DOI: 10.1148/rg.251045060
RadioGraphics 2005;25:21-40
© RSNA, 2005
MR Imaging Findings of Adenomyosis: Correlation with Histopathologic Features and Diagnostic Pitfalls1
Ken Tamai, MD,
Kaori Togashi, MD,
Tsuyoshi Ito, MD,
Nobuko Morisawa, MD,
Toshitaka Fujiwara, MD and
Takashi Koyama, MD
1 From the Department of Radiology, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (K. Tamai, T.I., N.M.); the Departments of Nuclear Medicine and Diagnostic Imaging, Graduate School of Medicine, Kyoto University, Japan (K. Togashi, T.F.); and the Department of Radiology, Kyoto University Hospital, Japan (T.K.). Presented as an education exhibit at the 2003 RSNA Scientific Assembly. Received March 31, 2004; revision requested April 29 and received August 3; accepted August 5. All authors have no financial relationships to disclose. Address correspondence to K. Tamai, Departments of Nuclear Medicine and Diagnostic Imaging, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan (e-mail: tamai@kuhp.kyoto-u.ac.jp).
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Abstract
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Adenomyosis is a nonneoplastic condition, characterized by benign invasion of ectopic endometrium into the myometrium with hyperplasia of adjacent smooth muscle. The common symptoms include dysmenorrhea, menorrhagia, and abnormal uterine bleeding, but these do not allow diagnosis. Therefore, imaging plays an important role because establishment of the correct preoperative diagnosis is critical to avoid unnecessary intervention. Magnetic resonance (MR) imaging is a highly accurate noninvasive modality for diagnosis of adenomyosis, differentiation of adenomyosis from other gynecologic disorders, and planning of appropriate treatment. Although the typical MR imaging findings are well established, adenomyosis actually varies widely in terms of histopathologic features (adenomyosis with sparse glands), growth patterns (polypoid adenomyoma, adenomyotic cyst, and miniature uterus), responses to hormonal activity (tamoxifen, decidual changes), and responses to treatment (gonadotropin-releasing hormone agonist). The MR imaging findings of adenomyosis occasionally mimic those of uterine malignancy or ovarian cancer. Furthermore, malignancy occasionally develops in otherwise benign adenomyosis. Pitfalls in diagnosis of adenomyosis include myometrial contractions, leiomyoma, adenomatoid tumor, metastases, endometrial carcinoma, and endometrial stromal sarcoma. Knowledge of the various appearances of adenomyosis and the possible pitfalls in differential diagnosis help guide the determination of appropriate treatment options.
© RSNA, 2005
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LEARNING OBJECTIVES FOR TEST 2
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After reading this article and taking the test, the reader will be able to:
- Identify the MR imaging features of adenomyosis with usual and unusual appearances.
- Discuss the correlation between the MR imaging findings and histopathologic features of adenomyosis.
- Describe the possible pitfalls in diagnosis of adenomyosis.
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Introduction
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Adenomyosis is a common gynecologic condition that affects menstruating women. Diagnosis based on clinical findings is usually difficult because of the nonspecific nature of the symptoms and the frequent coexistence of other pelvic diseases. Until recently, the diagnosis was established at biopsy or surgery. With the advent of high-resolution imaging techniques, correct diagnosis can be established with imaging modalities (1).
Transabdominal sonography (TAS) or transvaginal sonography (TVS) is commonly used as the initial imaging modality. TAS does not allow reliable diagnosis of adenomyosis or consistent differentiation from leiomyomas because of its limited spatial resolution (2). TVS, which can improve spatial resolution with its higher frequency, is known to be accurate in diagnosing adenomyosis, but it actually has limitations in tissue characterization.
Magnetic resonance (MR) imaging is also an accurate, noninvasive modality for diagnosing adenomyosis and may be more helpful than TVS in distinguishing adenomyosis from a leiomyoma, which is perhaps the most clinically important distinction. Although the typical findings of the lesion are well established, MR imaging findings vary widely, occasionally mimicking uterine malignancy or ovarian cancer. Furthermore, malignancy can develop in otherwise benign adenomyosis. Precise knowledge of histopathologic backgrounds helps identify these unusual appearances and avoid unnecessary intervention.
Specific topics discussed in this article are the definition of adenomyosis and pathologic considerations, clinical information, diagnosis, a wide variety of MR imaging findings of adenomyosis, pseudolesions masquerading as adenomyosis, unusual appearances, differential diagnosis of adenomyosis, and problems related to malignancy.
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Definition and Pathologic Considerations
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Adenomyosis is a nonneoplastic condition, pathologically characterized by benign invasion of ectopic endometrium into the myometrium with adjacent smooth muscle hyperplasia. Although it has been referred to as endometriosis interna, this term recently is no longer used because endometriosis and adenomyosis are different disorders. Because the endometrial-myometrial junction is normally irregular, physiologic penetration of endometrium into the myometrium can be misdiagnosed as adenomyosis. In general, endometrial glands lying deeper than one-fourth of the thickness of the myometrium or deeper than one-half of a low-power field (about 2.5 mm) are defined as adenomyosis (3). However, these criteria actually vary among pathologists. According to differences in diagnostic criteria and the thoroughness of the pathologic examination, the reported prevalence of adenomyosis in hysterectomy specimens varies from 5% to 70% (4).
