Epidemiology
A rare highly aggressive malignant tumour with trophoblastic differentiation. Serum BHCG is elevated. Presentations include pelvic mass symptoms, amenorrhea, isosexual pseudo-precocity in prepubertal girls and bleeding from metastatic deposits.4
Two types: non-gestational occuring in prepubertal girls and postmenopausal women and gestational choriocarcinoma occuring during reproductive years requiring a recent intra/extrauterine pregnancy.
Incidence of non-gestational choriocarcinoma is 2.1-3.4% of all OMGCT.5 It metastases haematogously and via lymphatics. At presentation, often liver metastases and local pelvic invasion. Leading cause of death is brain metastases occurring in 10-20%.5
· MR Imaging findings
Best diagnostic morphological clue, a large unilateral hypervascular solid adnexal mass with central haemorrhage, necrosis and avid peripheral contrast enhancement.
Table 2. MR characteristics of choriocarcinomas5
T1 |
T2 |
T1 + contrast +FatSat |
Predominately low signal
-High signal areas suggests haemorrhage
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-Mixed signal intensity
-Low signal represents solid component
-High signal represents cystic areas within a peripheral low signal solid component
-High signal central areas represent necrosis/haemorrhage
Invasion of adjacent organs, pelvic side wall and liver metastases may be seen at presentation.
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-Avid enhancement within peripheral solid component
-Peritoneal thickening and deposits best seen on delayed sequences
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Fig. 1: T1 axial shows a homogenuous isointense lesion with flecks of air centrally.
Fig. 2: T2 axial shows central cystic necrotic areas (high signal) with a solid periphery.
Fig. 3: T1 FS axial shows hypervascular lesion with central necrosis and avid peripheral enhancement consistent with a choriocarcinoma.
Fig. 4: T2 axial shows tumour invasion into the adjacent sigmoid colon
Fig. 5: T2 sagittal shows tumour invasion into the adjacent sigmoid colon.
Fig. 6: CT performed at initial presentation shows a liver metastasis.
Table 3: Differential Diagnosis for a hypervascular ovarian mass5
-Ectopic pregnancy- adnexal mass, empty uterus, and elevated bhcg
-Other malignant germ cell tumours
-Dysgerminoma-Large solid mass containing multiple fibrovascular septa +/- calcification.
-Yolk sac stroma- prominent intratumoral vessels and peripheral enhancement. elevated AFP
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Normal beta HCG:
-Sclerosing stromal tumour- Low signal nodules, high signal stroma with thin low T2 peripheral rim. Early peripheral post contrast enhancement with centripedal progression and delayed central enhancement.
-Tubo-ovarian abscess- inflammatory markers, fever, vaginal discharge. Tubular cystic lesions with rim enhancement.
-Massive ovarian oedema- Peripherally placed ovarian follicles within oedematous stroma.
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· Take home message:
Consider in the differential diagnosis for a hypervascular adnexal mass with central necrosis/haemorrhage and mutiple cystic cavities in the solid component. Obtain Beta-HCG levels.
Epidemiology
Incidence is 1-2% of all ovarian neoplasms however it is the most common malignant germ cell tumour with an incidence of 32-37%.2,6,7Seventy five percent occur in adolescence and early adulthood.7Increased incidence in 46XY patients with complete gonadal dysgenesis.2
Dysgerminoma is the ovarian counterpart to testicular seminoma. A pure dysgerminoma does not secrete hormones. Serum LDH and alkaline phosphatase are often elevated with only 5% secreting BHCG. Common presentations include pain and urinary/constipation symptoms related to mass effect.
Characteristically unilateral solid well-encapsulated lobulated large mass presenting with mean diameter of 15cm.6 Nodal metastases are more common than peritoneal metastases(seen in epithelial ovarian cancers). Five year survival rates are excellent at 95% for early stage and 65% for advanced stage using FIGO staging system.
Table 4. MR characteristics of Dysgerminomas 6
T1 |
T2 |
T1 + contrast +Fat Sat |
-Predominately solid hypointense mass relative to adjacent muscle.
-Septa are difficult to appreciate on T1WI
-Internal haemorrhage can be seen – high T1 signal
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-Mass is isointense /slightly hyperintense to muscle
-The septa are usually hypointense/ isointense to muscle
-May be hyperintense when oedematous
-Necrotic areas demonstrate high signal intensity |
-Soft tissue components demonstrate relatively homogeneous enhancement
Fibrovascular septae between lobules demonstrate marked enhancement
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· MR Imaging findings
Fig. 7: T2 sagittal shows a large solid lobulated lesion with intervening oedematous central fibrovascular septae (high signal) consistent with a dysgerminoma.
