CASE 13775 Published on 16.08.2016

Ovarian mature cystic teratoma: MR imaging findings

Section

Genital (female) imaging

Case Type

Clinical Cases

Authors

Christina Naka, Athina C. Tsili, Maria I. Argyropoulou

Department of Clinical Radiology,
Medical School,
University of Ioannina,
Ioannina, Greece.

Patient

47 years, female

Categories

Area of Interest Genital / Reproductive system female ; Imaging Technique MR, MR-Diffusion/Perfusion

Procedure Comparative studies ; Special Focus Neoplasia ;

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Clinical History

A 47-year-old woman was referred for an incidentally detected non-cystic left adnexal mass on ultrasound examination. Laboratory analysis, including tumour markers was unremarkable. MRI examination of the pelvis followed.

Imaging Findings

MRI revealed the presence of a unilocular, heterogeneous, sharply-defined mass originating from the left adnexa (Fig. 1). The dimensions of the mass were 77×85×73 mm. A fluid-fluid level and a heterogeneous floating solid part were detected within the lesion. The intracystic nondependent fluid and part of the floating mass showed high signal intensity on both T1 (Fig. 1a) and T2-weighted images (Fig. 1b), approximating that of fat. Suppression of the high-signal intensity of the lesion was observed on fat saturated T1-weighted images (Fig. 1c). On DW images, the same components demonstrated severely restricted diffusion (Fig. 1d). The uterus and the right ovary were normal. No intravenous contrast medium was given.
Despite the lesion’s restricted diffusion, conventional MRI findings, namely hyperintensity on T1-weighted images and signal decrease on fat-saturated T1-weighted sequences were considered diagnostic for mature cystic teratoma.

Discussion

MRI diagnosis was subsequently confirmed on pathology, following cyst excision.
Mature cystic teratoma (MCT, also known as dermoid cyst) is the most common benign ovarian tumour in women less than 45 years of age [3]. MCTs are cystic tumours composed of well-differentiated derivations from at least two of the three embryonic germ cell layers. The gross pathologic appearance is characteristic. These tumours are unilocular in 88% of cases, filled with sebaceous material and lined with squamous epithelium. Hair follicles, skin glands, muscle and other tissues lie within the wall. Furthermore, there is usually a raised protuberance projecting into the cyst cavity known as the Rokitansky nodule, which gives rise to most of the hair and may contain fat, bone and teeth. Fat-fluid levels may also be detected [1-4].
Imaging diagnosis of MCT is usually straightforward on conventional MRI, due to the presence of fat. Specifically, the sebaceous component has very high T1 signal, similar to that of fat and intermediate to high T2 signal. Sequences with frequency-selective fat saturation will suppress the high signal of teratomas, confirming the diagnosis [1-7]. Based on the ESUR guidelines, contrast-enhanced imaging is not recommended for the diagnosis of MCTs. T1 ‘hyperintense’ masses require fat-suppressed T1WI using chemical presaturation to suggest the diagnosis of MCT [8].
The additional diagnostic contribution of DWI in differentiating benign from malignant cystic adnexal lesions remains controversial [9-15]. Low ADC may be seen in many benign cystic adnexal masses, such as MCTs, endometriomas, haemorrhagic functional ovarian cysts and cysts that contain dense mucinous material [9-15]. MCTs exhibit lower ADC compared to other benign or malignant cystic adnexal lesions for two reasons. DWI with EPI sequences usually uses a fat saturation RF pulse, so that the signal intensities of fat are suppressed and measurements of ADC become extremely low. Moreover, the presence of keratinoid substance within the tumour results in restricted diffusion [9-15]. The above characteristics may also create difficulties in the early detection of malignant transformation of MCTs [13].
It is important to be familiar with the DWI characteristics of MCTs to avoid misinterpretation, although these tumours may be accurately diagnosed when DW images are interpreted in conjunction with conventional T1, fat-suppressed T1 and T2-weighted MR images. However, although DWI restriction is not mandatory for the diagnosis of MCT, it can be affirmative. DWI may also add useful differential diagnostic information in patients with fatless MCTs [9, 13-15].