In gross appearance, the uterus is usually firm, enlarged, and somewhat globular. The cut surface of the thickened myometrium is trabeculated and occasionally contains hemorrhagic foci. At microscopy, the ectopic endometrium may form small or large islands within the myometrium surrounded by myometrial hypertrophy. The ectopic endometrial glands within adenomyosis are generally of the basalis type and do not respond to cyclic ovarian hormones, unlike those of endometriosis. However, unusual responses, such as secretory changes, cyclic hemorrhage, or decidual reactions, may infrequently be observed (5). These issues are discussed later.
A rare pathologic feature is adenomyosis with sparse glands, in which the glandular component is especially sparse. This condition may pathologically simulate a low-grade endometrial stromal sarcoma (LGESS) and cause diagnostic problems for pathologists, because the tumor cells of LGESS usually resemble benign endometrial stromal cells in the proliferative phase with scant cytologic atypia and even rarely have mature endometrial glands (6). Therefore, imaging study is important to make the distinction. These issues are also discussed later. Previously used designations, such as stromal adenomyosis, stromatosis, or stromal endometriosis, are not currently recommended because such designations have been wrongly applied to true endometrial stromal neoplasms in the old literature.
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Clinical Information
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Adenomyosis occurs mainly in premenopausal women, particularly those who are multiparous. The common symptoms include dysmenorrhea, menorrhagia, and abnormal uterine bleeding. However, these symptoms are nonspecific and often seen in other disorders, such as dysfunctional uterine bleeding, leiomyoma, endometriosis, and uterine malignancies. The uterus may be diffusely enlarged, but this finding can also be seen in leiomyoma. Furthermore, patients frequently have associated disorders, most commonly leiomyoma and endometriosis (5).
The etiology of adenomyosis is still under debate. However, tamoxifen, which is a nonsteroidal antiestrogen agent that is widely used for treatment of estrogen-sensitive breast cancer, is known to increase the incidence of adenomyosis in postmenopausal women (7).
Treatment for adenomyosis depends on the patients symptoms, age, and desire for future fertility. The definitive treatment is hysterectomy, but initially less invasive approaches should be tried. If symptomatic relief can be obtained with nonsteroidal anti-inflammatory drugs, or if the patient is perimenopausal with anticipated cessation of ovarian function, conservative therapy is warranted. If adequate relief is not obtained, menstrual-suppression hormonal therapy with danazol (oral or IUD [intrauterine device]) or gonadotropin-releasing hormone (GnRH) agonist, which induces a hypoestrogenic state, should be considered. However, hormonal therapy for adenomyosis is usually less effective than that for endometriosis because of the differences in hormonal responses of the ectopic endometrium, which is of the basalis type in adenomyosis.
Endometrial resection or ablation is considered an alternative to hysterectomy for patients with abnormal uterine bleeding. However, the success rate of this procedure is lower when there is deep adenomyosis (8). Hysterectomy will still be necessary in severe cases of adenomyosis. Uterine artery embolization (UAE), which is emerging as an alternative to hysterectomy for patients with leiomyomas, may also become an alternative for patients with symptomatic adenomyosis (9).
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Diagnosis
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Eliciting a typical history and identifying a diffusely enlarged uterus with a proven absence of pregnancy allows presumptive diagnosis of adenomyosis. However, the rate of preoperative diagnosis based on clinical findings is poor, ranging from 2.6% to 26%, because of the nonspecific nature of the symptoms and the frequent coexistence of other disorders (2). Until recently, the diagnosis was rarely established before surgical exploration.
TAS or TVS is commonly used as the initial imaging modality for patients with clinically suspected adenomyosis. The reported sensitivity and specificity of TAS are 32.5%63% and 95%97%, respectively (10,11). The limited resolution of TAS is insufficient for reproducible detection of subtle sonographic features of adenomyosis (2). Meanwhile, the recent advent of high resolution in TVS has markedly improved the possibility for preoperative diagnosis of adenomyosis. The reported sensitivity and specificity of TVS for diagnosing adenomyosis are 53%89% and 67%98%, respectively (10,12,13). Typical appearances of adenomyosis at TVS include poorly marginated hypoechoic and heterogeneous areas within the myometrium, myometrial cysts, and a globular or enlarged uterus with asymmetry (1,10).
MR imaging is also an accurate, noninvasive modality for diagnosing adenomyosis with a high sensitivity (78%88%) and specificity (67%93%) (10,12,13). This modality might be more helpful than TVS in delineating the location and extent of the lesion and in monitoring the evolution of disease in patients receiving hormonal therapy (1,2). Moreover, MR imaging is useful in distinguishing adenomyosis from a leiomyoma in cases of enlarged uterus, which is perhaps the most clinically important distinction (14). Few studies have compared the accuracy rates of TVS and MR imaging for diagnosing adenomyosis. Some authors reported no significant difference between TVS and MR imaging in the sensitivity (65%89% vs 78%86%) and specificity (89%98% vs 86%93%) (10,13), while others reported that MR imaging was significantly better than TVS (88% vs 53%) (12). In patients with additional lesions like leiomyomas, the sensitivity of TVS was lower than that of MR imaging (10).
