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GYNAECOLOGY AND OBSTETRICS Table of Contents   
Year : 2005  |  Volume : 15  |  Issue : 2  |  Page : 271-276
Varied appearances & signal characteristics of leiomyomas on MR imaging


Diwanchand Aggarwal Imaging & Research Centre, 10-B, K.G. Marg, New Delhi-110001, India

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Keywords: Leiomyomas, MRI

How to cite this article:
Aggarwal B K, Panwar S, Rajan S, Aggarwal A, Ahlawat K. Varied appearances & signal characteristics of leiomyomas on MR imaging. Indian J Radiol Imaging 2005;15:271-6

How to cite this URL:
Aggarwal B K, Panwar S, Rajan S, Aggarwal A, Ahlawat K. Varied appearances & signal characteristics of leiomyomas on MR imaging. Indian J Radiol Imaging [serial online] 2005 [cited 2019 Sep 21];15:271-6. Available from: http://www.ijri.org/text.asp?2005/15/2/271/28820

   Introduction Top


Since its inception, the technical quality and range of application of pelvic MRI has steadily increased. MR imaging has emerged as an important imaging modality for evaluation of the female pelvis because of its excellent soft tissue contrast, tissue specificity, lack of ionizing radiation and non-invasive nature [1]. Newer technical innovations of multicoil and fast spin echo sequences have increased the signal to noise ratio & shortened acquisition time. This essay describes the usefulness of MRI in demonstrating location, relationships and characterization of various forms of degeneration in uterine leiomyomas.


   Technique Top


MR imaging was performed on a 1.5T super-conducting magnet (Symphony, Siemens AG, Erlangen, Germany) using a dedicated phased array body coil. Routine axial T1-weighted, axial, sagittal and coronal T2-weighted images were obtained [Table - 1]. Additional fat saturated T1-weighted and T2-weighted scans were taken, where necessary.


   Leiomyomas Top


Leiomyomas are the commonest benign uterine tumors occurring in 20-30% of pre-menopausal women [2]. Typical uncomplicated fibroids are well circumscribed, sharply marginated, rounded homogenous masses displaying intermediate signal intensity on T1-weighted images (T1WI), often indistinguishable from the adjacent myometrium. However, optimal contrast is achieved on T2-weighted images (T2WI), where they are hypointense relative to the myometrium [3],[4]. The typical MR imaging feature of leiomyoma-distinct low signal intensity on T2-weighted images-is due to extensive hyalinization [5],[6].

Ninety percent of these are located in the corpus uteri in the Intramural (when bulk of the tumor was within the myometrium) [Figure - 1], subserosal (when the epicenter of the lesion is beyond the outer uterine wall), or submucosal (when they protrude into the endometrial cavity) locations [Figure - 2] [2]. Five percent each are located in the cervical [Figure - 3] & broad ligament regions respectively [Figure - 4][Figure - 5]. Prolapse [Figure - 6] and partial detachment of the myomas have also been seen.


   Degenerative Leiomyomas Top


To understand the wide spectrum of MR imaging findings, unusual appearances of leiomyomas 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) [6], 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 [5].

A variety of degenerations alter the signal intensity of leiomyomas that demonstrate a characteristic speckled or heterogeneous pattern, exhibiting areas of high signal intensity interlacing within low intensity masses [3]. The alteration in signal intensity on T2WI depends on the degree of cellularity, hyalinization & hemorrhage [4],[7]. Hyaline degeneration is the commonest form producing a characteristic "speckled" pattern [Figure - 7].

Edema may change into various degrees of collagen deposition and cystic degeneration. Cystic degeneration may be considered an extreme sequel of edema and is observed in about 4% of leiomyomas. Large or small cystic spaces develop in the edematous, acellular center. 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 [Figure - 8]. Myxoid material demonstrates high signal intensity on the T2-weighted image, low signal intensity on the T1-weighted image. Viable tissue has relatively low signal intensity on the T2-weighted image [5]

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 [3], and is also associated with use of oral contraceptives. 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. 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 [5]. Hemorrhage in a myoma may have variable MR appearances depending on imaging sequence used & stage of evolution of the bleed [4] [Figure - 9].

Although calcification has no specific MR appearance, lack of signal within masses that does not change with different TR & TE parameters is highly suggestive of calcification [2]. We have found this most apparent on fat saturated T1 weighted scans. 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 [Figure - 9]. This type of calcification appears to represent thrombosed veins from past red degeneration [5].

Lipoleiomyoma / fatty degeneration is easy to diagnose, being hyperintense on T1WI with a characteristic signal drop-off on fat suppressed sequence [Figure - 10]. Larger myomas having speckled & whorled appearance containing interspersed mucinous & myxomatous material are often difficult to specifically distinguish on MR [Figure - 11], as is the rare sarcomatous change [2],[3],[4]. Hemorrhage and necrosis (other than red degeneration) are not common but may be observed in leiomyomas.