Differential Diagnosis List

Mature cystic ovarian teratoma

Immature teratoma

Endometrioma

Haemorrhagic ovarian cyst

Pedunculated lipoleiomyoma of the uterus

Ovarian serous or mucinous cystadenoma/cystadenocarcinoma

Final Diagnosis

Mature cystic ovarian teratoma

References

[1] Outwater EK, Siegelman ES, Hunt JL (2001) Ovarian Teratomas: Tumor Types and Imaging Characteristics. RadioGraphics 21:475-490 (PMID: 11259710)

[2] Togashi K, Nishimura K, Itoh K, et al (1997) Ovarian cystic teratomas: MR imaging. Radiology 162:669-673 (PMID: 3809479)

[3] Jung SE, Lee JM, Rha SE, Byun JY, Im Jung JI, Hahn ST (2002) CT and MR Imaging of Ovarian Tumors with Emphasis on Differential Diagnosis. RadioGraphics 22:1305-1325 (PMID: 12432104)

[4] Jeong YY, Outwater EK, Kang HK (2000) Imaging Evaluation of Ovarian Masses. RadioGraphics 20:1445-1470 (PMID: 10992033)

[5] Guinet C, Buy JN, Ghossain MA, et al (1993) Fat suppression techniques in MR imaging of mature ovarian teratomas: comparison with CT. Eur J Radiology 17:117-121 (PMID: 8223679)

[6] Imaoka I, Sugimura K, Okizuka H, Iwanari O, KitaoM, Ishida T (1993) Ovarian cystic teratomas: value of chemical fat saturation magnetic resonance imaging. Br J Radiol 66:994-997 (PMID: 8281392)

[7] Stevens SK, Hricak H, Campos Z (1993) Teratomas versus cystic hemorrhagic adnexal lesions: differentiation with proton-selective fat-saturation MR imaging. Radiology 186:481-488 (PMID: 8421755)

[8] Spencer JA, Forstner R, Cunha TM, et al (2010) ESUR guidelines for MR imaging of the sonographically indeterminate adnexal mass: an algorithmic approach. Eur Radiol 20:25-35. (PMID: 20069737)

[9] Namimoto T, Awai K, Nakaura T (2009) Role of diffusion-weighted imaging in the diagnosis of gynecological diseases. Eur Radiol 19:745-760. (PMID: 18839179)

[10] Nakayama T, Yoshimitsu K, Irie H, et al (2005) Diffusion-weighted echo-planar MR imaging and ADC mapping in the differential diagnosis of ovarian cystic masses: usefulness of detecting keratinoid substances in mature cystic teratomas. J Magn Reson Imaging 22:271-278. (PMID: 16028258)

[11] Moteki T, Ishizaka H (2000) Diffusion-weighted EPI of cystic ovarian lesions: evaluation of cystic contents using apparent diffusion coefficients. J Magn Reson Imaging 12:1014-1019. (PMID: 11105044)

[12] Katayama M, Masui T, Kobayashi S, Ito T, Sakahara H, Nozaki A, Kabasawa H (2002) Diffusion-weighted echo planar imaging of ovarian tumors: is it useful to measure apparent diffusion coefficients?. J Comput Assist Tomogr 26:250-256. (PMID: 11884782)

[13] Fujii S, Kakite S, Nishihara K, Kanasaki Y, Harada T, Kigawa J, Kaminou T, Ogawa T (2008) Diagnostic accuracy of diffusion-weighted imaging in differentiating benign from malignant ovarian lesions. J Magn Reson Imaging 28:1149-1156. (PMID: 18972356)

[14] Dhanda S,Thakur M, Kerkar R, Jagmohan P (2014) Diffusion-weighted Imaging of Gynecologic Tumors: Diagnostic Pearls and Potential Pitfalls. RadioGraphics 34:1393-1416. (PMID: 25208287)

[15] Mohaghegh P, Rockall AG (2012) Imaging strategy for early ovarian cancer: characterization of adnexal masses with conventional and advanced imaging techniques. RadioGraphics 32:1751-1773. (PMID: 23065168)

Case information

URL:	https://www.eurorad.org/case/13775
DOI:	10.1594/EURORAD/CASE.13775
ISSN:	1563-4086

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This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Figure 1

MRI examination

Axial T1-weighted image shows a left adnexal mass (arrow) with a fluid-fluid level and a floating solid element (long arrow), the latter corresponding to Rokitansky nodule on histology. Parts of the lesion appear hyperintense.

Axial T2-weighted image depicts heterogeneous left adnexal mass, mainly of high signal intensity. Normal right ovary (arrow) and uterus (long arrow).

Axial fat-suppressed T1-weighted image demonstrates saturation of the hyperintense T1 components (arrow, long arrow) of the lesion, findings compatible with the presence of fat.