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MR Imaging Findings
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Adenomyosis appears as either diffuse or focal thickening of the junctional zone forming an ill-defined area of low signal intensity, occasionally with embedded bright foci on T2-weighted images (Fig 1). Histologically, areas of low signal intensity correspond to smooth muscle hyperplasia, and bright foci on T2-weighted images correspond to islands of ectopic endometrial tissue and cystic dilatation of glands. When menstrual hemorrhage occurs within these ectopic endometrial tissues, signal intensity on T1-weighted images may become high (Fig 2) (1416). Even without hemorrhage or treatment, the appearance of adenomyosis and the amount of bright foci may fluctuate (Fig 3).

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Figure 1a. Adenomyosis in a 48-year-old woman. (a) Sagittal T1-weighted image shows an enlarged uterus with homogeneous signal intensity. (b) Sagittal T2-weighted image shows an ill-defined myometrial lesion of low signal intensity in the anterior myometrium. Innumerable hyperintense foci (arrows) are embedded in the lesion.
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Figure 1b. Adenomyosis in a 48-year-old woman. (a) Sagittal T1-weighted image shows an enlarged uterus with homogeneous signal intensity. (b) Sagittal T2-weighted image shows an ill-defined myometrial lesion of low signal intensity in the anterior myometrium. Innumerable hyperintense foci (arrows) are embedded in the lesion.
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Figure 2a. Adenomyosis with hemorrhagic foci in a 52-year-old woman. (a) Sagittal T1-weighted image shows an enlarged uterus with multiple hyperintense foci in the anterior myometrium (arrows), which represent hemorrhage. (b) Sagittal T2-weighted image shows an ill-defined area of low signal intensity in the anterior myometrium. Hyperintense foci (arrows) are embedded in the lesion. (c) Photograph of the cut surface of the gross specimen shows multiple hemorrhagic cysts within a thickened myometrium. (d) Photomicrograph (original magnification, x40; hematoxylin-eosin [H-E] stain) shows an island of ectopic endometrial tissue that contains blood (arrowheads).
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Figure 2b. Adenomyosis with hemorrhagic foci in a 52-year-old woman. (a) Sagittal T1-weighted image shows an enlarged uterus with multiple hyperintense foci in the anterior myometrium (arrows), which represent hemorrhage. (b) Sagittal T2-weighted image shows an ill-defined area of low signal intensity in the anterior myometrium. Hyperintense foci (arrows) are embedded in the lesion. (c) Photograph of the cut surface of the gross specimen shows multiple hemorrhagic cysts within a thickened myometrium. (d) Photomicrograph (original magnification, x40; hematoxylin-eosin [H-E] stain) shows an island of ectopic endometrial tissue that contains blood (arrowheads).
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Figure 2c. Adenomyosis with hemorrhagic foci in a 52-year-old woman. (a) Sagittal T1-weighted image shows an enlarged uterus with multiple hyperintense foci in the anterior myometrium (arrows), which represent hemorrhage. (b) Sagittal T2-weighted image shows an ill-defined area of low signal intensity in the anterior myometrium. Hyperintense foci (arrows) are embedded in the lesion. (c) Photograph of the cut surface of the gross specimen shows multiple hemorrhagic cysts within a thickened myometrium. (d) Photomicrograph (original magnification, x40; hematoxylin-eosin [H-E] stain) shows an island of ectopic endometrial tissue that contains blood (arrowheads).
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Figure 2d. Adenomyosis with hemorrhagic foci in a 52-year-old woman. (a) Sagittal T1-weighted image shows an enlarged uterus with multiple hyperintense foci in the anterior myometrium (arrows), which represent hemorrhage. (b) Sagittal T2-weighted image shows an ill-defined area of low signal intensity in the anterior myometrium. Hyperintense foci (arrows) are embedded in the lesion. (c) Photograph of the cut surface of the gross specimen shows multiple hemorrhagic cysts within a thickened myometrium. (d) Photomicrograph (original magnification, x40; hematoxylin-eosin [H-E] stain) shows an island of ectopic endometrial tissue that contains blood (arrowheads).
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Figure 3a. Changing appearance of adenomyosis in a 47-year-old woman. (a) Sagittal T2-weighted image obtained on day 16 of the menstrual cycle shows a myometrial mass of high signal intensity protruding into the uterine cavity (arrows). (b) Sagittal T2-weighted image obtained 22 days later (on cycle day 10) shows the typical appearance of adenomyosis. Adenomyosis was confirmed at surgery.
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Figure 3b. Changing appearance of adenomyosis in a 47-year-old woman. (a) Sagittal T2-weighted image obtained on day 16 of the menstrual cycle shows a myometrial mass of high signal intensity protruding into the uterine cavity (arrows). (b) Sagittal T2-weighted image obtained 22 days later (on cycle day 10) shows the typical appearance of adenomyosis. Adenomyosis was confirmed at surgery.
