Struma ovarii: appearance on MR images

A large benign struma ovarii with atypical imaging findings

Struma ovarii is a mature ovarian teratoma characterized by the predominant presence of thyroid-tissue components. Typically, struma ovarii presents as relatively small masses (<10 cm) that often appear as multilocular cystic tumors with solid components. Herein, we report the unique case of a 44-year-old female with a large tumor including a solid mass. The solid components of the tumor comprised typical thyroid tissues with multiple small cystic structures containing colloid-like material. Given the rarity of struma ovarii, atypical imaging features can sometimes be misleading. This article highlights the unusual magnetic resonance imaging characteristics of a large struma ovarii, with a specific focus on the presence of solid components.

A Case of Solid-Appearing Struma Ovarii: Pitfall in the Assessment Using Ovarian-Adnexal Reporting and Data System Magnetic Resonance Imaging Score

Struma ovarii is a monodermal teratoma characterized by the presence of >50% thyroid tissue. It is mostly benign; therefore, preoperative diagnosis is important. It usually manifests as a multilocular cystic mass but rarely as a predominantly solid mass. On magnetic resonance imaging (MRI), solid-appearing struma ovarii showed early signal intensity enhancement on dynamic gadolinium-enhanced T1-weighted images, which histopathologically indicates the presence of thyroid tissue with abundant blood vessels. The Ovarian-Adnexal Reporting and Data System (O-RADS) MRI score is a validated classification worldwide for characterizing adnexal lesions. Based on the morphology, signal intensity, and enhancement of any solid tissue on the MRI, the scoring system can be used to classify adnexal lesions into five categories from score one (no adnexal mass) to score five (high risk of malignancy). An adnexal solid mass with a higher signal intensity than that of the myometrium 30-40 seconds after gadolinium (Gd) injection on non-dynamic contrast-enhanced (non-DCE) MRI was assigned a score of 5 (high risk of malignancy).  We present a case of solid-appearing struma ovarii with a higher signal intensity than that of the myometrium 30 seconds after Gd injection on non-DCE MRI, and it was classified as score five preoperatively. Therefore, a total abdominal hysterectomy with bilateral salpingo-oophorectomy was performed despite the presence of a benign ovarian mass. When an adnexal mass with a higher signal intensity than that of the myometrium 30-40 seconds after Gd injection on non-DCE MRI is encountered, struma ovarii should be included in the differential diagnosis, despite the O-RADS MRI score of five and management of the situation should be discussed.

Current state of management of struma ovarii and preoperative imaging features: A retrospective case series study of 18 patients at a single institution

AIM

Even though 95% of struma ovarii are benign, it is often overtreated because of the difficulty to distinguish it from malignancy. In this study, our aim was to evaluate the current state of the preoperative diagnosis and the selection of the surgical procedure, and to improve preoperative diagnostic accuracy by retrospectively reviewing imaging findings.

METHODS

We retrospectively reviewed the clinical course and imaging characteristics of 18 patients who were diagnosed postoperatively with struma ovarii, pathologically, at our institution between 2015 and 2021.

RESULTS

The preoperative diagnoses included benign ovarian tumor in eight cases, borderline in four cases, and malignant in six cases. None of the cases were diagnosed as struma ovarii preoperatively. Of the seven patients who had confirmed a desire for future childbearing, four patients were suspected for borderline or malignant tumor preoperatively, and underwent abdominal adnexectomy. In patients without a desire for childbearing, laparoscopic surgery was performed in only 45% of the patients whose preoperative diagnosis was benign. On magnetic resonance imaging (MRI), 54% of the cases showed enhanced solid components, which is characteristic of malignant tumors, but diffusion restriction was observed in only 11%. On computed tomography (CT), 78% of the cases showed a high attenuation lesion reflecting thyroid tissue.

CONCLUSIONS

Struma ovarii is difficult to distinguish from malignancy preoperatively, making the choice of surgical approach complicated. A comprehensive evaluation of diffusion-weighted MRI and CT findings may improve the accuracy of preoperative diagnosis of struma ovarii.