Fig. 8: T2 coronal shows a large solid lobulated lesion with intervening oedematous central fibrovascular septae (high signal) consistent with a dysgerminoma.
Fig. 9: T1 FS post contrast axial shows a large solid lobulated lesion with homogenuous enhancement and intervening low signal fibrovascular septae in keeping with a dysgerminoma
Fig. 10: T1 FS post contrast sagittal image shows homogenuous enhancement and intervening low signal fibrovascular septae within the solid lobulated in keeping with a dysgerminoma
Fig. 11: CT coronal shows retroperitoneal lymphadenopathy consistent with nodal metastases.
Table 5: Differential Diagnosis for a predominately solid mass6
-Serous and mucinous epithelial ovarian tumours-more complex, cystic multiloculated mass.
-Teratoma-complex mass with cystic and solid components containing fat and calcifications.
-Sex cord stromal tumour-typically solid mass with tumour medicated hormonal effects
-Ovarian metastasis-mostly solid +/- cystic components with the clinical presentation related to the primary disease.
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Take Home message
Consider when there is a large solid unilateral ovarian mass with intervening fibrovascular septae in a young female.
· Epidemiology
Rare with an incidence of less than 1% of all malignant ovarian tumours, usually occurring in the first two decades of life8 and responsible for 30% of ovarian cancer deaths.9
Composed of tissue from the 3 germ cell layers: ectoderm, mesoderm, and endoderm, arranged in a haphazard manner2, immature teratomas are the only germ cell tumour that are histologically graded based on the amount of neuroepithelium, the most common tissue in immature teratomas.10 Serum AFP is significantly raised in tumours that contain foci of yolk sac tumour.
Growing teratoma syndrome occurs during or after chemotherapy when an enlarging mass is found in the peritoneum, retroperitoneum, liver or lung. They contain mature cell types. The aetiology is not understood.
· MR imaging findings
Immature teratomas are complex unilateral predominately solid masses. Containing fat, coarse irregular scattered calcifications and numerous cysts of varying sizes. Unlike mature cystic teratomas which have cysts mostly containing sebaceous fluid, the cysts in immature teratomas have similar densities to simple fluid (low T1 high T2) with enhancing soft tissue components.9-10
Table 6. MR characteristics of Immature Teratomas 9-10
T1 |
T2 |
T1+ contrast +fat sat |
-Fat (high T1T2) can be seen within cysts and as small foci within the solid mass.
-Small foci of fat can be detected using fat suppressed sequences.
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-Complex solid mass of varying T2 signal.
-Contains cystic areas which have signal intensities similar to simple fluid.
-Irregular scattered calcification present. Can be difficult to identify (low T1T2) |
-Enhancing soft tissue components.
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· MR Imaging findingsFig. 12: T1 axial shows fat scattered between multiple cysts of varying sizes in keeping with an immature teratoma.It is difficult to appreciate the punctate irregular calcifications.
Fig. 13: T2 axial shows fat scattered between multiple cysts of varying sizes consistent with an immature teratoma. It is difficult to appreciate the punctate irregular calcifications.
Fig. 14: STIR shows multiple cysts and fat with markedly hypointense foci consistent with calcifications
Fig. 15: T2 coronal shows a large mass with fat and numerous cysts of varying sizes.
Fig. 16: T1 post contrast Fat Sat shows a large mass with enhancing soft tissue components,numerous cysts and fat.
Fig. 17: CT coronal shows the scattered irregular calcifications seen in immature teratomas
Fig. 18: Abdominal radiograph shows the scattered irregular calcifications seen in immature teratomas.
Differential Diagnosis for a complex mass10
-Mature Cystic Teratoma-smaller predominately cystic with dense calcifications unlike immature teratomas (larger containing small foci of fat and scattered calcifications)
-Mature Solid teratoma-does not have immature components however indinguishable and therefore has to be extensively sampled at biopsy to exclude an immature teratoma.
-Ovarian Cancer-frequently bilateral without detectable fat on imaging modalities. Occurs in older patients. Most present with peritoneal carcinomatosis.
-Tubo-ovarian abscess-symptomatic with abdo/pelvic pain, vaginal discharge. Thick walled cystic mass with inflammatory stranding ascites without fat.
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Take Home Message
Consider when there is a large unilateral ovarian mass with scattered calcification, fat, solid enhancing components and numerous cysts of varying sizes.