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With the advent of high-resolution imaging techniques, these bright foci are being detected with increasing frequency, one report finding them in more than 50% of patients. Such findings may manifest as myometrial cysts, myometrial nodules, linear striations, pseudowidening of the endometrium (Fig 4), and poor definition of the endometrial junction (1) and are discussed further in the sections regarding differential diagnosis and problems related to malignancy. MR imaging findings of adenomyosis will be modified by the use of gonadotropin-releasing hormone (GnRH) agonist. In patients responding well to GnRH agonist therapy, demarcated changes of the lesion can be observed, which may resemble a leiomyoma (17). Knowledge of the patients medical history can prevent misdiagnosis.

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Figure 4a. Pseudowidening of the endometrium in a 49-year-old woman. (a) Sagittal T2-weighted image shows an ill-defined area of high signal intensity along the posterior myometrium (arrows). The lesion simulates widening of the endometrium but actually represents benign, extensive invasion of ectopic endometrium into the myometrium. (b) Photograph of the histopathologic slide shows ectopic endometrial tissue extensively extending into the myometrium (arrows), an appearance that corresponds to the endometrial pseudowidening on the T2-weighted image. Arrowheads = eutopic endometrium.
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Figure 4b. Pseudowidening of the endometrium in a 49-year-old woman. (a) Sagittal T2-weighted image shows an ill-defined area of high signal intensity along the posterior myometrium (arrows). The lesion simulates widening of the endometrium but actually represents benign, extensive invasion of ectopic endometrium into the myometrium. (b) Photograph of the histopathologic slide shows ectopic endometrial tissue extensively extending into the myometrium (arrows), an appearance that corresponds to the endometrial pseudowidening on the T2-weighted image. Arrowheads = eutopic endometrium.
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Pseudolesions Masquerading as Adenomyosis
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Focal thickening of the junctional zone can easily lead to a diagnosis of adenomyosis, whereas diffuse thickening should be differentiated from physiologic thickening. The presence of bright foci on T2- or T1-weighted images supports the diagnosis of adenomyosis. In general, a maximal junctional zone thickness of more than 12 mm is highly predictive of the presence of adenomyosis, while a thickness of less than 8 mm usually allows exclusion of the disease (2,18). However, in our experience, the uterus during menstruation (especially cycle days 1 and 2) may demonstrate marked thickening of the junctional zone to more than 12 mm (Fig 5). The diagnosis of adenomyosis should be made with care, possibly avoiding the menstrual phase.

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Figure 5. Thickening of the junctional zone during the menstrual phase in a 31-year-old woman. Sagittal T2-weighted image obtained on cycle day 1 shows marked thickening of the junctional zone (arrows), which may closely simulate adenomyosis. The low-signal-intensity band in the endometrium (arrowheads) represents menstrual blood.
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Another pseudolesion that may masquerade as adenomyosis is a myometrial contraction. Sustained myometrial contraction is the focal and sporadic bulging of the myometrium into the uterine cavity. Blood is squeezed out from the contracted area, and water content is reduced because of the reduced blood volume. As a result, the contracted area exhibits ill-defined or sharply marginated areas of low signal intensity on T2-weighted images (19). Contractions can be differentiated from true myometrial disease on sequential studies by their transient nature, but this is not always easy on single series (Fig 6). Previously, the detection rate of pseudolesions due to uterine contraction was about 9% with use of the static fast spin-echo technique (19). But recently, a high detection rate of up to 72%75% has been reported with use of the multiphase single-shot fast spin-echo technique (20).

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Figure 6a. Myometrial contraction in a healthy 30-year-old woman, who underwent MR imaging during a study that evaluated myometrial contractions during the menstrual phase. The half-Fourier acquisition single-shot turbo spin-echo sequence was used to obtain T2-weighted images. (a) Sagittal image obtained on cycle day 1 shows a focal area of low signal intensity in the anterior myometrium (arrows), a finding that closely simulates focal adenomyosis. (b) Sagittal image obtained on cycle day 3 shows a normal uterus with a thin and distinct junctional zone.
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Figure 6b. Myometrial contraction in a healthy 30-year-old woman, who underwent MR imaging during a study that evaluated myometrial contractions during the menstrual phase. The half-Fourier acquisition single-shot turbo spin-echo sequence was used to obtain T2-weighted images. (a) Sagittal image obtained on cycle day 1 shows a focal area of low signal intensity in the anterior myometrium (arrows), a finding that closely simulates focal adenomyosis. (b) Sagittal image obtained on cycle day 3 shows a normal uterus with a thin and distinct junctional zone.
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Unusual Appearances
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Unusual Growth Patterns
Adenomyoma.
Adenomyoma is defined as a localized, circumscribed form of adenomyosis. The lesion typically manifests as a polypoid mass protruding into the cavity. Less commonly, it may manifest as a myometrial mass (Fig 7) or as a subserosal mass (21). Recognition of this pathologic entity is important because it may be surgically treated with polypectomy or myomectomy, unlike an ordinary form of adenomyosis. However, adenomyoma is frequently misdiagnosed as other tumors, not only at MR imaging but also at pathologic examination. At MR imaging, myometrial adenomyoma typically exhibits low signal intensity on T2-weighted images (1,15), an appearance indistinguishable from that of the more common leiomyoma. When the lesion is accompanied by small foci of high signal intensity representing ectopic endometrial tissue, adenomyoma can be considered in the differential diagnosis.