Management of malignant struma ovarii: is aggressive therapy justified? Case report and literature review

Background

Struma ovarii (SO) is a rare ovarian teratoma containing predominantly thyroid tissue. In rare situations SO may develop malignancy. Most cases of malignant struma ovarii (MSO) are diagnosed after surgical removal, based on histopathological examination. There are still controversies regarding the extent of surgery and postoperative management in MSO, due to its unpredictable behavior, possible risk of metastasis and relatively high rate of recurrence.

Case Presentation

We present the case of a patient diagnosed with a right ovarian cyst discovered incidentally during routine ultrasound examination. Its rapid growth and pelvic MRI raised the suspicion of a neoplastic process. She underwent total hysterectomy and bilateral adnexectomy. The anatomopathological diagnosis was MSO with follicular variant of papillary thyroid carcinoma. Prophylactic total thyroidectomy was performed, followed by radioactive iodine ablation (RAI), and suppressive therapy with levothyroxine. At 1 year follow-up, the patient was disease free.

Conclusions

Even if latest literature reports consider that completion of local surgery with total thyroidectomy and RAI might be too aggressive in cases of MSO without extraovarian extension, in our case it was decided to follow the protocol for primary thyroid carcinoma, in order to reduce the recurrence risk.

Pearls and Potential Pitfalls for Correct Diagnosis of Ovarian Cystadenofibroma in MRI: A Pictorial Essay

Ovarian cystadenofibroma is a benign ovarian tumor that is characterized by a consistent percentage of masses, which remain indeterminate in ultrasonography and require magnetic resonance (MR) investigation; they may mimic borderline or malignant lesions. Three main morphologic patterns, resembling different ovarian neoplasms, can be identified in cystadenofibromas: multilocular solid lesions, unilocular cystic lesions with parietal thickening, and purely cystic masses. However, a cystoadenofibroma has typical features, such as T2-weighted hypointensity associated with no restrictions in diffusion-weighted imaging (the so-called "dark-dark appearance") and progressive post-contrast enhancement (type I perfusion curve). The purpose of this study was to review the features of ovarian cystadenofibromas in MR imaging and to suggest pearls and pitfalls regarding their correct diagnosis.

Ovarian teratomas: clinical features, imaging findings and management

Ovarian teratomas are the most common type of germ cell tumors. There are three major subtypes of ovarian teratomas including mature, immature, and monodermal teratomas. Ultrasound, computed tomography and magnetic resonance imaging can demonstrate specific imaging findings for mature teratoma. Imaging features of immature and monodermal teratomas are less specific, but a combination of clinical features and imaging findings can help in the diagnosis. Imaging is also very helpful in guiding management. In this article, we review the epidemiology, histopathology, clinical presentation, imaging features and management of ovarian teratomas.

Struma ovarii: two case reports of a rare teratoma of the ovary

Struma ovarii is an extremely rare type of ovarian teratoma distinguished by the unusual presence of thyroid tissue. It is usually a benign condition; however, malignant transformation is sometimes detected. The diagnosis relies on histopathological examination and is infrequently made on routine investigations. We report two cases of struma ovarii: one benign and the other malignant. The first case involved a 27-year-old woman who underwent a right ovarian cystectomy for an incidental ultrasonographic finding of a solid right adnexal mass. The diagnosis of a benign struma was made after histopathological study. The second case involved a 68-year-old woman who underwent a right salpingo-oophorectomy for a right ovarian bulky mass and the histopathological diagnosis was consistent with that of a malignant struma. We examine the challenges involved in the diagnosis and management of this rare entity.

[Benign struma ovarii: Report of 7 cases and review of the literature]

OBJECTIVE

Struma ovarii is a monodermal teratoma composed of thyroid tissue, representing 0.85 to 1.3% of ovarian tumors. The objective of the present study is to report a continuous series of struma ovarii, with a comprehensive analysis of the literature.

METHODS

A retrospective study in the gynecological surgery department of Hôpital Femme-Mère-Enfant (Hospices Civils de Lyon, Lyon, France) assessed a continuous series of struma ovarii from the Lyon East Pathology Center database. Clinical and biological, imaging and pathological aspects were analyzed and the various forms of treatment described.

