytes in the mass. (Fig 9a-9e courtesy of Tsuyoshi Itoh, MD, Kyoto National Hospital, Kyoto, Japan.)
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Figure 9b. Lipoleiomyoma in a 76-year-old woman. (a-c) Sagittal fast spin-echo T2-weighted (3,000/120) (a) and spin-echo T1-weighted (400/25) (b) MR images and gadolinium-enhanced spin-echo T1-weighted MR image (400/25) obtained with fat suppression (c) show a mass (arrows) with signal intensity equal to that of subcutaneous fat. (d) Photograph of the cut surface of the resected lesion shows a soft, yellow mass. (e) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows numerous adipocytes in the mass. (Fig 9a-9e courtesy of Tsuyoshi Itoh, MD, Kyoto National Hospital, Kyoto, Japan.)
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Figure 9c. Lipoleiomyoma in a 76-year-old woman. (a-c) Sagittal fast spin-echo T2-weighted (3,000/120) (a) and spin-echo T1-weighted (400/25) (b) MR images and gadolinium-enhanced spin-echo T1-weighted MR image (400/25) obtained with fat suppression (c) show a mass (arrows) with signal intensity equal to that of subcutaneous fat. (d) Photograph of the cut surface of the resected lesion shows a soft, yellow mass. (e) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows numerous adipocytes in the mass. (Fig 9a-9e courtesy of Tsuyoshi Itoh, MD, Kyoto National Hospital, Kyoto, Japan.)
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Figure 9d. Lipoleiomyoma in a 76-year-old woman. (a-c) Sagittal fast spin-echo T2-weighted (3,000/120) (a) and spin-echo T1-weighted (400/25) (b) MR images and gadolinium-enhanced spin-echo T1-weighted MR image (400/25) obtained with fat suppression (c) show a mass (arrows) with signal intensity equal to that of subcutaneous fat. (d) Photograph of the cut surface of the resected lesion shows a soft, yellow mass. (e) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows numerous adipocytes in the mass. (Fig 9a-9e courtesy of Tsuyoshi Itoh, MD, Kyoto National Hospital, Kyoto, Japan.)
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Figure 9e. Lipoleiomyoma in a 76-year-old woman. (a-c) Sagittal fast spin-echo T2-weighted (3,000/120) (a) and spin-echo T1-weighted (400/25) (b) MR images and gadolinium-enhanced spin-echo T1-weighted MR image (400/25) obtained with fat suppression (c) show a mass (arrows) with signal intensity equal to that of subcutaneous fat. (d) Photograph of the cut surface of the resected lesion shows a soft, yellow mass. (e) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows numerous adipocytes in the mass. (Fig 9a-9e courtesy of Tsuyoshi Itoh, MD, Kyoto National Hospital, Kyoto, Japan.)
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Myxoid Leiomyoma
Relatively rare, myxoid leiomyomas contain abundant myxoid material between smooth muscle cells. The lesions are soft and translucent but solid. Large myxoid leiomyomas may be clinically malignant even if they do not meet standard criteria for the diagnosis of sarcoma. In these lesions, smooth muscle cells are so widely separated by abundant myxoid material that mitotic count and cellularity cannot be assessed precisely (1,5,6). At MR imaging, the myxoid portion has high signal intensity on T2-weighted images and enhances well except for small foci of mucinous lakes or clefts (Fig 10). Delayed and prolonged enhancement is seen because of the presence of a myxoid stroma (16).
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Figure 10a. Myxoid leiomyoma (smooth muscle tumor of uncertain malignant potential) in a 50-year-old woman. (a, b) Sagittal spin-echo T2-weighted (2,000/70) (a) and T1-weighted (600/20) (b) MR images show a huge mass with signal intensity similar to that of fluid: high on the T2-weighted image (a) and low on the T1-weighted image (b). (c) Sagittal gadolinium-enhanced spin-echo T1-weighted MR image (600/20) shows prominent enhancement of the lesion except for small foci of mucinous lakes (arrowheads). (d) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows nuclear atypia. Smooth muscle cells are so widely separated by abundant myxoid material that mitotic count and cellularity cannot be assessed precisely.