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Figure 7a. Intramyometrial adenomyoma in a 21-year-old woman. (a, b) Axial (a) and sagittal (b) T2-weighted images show an ill-defined, low-signal-intensity mass with an embedded hyperintense cyst in the posterior myometrium (arrows). (c) Sagittal T1-weighted image shows that the cyst within the mass (arrows) has high signal intensity, which represents hemorrhage. Myomectomy was performed, and adenomyosis was pathologically confirmed.
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Figure 7b. Intramyometrial adenomyoma in a 21-year-old woman. (a, b) Axial (a) and sagittal (b) T2-weighted images show an ill-defined, low-signal-intensity mass with an embedded hyperintense cyst in the posterior myometrium (arrows). (c) Sagittal T1-weighted image shows that the cyst within the mass (arrows) has high signal intensity, which represents hemorrhage. Myomectomy was performed, and adenomyosis was pathologically confirmed.
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Figure 7c. Intramyometrial adenomyoma in a 21-year-old woman. (a, b) Axial (a) and sagittal (b) T2-weighted images show an ill-defined, low-signal-intensity mass with an embedded hyperintense cyst in the posterior myometrium (arrows). (c) Sagittal T1-weighted image shows that the cyst within the mass (arrows) has high signal intensity, which represents hemorrhage. Myomectomy was performed, and adenomyosis was pathologically confirmed.
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Polypoid adenomyoma (adenomyomatous polyp) and atypical polypoid adenomyoma: Adenomyoma manifesting as a polypoid mass protruding into the endometrial cavity is called polypoid adenomyoma or adenomyomatous polyp and accounts for about 2% of all endometrial polyps. It typically occurs in premenopausal women and manifests as abnormal genital bleeding. It arises most frequently in the lower uterine segment or endocervix and appears as a pedunculated or sessile polypoid mass (22). At MR imaging, the lesion appears as a hypointense polypoid mass with hyperintense foci on T2-weighted images (Fig 8) (23).

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Figure 8a. Tamoxifen-induced adenomyoma in a 56-year-old woman. The patient underwent breast-conserving therapy for breast carcinoma 2 years earlier and was treated with tamoxifen. (a) Sagittal T2-weighted image shows a polypoid mass of heterogeneous high signal intensity in the endometrial cavity (arrows). (b) Sagittal contrast-enhanced T1-weighted image shows that the mass (arrows) enhances as well as the myometrium. (c) Photomicrograph (original magnification, x20; H-E stain) shows endometrial tissue surrounded by hyperplastic smooth muscle.
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Figure 8b. Tamoxifen-induced adenomyoma in a 56-year-old woman. The patient underwent breast-conserving therapy for breast carcinoma 2 years earlier and was treated with tamoxifen. (a) Sagittal T2-weighted image shows a polypoid mass of heterogeneous high signal intensity in the endometrial cavity (arrows). (b) Sagittal contrast-enhanced T1-weighted image shows that the mass (arrows) enhances as well as the myometrium. (c) Photomicrograph (original magnification, x20; H-E stain) shows endometrial tissue surrounded by hyperplastic smooth muscle.
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Figure 8c. Tamoxifen-induced adenomyoma in a 56-year-old woman. The patient underwent breast-conserving therapy for breast carcinoma 2 years earlier and was treated with tamoxifen. (a) Sagittal T2-weighted image shows a polypoid mass of heterogeneous high signal intensity in the endometrial cavity (arrows). (b) Sagittal contrast-enhanced T1-weighted image shows that the mass (arrows) enhances as well as the myometrium. (c) Photomicrograph (original magnification, x20; H-E stain) shows endometrial tissue surrounded by hyperplastic smooth muscle.
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Atypical polypoid adenomyoma is a variant of polypoid adenomyoma and is microscopically characterized by architectural and cytologic atypia. The reported MR imaging finding is a hypointense polypoid mass with bright foci on T2-weighted images (Fig 9) (23). In the evaluation of histologic samples, especially those obtained with dilation and curettage, atypical polypoid adenomyoma may be misdiagnosed as endometrial carcinoma invading the myometrium. Preoperative information provided by MR imaging, based on the signal intensity of the lesion, can be the clue to making a distinction.

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Figure 9a. Atypical polypoid adenomyoma in a 42-year-old woman. (a) Sagittal T1-weighted image shows a pedunculated polypoid mass projecting into the cervical canal (arrows). The mass has intermediate signal intensity and contains a large hyperintense cyst (arrowheads), which represents hemorrhage. (b) Sagittal T2-weighted image shows that the polypoid mass has slightly high signal intensity (arrows); the embedded cyst is hyperintense (arrowheads). (c) Photograph of the histopathologic slide shows the polypoid mass and the relatively large but deflated cyst (arrowheads), which correlates with the hemorrhagic cyst seen on the MR images.