RESULTS

We identified 7 patients with struma ovarii from March 2008 to April 2015. Mean patient age was 49.7 years (28-70years). Three patients had a history of thyroid disease. CA-125 was elevated (51IU/mL) in only 1 patient. MRI and ultrasound imaging did not enable diagnosis of struma ovarii, which depended on pathologic examination. Conservative surgery for cystectomy or oophorectomy was performed for patients wishing to become pregnant (71%); nonconservative hysterectomy was performed in postmenopausal women (29%).

CONCLUSIONS

Struma ovarii is a rare, often asymptomatic condition in which diagnosis is difficult. Few series are described in the literature. Here we propose a management model for struma ovarii. Revision surgery and adjuvant therapy is indicated in case of malignant struma ovarii.

Struma ovarii: role of imaging?

As clinical features in struma ovarii patients in the absence of thyrotoxicosis are generally non-specific and resemble ovarian malignancy, preoperative radiological diagnosis becomes all the more relevant in order to avoid ovarian cancer type surgery (including bilateral salpingo-oophorectomy, hysterectomy, omentectomy and occasionally appendectomy) for this usually benign and rare ovarian mass. As struma ovarii is an uncommon entity, it is all the more important to perform state-of-the-art magnetic resonance (MR) imaging, including high-resolution imaging and diffusion-weighted imaging. The goal of this review paper is to give an update of the key findings of both benign and malignant struma ovarii and to present an unusual case of a purely cystic ovarian struma. Key Points • Clinical features in struma ovarii are generally non-specific and resemble ovarian malignancy.• Pre-operative radiological diagnosis is important to avoid ovarian cancer type surgery (bilateral salpingo-oophorectomy, hysterectomy, omentectomy and occasionally appendectomy).• State-of-the-art MR imaging might help to characterise this unusual ovarian mass.• Struma ovarii can occasionally present as a purely cystic lesion.• However, the role of imaging to identify struma ovarii preoperatively remains limited.

Value of dynamic contrast-enhanced MRI for tissue characterization of ovarian teratomas: correlation with histopathology

AIM

To analyse the value of double contrast-enhanced (DCE) magnetic resonance imaging (MRI) in addition to conventional MRI to characterize ovarian teratomas subtypes with histological correlation.

MATERIALS AND METHODS

From January 2005 to December 2008, 38 women undergoing MRI and subsequent resection of ovarian teratomas were identified [40 mature cystic teratomas (MCT), two struma ovarii, three immature teratomas]. MRI images were analysed blindly by two radiologists according to morphological and vascular abnormalities. An experienced histopathologist reviewed all slides to determine the presence and histological composition of Rokitansky protuberances.

RESULTS

Thirty-one MCT (77%) had at least one small, regular Rokitansky protuberance presenting at an acute angle with the cyst wall. Ten out of 31 MCT did not display any enhancement on contrast-enhanced MRI related to sebaceous glands, adipose lobules, keratin, and pilosebaceous adnexa at histology. Three different time-intensity curve (TIC), types 1, 2, and 3, were related to presence of smooth muscular cells and fibrous, neuroglial, or thyroid tissue, respectively, found at histology of MCT. Type 3 TIC was also present in one struma ovarii and two immature teratomas.

CONCLUSION

TIC types are related to the specific content of the solid tissue of ovarian teratomas but cannot be used to differentiate benign and malignant ovarian teratomas.

CT and MR features of struma ovarii

OBJECTIVE

The purpose of this study is to investigate radiologic findings of struma ovarii, and to correlate both CT and MR findings.

MATERIALS AND METHODS

MR images of 26 cases were retrospectively reviewed. Post-contrast enhanced T1-weighted images were available in 17 patients. CT images, including seven non-contrast and eleven post-contrast studies, were available for review in 13 cases.

