Ovarian germ cell tumor MRI

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sahar Memar Montazerin, M.D.[2] Monalisa Dmello, M.B,B.S., M.D. [3]

Abdominal/pelvic MRI may be helpful in the diagnosis of ovarian germ cell tumors. Findings on MRI suggestive of ovarian germ cell tumors include masses with a cystic and solid component and may contain fat, calcification, fat–fluid level, Tuft\Hairs, Palm tree-like protrusion, and Dermoid nipples-like elements (Rokitansky nodules). The majority of ovarian germ cell tumors have a solid and cystic appearance with areas of hemorrhage and necrosis. The predominance of cystic or solid component differs for each tumor.

Mature teratoma

Pelvic MRI is sensitive in the diagnosis of mature teratoma. Findings on MRI suggestive of of mature teratoma include:^[1]

• Fat
  • Fat may be misdiagnosed with hemorrhage in the hemorrhagic cysts and it should be differentiated from that in three following ways:
    • Chemical-shift artifact in the frequency-encoding direction
    • Gradient-echo imaging with an echo time when water and fat are in the opposite state
    • Sequences with frequency-selective fat saturation
• Calcification
• Fat–fluid level
• Tuft\Hairs
• Palm tree-like protrusion
• Dermoid nipple-like elements (Rokitansky nodules)

Mondermal teratoma

• Struma ovarii:
  • MR imaging findings may be more characteristics for the diagnosis and include:^[2]
    • Absence of fat
    • Cystic spaces with both high and low signal intensity on T1 and T2 images
    • Thick, gelatinous colloid of struma may be associated with a low-intensity signal on both T1 and T2 images.
    • A multilocular mass with variable degree of signal intensity in T1 and T2 images in the locular spaces.
• Carcinoid tumor:
  • Absence of fat
  • It should be distinguished from other solid malignancies.

Immature ovarian teratoma

• Foci of fat interspaced within solid the solid mass^[3]
• Fatty liquid may be observed in cystic component
• Calcifications are small, irregular, and scattered through the tumor

Dysgerminomas

• Lobulated solid mass^[3]
• Interspaced fibrovascular septa
  • Septa, when edematous, are hyperintense on T2 images
• Low signal intensity compared to muscle on T1 image
• Isointense or slightly hyperintense on T2 image
• It can also mimic the appearance of epithelial ovarian neoplasms:
  • Multilobular mass with cysts, papillary projections and irregular septations

Yolk sac tumor

• The bright dot sign (enhancing foci in the wall or solid component) is the common finding, although it is not the pathognomonic finding for the yolk sac tumor.^[3]
• Capsular tear is another common finding which is not the pathognomonic finding for the yolk sac tumor.
• Areas of hemorrhage with high signal intensity on T1 images can also be observed.

Embryonal tumor

• The tumor is large, predominantly solid and unilateral with areas of necrosis and hemorrhage.^[4]
• There may be cystic areas that contains mucoid material.

Choriocarcinoma

• Highly vascularized solid mass^[4]
• Vascular component produces signals in T2 images.

Mixed germ cell tumors

• There is no specific imaging criteria for these tumors.^[4]
• Imaging may vary according to the content of the tumors.
• Finding associated with yolk sac tumor and dysgerminoma are more common.

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