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Figure 9b. Atypical polypoid adenomyoma in a 42-year-old woman. (a) Sagittal T1-weighted image shows a pedunculated polypoid mass projecting into the cervical canal (arrows). The mass has intermediate signal intensity and contains a large hyperintense cyst (arrowheads), which represents hemorrhage. (b) Sagittal T2-weighted image shows that the polypoid mass has slightly high signal intensity (arrows); the embedded cyst is hyperintense (arrowheads). (c) Photograph of the histopathologic slide shows the polypoid mass and the relatively large but deflated cyst (arrowheads), which correlates with the hemorrhagic cyst seen on the MR images.
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Figure 9c. Atypical polypoid adenomyoma in a 42-year-old woman. (a) Sagittal T1-weighted image shows a pedunculated polypoid mass projecting into the cervical canal (arrows). The mass has intermediate signal intensity and contains a large hyperintense cyst (arrowheads), which represents hemorrhage. (b) Sagittal T2-weighted image shows that the polypoid mass has slightly high signal intensity (arrows); the embedded cyst is hyperintense (arrowheads). (c) Photograph of the histopathologic slide shows the polypoid mass and the relatively large but deflated cyst (arrowheads), which correlates with the hemorrhagic cyst seen on the MR images.
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Adenomyotic Cyst.
An adenomyotic cyst is an extremely rare variation of adenomyosis caused by extensive menstrual bleeding into the ectopic endometrium. The lesion consists of a large hemorrhagic cyst, which is partly or entirely surrounded by a solid wall. The lesion can be entirely within the myometrium, submucosal, or subserosal and frequently is associated with symptoms of menorrhagia and dysmenorrhea. Rupture can rarely occur.
At MR imaging, fluid content exhibits high signal intensity on T1-weighted images and the surrounding solid wall exhibits distinct low signal intensity on T2-weighted images (Fig 10) (24,25). Occasionally, the solid wall may develop two zones consisting of an inner zone of low signal intensity that resembles a junctional zone and a relatively bright outer myometrium, and this is called miniature uterus (Fig 11). Microscopically, endometrial glands are observed along the cyst wall, which is composed of myometrial tissue. However, on pathologic studies, endometrial glands are often atrophic or missing on small tissue samples and hyaline degeneration is sometimes observed within the lesion. In this situation, an adenomyotic cyst is easily misdiagnosed as a leiomyoma from pathologic studies because the existence of smooth muscle cells and hyaline degeneration is considered almost pathognomonic for a leiomyoma. However, ectopic endometrial tissue should not be recognized with leiomyoma. In this regard, MR imaging can be crucial for a correct diagnosis (24).

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Figure 10a. Subserosal adenomyotic cyst in a 46-year-old woman. (a) Sagittal T1-weighted image shows a cystic mass posterior to the uterus (U). The lesion consists of a hyperintense cyst, on top of which is curvilinear tissue of intermediate signal intensity (arrows). (b) Sagittal T2-weighted image shows that the curvilinear tissue is hypointense (arrows). (c) Sagittal contrast-enhanced T1-weighted image shows the curvilinear tissue (arrows) enhancing as well as the myometrium. A pedicle containing enlarged vessels (arrowheads) connects the lesion to the uterus, indicating the uterine origin of the mass. Thus, the preoperative diagnosis was degenerated subserosal leiomyoma. (d) Photograph of the cut surface shows the hemorrhagic cystic mass and the curvilinear solid tissue (arrows). The initial pathologic diagnosis was leiomyoma because the lesion consisted of smooth muscle cells and hyaline degeneration. (e) Photomicrograph (original magnification, x40; H-E stain) shows endometrial tissue containing hemorrhage (arrow) and hemosiderin (arrowhead) lining the cyst wall.
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Figure 10b. Subserosal adenomyotic cyst in a 46-year-old woman. (a) Sagittal T1-weighted image shows a cystic mass posterior to the uterus (U). The lesion consists of a hyperintense cyst, on top of which is curvilinear tissue of intermediate signal intensity (arrows). (b) Sagittal T2-weighted image shows that the curvilinear tissue is hypointense (arrows). (c) Sagittal contrast-enhanced T1-weighted image shows the curvilinear tissue (arrows) enhancing as well as the myometrium. A pedicle containing enlarged vessels (arrowheads) connects the lesion to the uterus, indicating the uterine origin of the mass. Thus, the preoperative diagnosis was degenerated subserosal leiomyoma. (d) Photograph of the cut surface shows the hemorrhagic cystic mass and the curvilinear solid tissue (arrows). The initial pathologic diagnosis was leiomyoma because the lesion consisted of smooth muscle cells and hyaline degeneration. (e) Photomicrograph (original magnification, x40; H-E stain) shows endometrial tissue containing hemorrhage (arrow) and hemosiderin (arrowhead) lining the cyst wall.
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Figure 10c. Subserosal adenomyotic cyst in a 46-year-old woman. (a) Sagittal T1-weighted image shows a cystic mass posterior to the uterus (U). The lesion consists of a hyperintense cyst, on top of which is curvilinear tissue of intermediate signal intensity (arrows). (b) Sagittal T2-weighted image shows that the curvilinear tissue is hypointense (arrows). (c) Sagittal contrast-enhanced T1-weighted image shows the curvilinear tissue (arrows) enhancing as well as the myometrium. A pedicle containing enlarged vessels (arrowheads) connects the lesion to the uterus, indicating the uterine origin of the mass. Thus, the preoperative diagnosis was degenerated subserosal leiomyoma. (d) Photograph of the cut surface shows the hemorrhagic cystic mass and the curvilinear solid tissue (arrows). The initial pathologic diagnosis was leiomyoma because the lesion consisted of smooth muscle cells and hyaline degeneration. (e) Photomicrograph (original magnification, x40; H-E stain) shows endometrial tissue containing hemorrhage (arrow) and hemosiderin (arrowhead) lining the cyst wall.