RESULTS

All 26 tumors appeared as well-defined cystic tumors with solid components, which were multilobulated surfaces in 19 and smooth surfaces in seven. Twenty-four was multicystic, whereas two were unilocular. The solid components were recognized as thickened septi or walls in 23 and a mass in three tumors. On T2-weighted images, loculi of prominent low intensity were recognized in 16 tumors. On T1-weighted images, the punctuate foci of high intensity were recognized in 24 tumors in or adjacent to the solid components. Ascites was present in only one lesion. In six of seven cases with non-contrast CT images, high attenuation areas were recognized. In five of these six tumors, high attenuation areas corresponded to the areas of prominent low intensity and the solid components on T2-weighted images. In seven cases with CT, curvilinear calcifications were recognized in the solid components.

CONCLUSION

Struma ovarii typically presents as a lobulated multicystic lesion with solid components. The tumors frequently include loculi of low intensity on T2-weighted images and punctuate foci of high intensity on T1-weighted images. On CT, high attenuation areas and calcifications in the solid components are common findings.

Struma ovarii with papillary thyroid carcinoma

Struma ovarii is an uncommon condition, in which thyroid tissue is the predominant or exclusive element in an ovarian teratoma. Thyroid tissue may demonstrate the same spectrum of pathological features as in the normal thyroid including benign and malignant changes. We present a case of papillary thyroid carcinoma arising in a struma ovarii of the left ovary in a 21-year-old female.

Struma ovarii: CT findings

BACKGROUND

The purpose of this study was to evaluate computed tomographic findings of struma ovarii.

METHODS

Computed tomography (CT) scans of 13 pathologically proven struma ovarii were retrospectively reviewed by two radiologists in consensus. Scans were evaluated for the laterality, size, mass configuration, margins, internal architecture, presence of intracystic high attenuation lesions on precontrast scans, and cyst wall enhancement.

RESULTS

The mean size of the tumors was 11.4 cm (range 4.7-21.0 cm). Mainly cystic (n = 8, 61.5%) or cystic (n = 5, 38.5%) appearance was common to all the tumors. All tumors were unilateral and had smooth margins. The most common internal architecture in the tumors was multicystic architecture (n = 11, 84.6%). Eleven tumors (84.6%) showed a high attenuation lesion in the cyst portion of the mass on precontrast scans and the attenuation ranged from 92.2 to 120.5 Hounsfield units (HU) (mean, 106.8 +/- 8.8 HU). The cyst wall showed no (n = 7, 53.8%), moderate (n = 5, 38.5%), or marked (n = 1, 7.7%) enhancement after administration of contrast medium.

CONCLUSIONS

On CT scans, struma ovarii appeared most often as a smooth marginated multicystic mass with a high attenuation lesion on precontrast scans and no or moderate cyst wall enhancement.

Imaging of gynecological disease (4): clinical and ultrasound characteristics of struma ovarii

OBJECTIVES

To describe the clinical history and ultrasound findings in women with struma ovarii.

METHODS

Women with a histological diagnosis of struma ovarii who had undergone preoperative ultrasound examination were identified from the databases of five ultrasound centers. The tumors were characterized on the basis of ultrasound images, ultrasound reports and research protocols (when applicable) using the terms and definitions of the International Ovarian Tumor Analysis (IOTA) group. In addition, four authors reviewed all ultrasound images and described them using pattern recognition.

RESULTS

Of 31 patients identified, 16 had pure struma ovarii (one malignant), whereas in 15 patients the struma ovarii were 'impure', constituting the major part of a dermoid cyst (all benign, bilateral in one case). Median age was 40 (range, 18-80) years and 22 (71%) patients were of fertile age. Thirteen patients (42%) were asymptomatic, nine (29%) presented with pain, six (19%) with bloating, two (6%) with irregular bleeding and one (3%) with thyreotoxicosis. Most pure struma ovarii (11/16 cases, 69%) contained solid components, but cystic components were always present. The color content at Doppler examination varied from none to abundant. Four patients had ascites. Using pattern recognition the most specific feature of pure struma ovarii was the 'struma pearl', i.e. a smooth roundish solid area, similar, but not identical, to the 'round white ball' seen in dermoid cysts. 'Struma pearls' were present in six cases of pure struma ovarii. Most (10/16, 63%) cases of impure struma ovarii manifested ultrasound features compatible with a dermoid cyst, but six manifested ultrasound features similar to those of pure struma ovarii, 'struma pearls' being seen in three of these.