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Figure 10b. Myxoid leiomyoma (smooth muscle tumor of uncertain malignant potential) in a 50-year-old woman. (a, b) Sagittal spin-echo T2-weighted (2,000/70) (a) and T1-weighted (600/20) (b) MR images show a huge mass with signal intensity similar to that of fluid: high on the T2-weighted image (a) and low on the T1-weighted image (b). (c) Sagittal gadolinium-enhanced spin-echo T1-weighted MR image (600/20) shows prominent enhancement of the lesion except for small foci of mucinous lakes (arrowheads). (d) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows nuclear atypia. Smooth muscle cells are so widely separated by abundant myxoid material that mitotic count and cellularity cannot be assessed precisely.
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Figure 10c. Myxoid leiomyoma (smooth muscle tumor of uncertain malignant potential) in a 50-year-old woman. (a, b) Sagittal spin-echo T2-weighted (2,000/70) (a) and T1-weighted (600/20) (b) MR images show a huge mass with signal intensity similar to that of fluid: high on the T2-weighted image (a) and low on the T1-weighted image (b). (c) Sagittal gadolinium-enhanced spin-echo T1-weighted MR image (600/20) shows prominent enhancement of the lesion except for small foci of mucinous lakes (arrowheads). (d) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows nuclear atypia. Smooth muscle cells are so widely separated by abundant myxoid material that mitotic count and cellularity cannot be assessed precisely.
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Figure 10d. Myxoid leiomyoma (smooth muscle tumor of uncertain malignant potential) in a 50-year-old woman. (a, b) Sagittal spin-echo T2-weighted (2,000/70) (a) and T1-weighted (600/20) (b) MR images show a huge mass with signal intensity similar to that of fluid: high on the T2-weighted image (a) and low on the T1-weighted image (b). (c) Sagittal gadolinium-enhanced spin-echo T1-weighted MR image (600/20) shows prominent enhancement of the lesion except for small foci of mucinous lakes (arrowheads). (d) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows nuclear atypia. Smooth muscle cells are so widely separated by abundant myxoid material that mitotic count and cellularity cannot be assessed precisely.
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UNUSUAL GROWTH PATTERNS
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Consistent with their benignity, leiomyomas have a "pushing" (instead of infiltrating) border and are rounded. However, several specific types of leiomyoma—intravenous leiomyomatosis, metastasizing leiomyoma, diffuse leiomyomatosis, and peritoneal disseminated leiomyomatosis—are exceptions to this rule. Other unusual growth patterns are retroperitoneal growth and parasitic growth. An unusual growth pattern may also occur in cervical leiomyoma.
Intravenous Leiomyomatosis, Metastasizing Leiomyoma, Diffuse Leiomyomatosis, and Peritoneal Disseminated Leiomyomatosis
Otherwise morphologically unremarkable types of leiomyoma, intravenous leiomyomatosis, metastasizing leiomyoma, diffuse leiomyomatosis, and peritoneal disseminated leiomyomatosis represent only variations in growth patterns. Although histologically benign, these leiomyomas grow into veins, metastasize to distant organs, diffuse throughout the uterine parenchyma, or disseminate throughout the peritoneal cavity.
Intravenous leiomyomatosis is a rare condition characterized by growth of smooth muscle cells into the myometrial or pelvic veins. Convoluted, wormlike masses growing within the veins are the hallmark of intravenous leiomyomatosis (Fig 11) (17,18).
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Figure 11a. Intravenous leiomyomatosis in a 44-year-old woman. (a, b) Sagittal fast spin-echo T2-weighted MR images (6,000/135) show an ill-defined, subserosal mass of low signal intensity (arrows in a) with multiple wormlike projections that extensively involve the myometrium, parametrium, adnexa, and gonadal veins (large arrowheads in a, arrowheads in b). The wormlike projections are accompanied by prominent signal voids (small arrowheads in a). (c) Photograph of the resected specimen shows the subserosal tumor (arrows) and wormlike projections (arrowheads).