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Figure 10d. Subserosal adenomyotic cyst in a 46-year-old woman. (a) Sagittal T1-weighted image shows a cystic mass posterior to the uterus (U). The lesion consists of a hyperintense cyst, on top of which is curvilinear tissue of intermediate signal intensity (arrows). (b) Sagittal T2-weighted image shows that the curvilinear tissue is hypointense (arrows). (c) Sagittal contrast-enhanced T1-weighted image shows the curvilinear tissue (arrows) enhancing as well as the myometrium. A pedicle containing enlarged vessels (arrowheads) connects the lesion to the uterus, indicating the uterine origin of the mass. Thus, the preoperative diagnosis was degenerated subserosal leiomyoma. (d) Photograph of the cut surface shows the hemorrhagic cystic mass and the curvilinear solid tissue (arrows). The initial pathologic diagnosis was leiomyoma because the lesion consisted of smooth muscle cells and hyaline degeneration. (e) Photomicrograph (original magnification, x40; H-E stain) shows endometrial tissue containing hemorrhage (arrow) and hemosiderin (arrowhead) lining the cyst wall.
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Figure 10e. Subserosal adenomyotic cyst in a 46-year-old woman. (a) Sagittal T1-weighted image shows a cystic mass posterior to the uterus (U). The lesion consists of a hyperintense cyst, on top of which is curvilinear tissue of intermediate signal intensity (arrows). (b) Sagittal T2-weighted image shows that the curvilinear tissue is hypointense (arrows). (c) Sagittal contrast-enhanced T1-weighted image shows the curvilinear tissue (arrows) enhancing as well as the myometrium. A pedicle containing enlarged vessels (arrowheads) connects the lesion to the uterus, indicating the uterine origin of the mass. Thus, the preoperative diagnosis was degenerated subserosal leiomyoma. (d) Photograph of the cut surface shows the hemorrhagic cystic mass and the curvilinear solid tissue (arrows). The initial pathologic diagnosis was leiomyoma because the lesion consisted of smooth muscle cells and hyaline degeneration. (e) Photomicrograph (original magnification, x40; H-E stain) shows endometrial tissue containing hemorrhage (arrow) and hemosiderin (arrowhead) lining the cyst wall.
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Figure 11a. Submucosal adenomyotic cyst in a 37-year-old woman. (a) Sagittal T2-weighted image obtained 3 years earlier shows typical adenomyosis. (b) Sagittal T1-weighted image shows a polypoid mass in the endometrial cavity (arrows). The hyperintense area in the mass is hemorrhage. (c) Sagittal T2-weighted image shows the well-defined cystic mass (arrows). Its thick wall has inner low and outer high signal intensity (miniature uterus). The uterus is enlarged due to adenomyosis. (d) Sagittal contrast-enhanced T1-weighted image shows marked enhancement of the wall (arrows). (e) Photograph of the cut surface shows the uterus-like mass (arrows). (f) Photomicrograph (original magnification, x40; H-E stain) shows the cyst (*) surrounded by layers of endometrial tissue and smooth muscle.
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Figure 11b. Submucosal adenomyotic cyst in a 37-year-old woman. (a) Sagittal T2-weighted image obtained 3 years earlier shows typical adenomyosis. (b) Sagittal T1-weighted image shows a polypoid mass in the endometrial cavity (arrows). The hyperintense area in the mass is hemorrhage. (c) Sagittal T2-weighted image shows the well-defined cystic mass (arrows). Its thick wall has inner low and outer high signal intensity (miniature uterus). The uterus is enlarged due to adenomyosis. (d) Sagittal contrast-enhanced T1-weighted image shows marked enhancement of the wall (arrows). (e) Photograph of the cut surface shows the uterus-like mass (arrows). (f) Photomicrograph (original magnification, x40; H-E stain) shows the cyst (*) surrounded by layers of endometrial tissue and smooth muscle.
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Figure 11c. Submucosal adenomyotic cyst in a 37-year-old woman. (a) Sagittal T2-weighted image obtained 3 years earlier shows typical adenomyosis. (b) Sagittal T1-weighted image shows a polypoid mass in the endometrial cavity (arrows). The hyperintense area in the mass is hemorrhage. (c) Sagittal T2-weighted image shows the well-defined cystic mass (arrows). Its thick wall has inner low and outer high signal intensity (miniature uterus). The uterus is enlarged due to adenomyosis. (d) Sagittal contrast-enhanced T1-weighted image shows marked enhancement of the wall (arrows). (e) Photograph of the cut surface shows the uterus-like mass (arrows). (f) Photomicrograph (original magnification, x40; H-E stain) shows the cyst (*) surrounded by layers of endometrial tissue and smooth muscle.
