·     
Sertoli-Leydig cell tumors

They account for only 0.5%
of malignant ovarian neoplasms in children. They affect patients 90% (80). Even advanced stage MGCTs have good
prognosis due to high sensitivity to chemotherapy.

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·     
Dysgerminoma

Dysgerminoma is the most
common malignant germ cell tumor. It is frequently accompanied by nonspecific
elevation of serum LDH. On T2WI, dysgerminoma
is typically an intermediate-to-high SI solid mass with several lobules that
are separated by low SI fibrovascular septa which enhance avidly following IV
contrast medium administration (79) (Figure xx).

·     
Immature teratoma

Immature teratoma is
considered the second most common MGCT and tend to occur in 2 forms: primary
immature teratoma and malignant transformation of a mature cystic teratoma.
Malignant transformation occurs in less than 2% of mature cystic
teratomas.  Several MRI features may
distinguish rare immature teratoma from common mature cystic teratoma. First,
immature cystic teratoma is cystic, whereas immature teratoma is
characteristically a solid mass with cysts. Second, cysts in mature cystic
teratoma typically contain fatty sebaceous fluid, whereas cysts are
predominantly simple fluid in immature teratoma (Figure xx). Third, both tumors
contain fat which has high SI on T1WI and low SI on fat-saturated T1WI. In
immature teratoma, foci of fat are smaller and interspersed throughout a solid
mass. Finally, calcifications are seen with both tumors (best visualized on CT
and detected on MRI as low SI on T1WI and T2WI), but their morphology differs
between two tumor types. In mature cystic teratoma, calcifications are coarse
or tooth-like; in immature teratoma, calcifications are smaller and scattered
diffusely throughout a solid mass (100).

·     
Endodermal Sinus tumors (Yolk sac tumors):  

Endodermal sinus tumors are the third most common
malignant germ cell tumour. They are usually unilateral rapidly growing tumors (101). The classic MRI features includes a large, complex mass that extends
into the abdomen and contains both solid and cystic components. They can be
associated with prominent signal voids on non-enhanced images as a results of tumor
vascularity.

·     
embryonal carcinoma:

 Embryonal carcinomas are
extremely rare and usually found as part of a mixed germ cell tumor. These
lesions are predominantly solid and unilateral with extensive areas of
hemorrhage and necrosis. Serum level of B-hcg and AFP can be elevated. 

·     
Choriocarcinoma : 

Choriocarcinomas are rare
and aggressive tumors which usually have metastasized widely to the lungs,
liver and bone by the time of presentation. Classic appearance is a
unilateral solid pelvic mass with extensive necrosis and hemorrhage and
increased B-hcg (102).

Teaching points: Malignant germ cell tumors

 

–       
Malignant Germ cell tumors account for less than 5% of
all ovarian neoplasms

–       
Malignant Germ cell tumors usually present in the
first or second decades of life and grow rapidly

–       
Dysgerminomas are the most common malignant germ cell
tumour. On T2WI, dysgerminoma is typically an
intermediate-to-high SI solid mass with several lobules that are separated by
low SI fibrovascular septa which enhance avidly following IV contrast medium
administration.

–       
Choriocarcinomas are rare, aggressive tumors which
have usually metastasized widely by the time of presentation.

–       
Unlike epithelial ovarian cancer—in which intraperitoneal
dissemination is the most com-mon mode of spread, and approximately 70% of
patients have peritoneal metastases at staging laparotomy—lymphatic spread is
the most common mode of spread among MGCTs

 

1-    
Tumor Staging

Ovarian cancer is surgically staged, mostly according
to the FIGO classification which was updated in 2014. This classification
applies to epithelial ovarian cancer but also to sex-cord stromal and germ cell
malignancies. The various FIGO stages are presented in Table 4 (103-105).

Update of the new FIGO classification:

–      
Fallopian tube, primary peritoneal and ovarian tumors
are now considered collectively. On imaging, the differentiation between
fallopian tube and ovarian tumor is sometimes difficult; the update in this
classification make the radiologist assessment easier. Note that stage I primary peritoneal
cancer does not exist.

–      
Stage IC has now been subdivided to specify
intraoperative rupture (IC1) or preoperative rupture (IC2) with malignant
ascites or positive peritoneal washings (IC3). Once capsular rupture is noted,
peritoneal washing and cytology studies are recommended.

–      
Stage II is considered now as solely pelvis confined
tumor and as such has eliminated stage IIC (IIA or IIB with positive findings
from pelvic wash or ascites). Note that due to its anatomic position within the
pelvis, metastasis to the sigmoid colon is considered stage II.

–      
The new staging classification also leads to the
clarification of the lymph node status. Less than 10% of ovarian carcinomas
extend beyond the pelvis with exclusively retroperitoneal lymph node
involvement. Evidence in the literature indicates that these cases have a
better prognosis than that of tumors with abdominal peritoneal involvement. The
new staging includes a revision of stage III patients and assignment to stage
IIIA1 based on spread to the retroperitoneal lymph nodes without
intraperitoneal dissemination.

–      
Stage IV is defined as distant metastatic disease.
This stage has now been divided into IVA (patients with pleural effusion with
positive cytology) and IVB (parenchymal liver or splenic metastases, and
extra-abdominal metastases including inguinal and supraclavicular lymph nodes
as well as those with transmural involvement of visceral structures).

 

2-    
Evaluation of Pattern of Spread

In this
chapter, we will focus on HGSC which is the most common type and usually
detected at advanced stage. Ovarian carcinoma frequently spreads through direct
extension to surrounding pelvic tissues. Tumor may metastasize beyond the
pelvis via three mechanisms: intraperitoneal spread, lymphatic invasion, and
hematogenous dissemination; intraperitoneal dissemination is the most common
mode of tumor spread in ovarian cancer.

Four questions
need to be assessed by the radiologist in the settings of HGSC (106):

1-Is there peritoneal extension?

2-Is there disease in sites that decrease the
likelihood of optimal debulking?

3-Is there disease in sites where dedicated surgical
expertise?

4-Is there disease in sites beyond the scope of the
surgeon?

 

1-Is there peritoneal
extension?

Bulky nodules within
the greater omentum classically called as “Omental caking” are easily detected.

Early peritoneal
carcinomatosis can be missed on imaging especially if subtle sign are not carefully
checked (106):

-Ascites in the
upper abdomen may be the early and sole indicator of peritoneal carcinomatosis
especially if loculated.

– Subtle peritoneal
thickening, fine reticulonodular pattern, nodularity along peritoneal surfaces
may indicate metastatic involvement  (figure xx).

– In advanced
cases, peritoneal deposits have a variable appearance from plaque like to
nodule or confluent masses.  

– Calcifications
known as psammoma bodies may be detected

 

2- Is there
disease in sites that decrease the likelihood of optimal debulking?

Validated
guidelines regarding surgical criteria for inoperable disease are still
missing. Multiple scoring systems attempting to predict the likelihood of
optimal resection have been published (107-114). Yet, the choice between neoadjuvant therapy versus
primary debulking is strongly dependent on the degree of surgical of expertise
and the disease extension. Optimal cytoreduction is usually defined as less
than 1cm residual disease. Our role as radiology, is mainly to alert the
surgical team on the volume and the location of the disease may decrease the
likelihood of “optimal debulking”.