CONCLUSIONS

The sonographic features of struma ovarii vary. Struma ovarii may be suspected when a 'struma pearl' is seen. Whether 'struma pearls' are indeed a specific ultrasonographic feature of struma ovarii needs to be determined in a prospective study.

Imaging findings of complications and unusual manifestations of ovarian teratomas

Ovarian teratomas can be associated with various complications and demonstrate a wide spectrum of clinical and imaging features. The complications include torsion (16% of ovarian teratomas), rupture (1%-4%), malignant transformation (1%-2%), infection (1%), and autoimmune hemolytic anemia (<1%). These complications require different therapeutic strategies; therefore, timely and accurate diagnosis of these complications is important for optimal patient treatment. In cases of complicated ovarian teratomas, the clinical manifestations provide only limited information and often overlap with those of other diseases. Furthermore, ovarian teratomas may have unusual clinical and imaging manifestations, thereby leading to misdiagnosis. These unusual manifestations include immature teratomas, monodermal teratomas (struma ovarii), combination tumors and collision tumors containing teratomas, and mature cystic teratomas without demonstrable fat or with pure fatty components. To provide adequate treatment and prevent misdiagnosis, it is necessary to be familiar with the imaging findings of both the complications and the unusual manifestations of ovarian teratomas.

MR findings of ovarian tumors with hormonal activity, with emphasis on tumors other than sex cord-stromal tumors

Sex cord-stromal tumors including granulosa cell tumor, thecoma, Sertoli stromal cell tumor and steroid cell tumor are noted for their hormonal activity. However, there are many kinds of ovarian tumors other than sex cord-stromal tumors and tumor-like conditions with endocrine manifestations. Cross-sectional imaging, especially MR, can provide precise features of ovarian tumors and uterine morphological change even in a clinically latent excess of estrogen. In this article, we demonstrate typical imaging findings of ovarian tumors with hormonal activity. We also shortly explain the mechanism of the virilization and hyperestrogenism caused by ovarian tumors and tumor-like conditions.

Goitre ovarien: une forme particulière de tératome de l'ovaire

Struma ovarii, a rare form of ovarian tumor, represents less than 3% of ovarian teratomas. The peak frequency occurs during the fifth decade of life. Diagnosis is usually a surprise of pelvic ultrasound or histological analysis. Surgery is the main mode of treatment and prognosis is excellent. Struma ovarii can be associated with thyroid biology abnormalities, or exceptionally become malignant, and thus managed as a thyroid cancer.

MR imaging findings of ovarian cystadenofibroma and cystadenocarcinofibroma: clues for the differential diagnosis

Objective

We wanted to assess the MR imaging findings of ovarian cystadenofibroma and cystadenocarcinofibroma, and we wanted to find clues for making the differential diagnosis between them.

Materials and Methods

The MR images of 12 pathologically proven cystadenofibromas and two cystadenocarcinofibromas were reviewed, with a focus on the internal architecture, signal intensity and enhancement.

Results

All the tumors appeared as multilocular cysts, except for a single unilocular cystic mass and a single solid mass. The previously reported characteristic MR findings of cystadenofibroma (a multilocular cystic mass with a T2-dark-signal-intensity solid component containing small cystic locules) were found in only 43% of the tumors (6/14). Diffuse or partial thickening of the cyst wall with T2-dark signal intensity without a definite solid component was as common as the previous reported findings (6/14). Two cystadenocarcinofibromas showed more prominent solid portions with higher T2-signal intensities and stronger enhancement than did the cystadenofibromas.

Conclusion

Diffuse or partial thickening of the cyst wall with dark-signal-intensity in multilocular cystic masses may suggest ovarian cystadenofibroma, and this type of appearance may be as common as the previously reported characteristic appearance. A prominent solid component with a higher T2-signal intensity and strong enhancement are the typical findings of cystadenocarcinofibroma.