   Differential Diagnosis Top


Leiomyomas & adenomyosis having the same clinical presentation & frequent concurrent occurrence often pose pre-op diagnostic dilemmas, especially focal adenomyosis (Adenomyoma). The former is amenable to conservative (myomectomy) & the latter to radical surgery (hysterectomy). MR imaging is sensitive in reflecting the pathological difference between the two [1],[3]. The less vascularity with lack of edema & the ectopic migration of the endometrium into the myometrium causing the adenomyotic foci to inter-digitate are responsible for its low signal, ill-defined margins & contiguity with the junctional zone. Myomas, in turn, are well defined due to the halo of compressed adjacent myometrium forming a pseudo-capsule [Figure - 12]. Also leiomyomas are round in comparison to adenomyomas which tend to be oval along the long axis of the uterus [1],[3].

Often it is impossible to distinguish a solid adnexal tumor lying in close proximity to the uterus from a pedunculated subserosal fibroid on sonography alone, especially if both the ovaries are not identified. One such example being ovarian fibroma which displays similar signal intensity as myoma on MR [8]. Non-visualisation of the ovary or visualization of a remnant follicle at its periphery, and change in position of the mass in relation to the uterus on pre-post void imaging gives the diagnosis [Figure - 13].

Leiomyomas are often associated with numerous obstetric complications including decreased fertility, the mechanism of which is not known. Myomectomy has resulted in improved fertility in some of the cases. Although ultrasound is the initial screening modality, sonographic limitations include marked uterine distortion, multiplicity of lesions, operator dependence & tumor size. MR outperforms ultrasound & hysterosalpingograms in the same [9].

Contrast enhanced T1WI do not improve the assessment of fibroids except when in unusual location or when unenhanced T2WI are of inferior quality [10]. They may also have a role in pre-embolisation evaluation to control excessive menorrhagia.


   Conclusion Top


MRI is an accurate means available for precise determination of location, relationships and detection of degeneration within these benign tumors of the uterus. The precise type of degeneration can also often be characterized by MR, providing pertinent information before any surgical intervention is contemplated.

 
   References Top

1.Mark AS, Hricak H : Adenomyosis & leiomyomas : Differential diagnosis by means of MRI. Radiology 163: 527,1987.  Back to cited text no. 1    
2.Hricak H, Tscholakoff D, Heinrichs L, et al : Uterine leiomyomas correlation by Magnetic Resonance Imaging : clinical symptoms & histopathology. Radiology 158: 385, 1986.  Back to cited text no. 2    
3.Togashi K, Ozaka H, Konishi I, et al : Enlarged uterus : Differentiation between adenomyosis & leiomyomas with MRI. Radiology 171: 531,1989.  Back to cited text no. 3    
4.Hamlin DJ, Pettersson H, Fitzsimmons J, et al : MR imaging of uterine Leiomyomas & their complications. J Comput Assist Tomography 9:902, 1985.  Back to cited text no. 4    
5.Ueda H, Togashi K, Konishi I , et al. Unusual Appearances of Uterine Leiomyomas: MR Imaging Findings and Their Histopathologic Backgrounds Radiographics. 1999;19:S131-S145.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]
6.Rosai J. Ackerman's surgical pathology 8th ed. St Louis, Mo: Mosby-Year Book, 1996; 1429-1433.  Back to cited text no. 6    
7.Weinreb JC, Barkoff ND, Megibow A, et al : The value of MR imaging in distinguishing leiomyomas from other solid pelvic masses when sonography is indeterminate. Am J of Roentgenology 154: 295, 1990.  Back to cited text no. 7    
8.Chopra S, Ahlawat K, Aggarwal B, et al: Demonstration of an Ovarian Fibroma by ultrasound and MRI: A Case Report. Asian Oceanian Journal of Radiology. Vol. 7 No 2; 84-87, 2002.  Back to cited text no. 8    
9.Dudiak CM, Turner DA, Patal SK, et al : Uterine leiomyomas in the infertile patient : Pre-operative localization with MRI versus US & HSG. Radiology 167: 627, 1988.  Back to cited text no. 9    
10.Hricak H, Finck S, Honda G, et al : MR imaging in the evaluation of benign uterine masses : value of gadopentetate dimeglumine enhanced T1W images. Am J of Roentgenology 158: 1043, 1992.  Back to cited text no. 10    

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Correspondence Address:
B K Aggarwal
10-B Kasturba Gandhi Marg, New Delhi 110 001
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.28820

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    Figures

[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9], [Figure - 10], [Figure - 11], [Figure - 12], [Figure - 13]

    Tables

[Table - 1]

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    Introduction
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    Leiomyomas
    Degenerative Lei...
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