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Figure 11b. Intravenous leiomyomatosis in a 44-year-old woman. (a, b) Sagittal fast spin-echo T2-weighted MR images (6,000/135) show an ill-defined, subserosal mass of low signal intensity (arrows in a) with multiple wormlike projections that extensively involve the myometrium, parametrium, adnexa, and gonadal veins (large arrowheads in a, arrowheads in b). The wormlike projections are accompanied by prominent signal voids (small arrowheads in a). (c) Photograph of the resected specimen shows the subserosal tumor (arrows) and wormlike projections (arrowheads).
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Figure 11c. Intravenous leiomyomatosis in a 44-year-old woman. (a, b) Sagittal fast spin-echo T2-weighted MR images (6,000/135) show an ill-defined, subserosal mass of low signal intensity (arrows in a) with multiple wormlike projections that extensively involve the myometrium, parametrium, adnexa, and gonadal veins (large arrowheads in a, arrowheads in b). The wormlike projections are accompanied by prominent signal voids (small arrowheads in a). (c) Photograph of the resected specimen shows the subserosal tumor (arrows) and wormlike projections (arrowheads).
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Benign metastasizing leiomyoma consists of smooth muscle tumors in the lungs, lymph nodes, or abdomen that appear to originate from a benign uterine leiomyoma, which typically was removed many years earlier. Because the primary tumor often has been inadequately studied, this condition is still controversial.
Diffuse leiomyomatosis involves development of innumerable small leiomyomas, which produce symmetric enlargement of the uterus. In this condition, the leiomyomas replace most of the uterine parenchyma.
Peritoneal disseminated leiomyomatosis is characterized by multiple smooth muscle nodules on the peritoneal surfaces in women of reproductive age. Only about 50 cases of peritoneal disseminated leiomyomatosis have been reported (19). It is difficult to distinguish multiple peritoneal nodules from peritoneal dissemination (20). Peritoneal disseminated leiomyomatosis is initiated or promoted by hormonal factors; the leiomyomas regress after hormonal stimulation is stopped. Many of the reported cases have been associated with pregnancy.
Retroperitoneal Growth
Leiomyomas usually grow into the peritoneal cavity. However, they sometimes demonstrate retroperitoneal growth, usually within the broad ligament. In this situation, the leiomyoma mimics a retroperitoneal tumor by displacing the bladder, rectum, or even descending colon anteriorly (Fig 12). Because of the pressure of the surrounding tissue, the lesion tends to have an irregular rather than rounded configuration. Identification of feeding or draining vessels arising from the myometrium is helpful in distinguishing an intraligamental leiomyoma from a retroperitoneal tumor (21).
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Figure 12. Leiomyoma with extensive intraligamental growth in a 55-year-old woman. Axial fast spin-echo T2-weighted MR image (6,000/86.8) shows anterior displacement of the descending colon (arrowheads) by a mass (arrows). Although the lesion appears to be a retroperitoneal tumor, surgery demonstrated a leiomyoma growing into the retroperitoneum within the broad ligament.
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Parasitic Growth
A pedunculated leiomyoma may lose its connection with the uterus due to torsion and necrosis of the pedicle. The leiomyoma may then become attached to other pelvic structures or the omentum and be supplied by parasitic vessels (Fig 13).
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Figure 13a. Leiomyoma attached to the fallopian tube in a 32-year-old woman. Axial spin-echo T2-weighted (2,000/70) (a) and gadolinium-enhanced T1-weighted (600/20) (b) MR images show a mass (arrows), which demonstrates high signal intensity on the T2-weighted image (a) and heterogeneous enhancement on the gadolinium-enhanced image (b). This myxoid leiomyoma had a blood supply only from the fallopian tube and was considered to be a parasitic growth, although this fact was not clear at MR imaging.
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Abstract
INTRODUCTION