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Figure 11d. Submucosal adenomyotic cyst in a 37-year-old woman. (a) Sagittal T2-weighted image obtained 3 years earlier shows typical adenomyosis. (b) Sagittal T1-weighted image shows a polypoid mass in the endometrial cavity (arrows). The hyperintense area in the mass is hemorrhage. (c) Sagittal T2-weighted image shows the well-defined cystic mass (arrows). Its thick wall has inner low and outer high signal intensity (miniature uterus). The uterus is enlarged due to adenomyosis. (d) Sagittal contrast-enhanced T1-weighted image shows marked enhancement of the wall (arrows). (e) Photograph of the cut surface shows the uterus-like mass (arrows). (f) Photomicrograph (original magnification, x40; H-E stain) shows the cyst (*) surrounded by layers of endometrial tissue and smooth muscle.
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Figure 11e. Submucosal adenomyotic cyst in a 37-year-old woman. (a) Sagittal T2-weighted image obtained 3 years earlier shows typical adenomyosis. (b) Sagittal T1-weighted image shows a polypoid mass in the endometrial cavity (arrows). The hyperintense area in the mass is hemorrhage. (c) Sagittal T2-weighted image shows the well-defined cystic mass (arrows). Its thick wall has inner low and outer high signal intensity (miniature uterus). The uterus is enlarged due to adenomyosis. (d) Sagittal contrast-enhanced T1-weighted image shows marked enhancement of the wall (arrows). (e) Photograph of the cut surface shows the uterus-like mass (arrows). (f) Photomicrograph (original magnification, x40; H-E stain) shows the cyst (*) surrounded by layers of endometrial tissue and smooth muscle.
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Figure 11f. Submucosal adenomyotic cyst in a 37-year-old woman. (a) Sagittal T2-weighted image obtained 3 years earlier shows typical adenomyosis. (b) Sagittal T1-weighted image shows a polypoid mass in the endometrial cavity (arrows). The hyperintense area in the mass is hemorrhage. (c) Sagittal T2-weighted image shows the well-defined cystic mass (arrows). Its thick wall has inner low and outer high signal intensity (miniature uterus). The uterus is enlarged due to adenomyosis. (d) Sagittal contrast-enhanced T1-weighted image shows marked enhancement of the wall (arrows). (e) Photograph of the cut surface shows the uterus-like mass (arrows). (f) Photomicrograph (original magnification, x40; H-E stain) shows the cyst (*) surrounded by layers of endometrial tissue and smooth muscle.
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Unusual Responses to Hormonal Stimuli
Although the ectopic endometrium of adenomyosis seldom responds to cyclic ovarian hormones, in some cases, secretory changes may be seen, and decidual reaction may be encountered if the patient is pregnant (Fig 12) (5). Even without pregnancy, the appearance of adenomyosis may occasionally fluctuate, probably reflecting hormonal responses. The lesion may appear as a mass of heterogeneous high signal intensity, masquerading as a malignant uterine neoplasm on one occasion and then showing an otherwise typical appearance of adenomyosis on another (Fig 3). Follow-up MR imaging may be helpful to identify any change in signal intensity and to avoid misdiagnosis.

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Figure 12a. Decidual changes of adenomyosis in a 23-year-old woman with a hydatidiform mole. (a) Sagittal T2-weighted image shows an ill-defined lesion of heterogeneous high signal intensity in the posterior myometrium (arrows) in addition to a lesion in the uterine cavity (arrowheads). (b) Sagittal T2-weighted image obtained after suction and curettage shows that the lesion in the posterior myometrium is reduced in volume and signal intensity and now has the typical appearance of adenomyosis (arrows). The lesion in the uterine cavity was confirmed to be a hydatidiform mole. This case seems to represent decidual changes of adenomyosis because the serum level of human chorionic gonadotropin was highly elevated when the lesion demonstrated prominent high signal intensity in a.
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Figure 12b. Decidual changes of adenomyosis in a 23-year-old woman with a hydatidiform mole. (a) Sagittal T2-weighted image shows an ill-defined lesion of heterogeneous high signal intensity in the posterior myometrium (arrows) in addition to a lesion in the uterine cavity (arrowheads). (b) Sagittal T2-weighted image obtained after suction and curettage shows that the lesion in the posterior myometrium is reduced in volume and signal intensity and now has the typical appearance of adenomyosis (arrows). The lesion in the uterine cavity was confirmed to be a hydatidiform mole. This case seems to represent decidual changes of adenomyosis because the serum level of human chorionic gonadotropin was highly elevated when the lesion demonstrated prominent high signal intensity in a.
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Differential Diagnosis of Adenomyosis
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Distinction from Typical Adenomyosis
Leiomyoma.
Leiomyoma is by far the most commonly encountered lesion that clinically resembles adenomyosis. A correct preoperative diagnosis is critical when uterine conservation is desired or myomectomy is scheduled, since leiomyoma can be treated with myomectomy, whereas adenomyosis requires hysterectomy (14). In contrast to leiomyoma, adenomyosis manifests with a poorly defined border, minimal mass effect, an elliptical rather than round configuration, and absence of dilated vessels at the margin of the lesion (Fig 13) (1,14).