Ovarian cancer: the clinical role of US, CT, and MRI

This article presents an overview of ovarian cancer, which addresses the clinical roles of imaging studies, including US, CT, and MR imaging in the course of diagnosis and treatment of this important disease. US is the modality of choice in the evaluation of patients with suspected adnexal masses. Although its accuracy is not sufficient to avert surgery, morphological analysis of adnexal masses with US helps narrow the differential diagnosis, determining the degree of suspicion for malignancy, usually in concert with a serum CA-125 level. Combined morphological and vascular imaging obtained by US appear to further improve the preoperative assessment of adnexal masses. For uncertain or problematic cases, MR imaging helps to distinguish benign from malignant, with an overall accuracy for the diagnosis of malignancy of 93%. The accuracy of MR imaging in the confident diagnosis of mature cystic teratoma, endometrial cysts, and leiomayomas is very high. CT is not indicated for differential diagnosis of adnexal masses because of poor soft tissue discrimination, except for fatty tissue and for calcification, and the disadvantages of irradiation. In the staging of ovarian cancer, CT, US, and MR imaging all have a similarly high accuracy. Although it is difficult to suggest a simple algorithm for evaluating the state of women with adnexal masses, the correct preoperative diagnosis and staging of ovarian cancer with the use of any of these imaging studies will lead to an appropriate referral to a specialist in gynecologic oncology and offer a significant survival advantage for patients with ovarian cancer.

Malignant struma ovarii mimic clear cell carcinoma

INTRODUCTION

Struma ovarii are quite unusual lesions that represent less than 3% of all teratomas and its malignant transformation is very uncommon. The clinical manifestations are characteristic of pelvic tumor and the hormonal metabolism is not usually modified. Radiography, employing ultrasound procedures, is the most commonly used pre-surgical detection method but only histological examination makes the diagnosis. The malignance recognition by pathological study not always is easy; in this sense, it requires an exhaustive sampling of the lesion, being specially carefully in some aspects related with malignant transformation such as extending beyond the capsula and involving peripheral tissues. A thyroidal differentiation must be confirmed by immunohistochemical study and other local processes with similar histology should be ruled out. Given the exceptional character of malignant forms, there does not appear to be unanimous agreement on a standard therapy with a somewhat uncertain prognosis.

CASE REPORT

We show a case of a 22-year-old patient with an ovarian tumor that was discovered by ultrasound examination and surgically removed. The histologic study revealed struma ovarii with malignant transformation towards follicular carcinoma and unlike previously published cases, had a prevalence of clear cells. The patient was submitted to a second surgical staging intervention, with conservative surgery and follow-up controls being considered given that was a young woman with a desire to have children. Laparoscopy was employed as the best method capable to facilitate shorter convalescence.

OUTCOME

Clinical and analytical controls, measuring thyroglobulin levels, has been satisfactory up to the present.

Struma ovarii coexisting with mucinous cystadenoma detected by radioactive iodine

The authors describe a case of struma ovarii coexisting with mucinous cystadenoma. Ultrasonography and magnetic resonance imaging showed a multilocular cystic mass with a solid component. The ovarian tumor demonstrated uptake of I-123 sodium iodide, allowing a preoperative diagnosis of struma ovarii. In women with an unexplained increase in thyroid function and low I-123 uptake in the cervical thyroid gland, scintigraphy of the pelvis should be considered.

Malignant struma ovarii: a case report of laparoscopic management

BACKGROUND

Struma ovarii is a rare disease. Malignant transformation is even rarer. Data about its management are lacking. We describe the first reported case of a malignant struma ovarii treated and staged by laparoscopy.

CASE

A 49-year-old patient was operated by laparoscopy for a right ovarian teratoma. The patient did not show symptoms of hyperthyroidism. The ovarian teratoma was removed in a plastic bag and definitive histology showed foci of papillary adenocarcinoma in a struma ovarii. The patient was then staged by laparoscopic surgery undergoing left adnexectomy, multiple peritoneal and omental biopsies, and common iliac and paracaval lymph node sampling. Hysterectomy was not performed. The postoperative course was uneventful and the patient was released on the second day. Thyroglobulin level was monitored and the patient is free of disease after more than 1 year.

CONCLUSION

The preoperative diagnosis of malignant struma ovarii is difficult. Even with cautious evaluation of the patient, some risk of wrong diagnosis is possible. This is why a meticulous technique of laparoscopic surgery in removing the ovary is important. Laparoscopic staging may also intervene in very limited cases; the expertise to perform open staging of the patient is necessary but the postoperative course is fast.

Cystic Ovarian Lesions in SSFP Diffusion Imaging

PURPOSE

MR assessments of ovarian cystic lesions are usually based on morphological features, signal intensities and enhancement with contrast media. This study was performed to evaluate the usefulness of the steady-state free precession (SSFP) diffusion imaging of cystic ovarian lesions for analyzing cystic contents.

MATERIALS AND METHODS

Sixty-one ovarian cystic lesions in 37 patients were examined. The diffusion-related coefficient (DRC) and the ratio of the relative apparent diffusion coefficient of the lesion to that of subcutaneous fat tissue (rADC(L)/rADC(F)) were calculated from SSFP diffusion images.

RESULTS

The DRCs and the rADC(L)/rADC(F) ratios in endometrial cysts and in the fatty parts of dermoid cysts were significantly lower than in other cystic tumors.

CONCLUSION

SSFP diffusion imaging can be included in clinical practice to analyze ovarian cystic lesions within a short scan time; the DRC and the rADC(L)/rADC(F) ratio are useful for evaluating cystic contents.

Magnetic resonance imaging of the ovary

Magnetic resonance imaging (MRI) of the pelvis can characterize a wide variety of ovarian lesions. We discuss MRI strategies for identification and characterization of ovarian neoplasms and correlate MRI findings with lesion gross pathological and histopathological structure.

Ovarian teratomas: tumor types and imaging characteristics

Ovarian teratomas include mature cystic teratomas (dermoid cysts), immature teratomas, and monodermal teratomas (eg, struma ovarii, carcinoid tumors, neural tumors). Most mature cystic teratomas can be diagnosed at ultrasonography (US) but may have a variety of appearances, characterized by echogenic sebaceous material and calcification. At computed tomography (CT), fat attenuation within a cyst is diagnostic. At magnetic resonance (MR) imaging, the sebaceous component is specifically identified with fat-saturation techniques. The US appearances of immature teratoma are nonspecific, although the tumors are typically heterogeneous, partially solid lesions, usually with scattered calcifications. At CT and MR imaging, immature teratomas characteristically have a large, irregular solid component containing coarse calcifications. Small foci of fat help identify these tumors. The US features of struma ovarii are also nonspecific, but a heterogeneous, predominantly solid mass may be seen. On T1- and T2-weighted images, the cystic spaces demonstrate both high and low signal intensity. Familiarity with the US, CT, and MR imaging features of ovarian teratomas can aid in differentiation and diagnosis.

Cystic struma ovarii: imaging findings

We report three cases of cystic struma ovarii not associated with any solid component. One case was a thin-walled unilocular mass, and the other two cases were multilocular cystic masses. An area of signal void on T2-weighted images and intermediate intensity on T1-weighted images was noted in the two multilocular cases. Preoperative diagnosis was difficult in each case, but struma ovarii should be included in differential diagnoses even in the case of a completely cystic ovarian mass.

MR findings of struma ovarii

This study was performed to characterize MR findings of struma ovarii. In 10 patients, T1- and fast spin echo T2-weighted MR images were obtained in the axial, coronal, and sagittal planes using 1.5 T MR units, and they were retrospectively evaluated for the site, size, components, signal intensity, and contrast enhancement.MR images showed a unilateral complex mass with a multilobulated surface and thickened septa, corresponding pathologically to thyroid follicles and the stroma. Cystic portions had variable signal intensities on T1- and T2-weighted images. The contents of cystic components showing low signal intensities both on T1- and T2-weighted images were viscid gelatinous materials (n=4). Solid portions were relatively well-enhanced. In conclusion, struma ovarii has some characteristic MR appearance of a multilobulated complex mass with thickened septa, multiple cysts of variable signal intensities, and enhancing solid components.