|ECR 2018 / C-2915|
|Imaging spectrum of non-epithelial ovarian tumors: a road less travelled|
Findings and procedure details
We reviewed our institutional data base for patients with an operation for ovarian mass in our gynecologic oncology unit between January 2013 and September 2017. 123 patients had pathological diagnosis of ovarian tumor other than surface epithelial tumor with mostly being mature cystic teratomas.
Sex-cord stromal tumors, germ cell tumors and secondary tumors (malignant, not otherwise specified) have histologic origin rather than ovarian surface epithelium ( Fig. 2 ).
1. Sex cord- stromal tumors
Ovarian stroma is composed of granulosa cells, theca cells, fibroblasts, Sertoli cells and Leydig cells. Tumors originating from those cells may give rise to granulosa cell tumors (adult/ juvenile type), thecoma, fibroma/fibrosarcoma, Sertoli cell tumor or Leydig cell tumors, respectively.
Granulosa cell tumors (GCT):
· GCTs derive from the cells surrounding the developing follicles.
· They account for 70% of all sex-cord stromal tumors, but only 2-3% of all ovarian neoplasms.
· They are considered as low grade malignancy. Recurrence may be seen after surgical resection. Inhibin-b and Estradiol may rise.
· They usually occur in middle-aged and postmenopausal women.
· They are almost always unilateral tumors.
· In imaging, they may present as a complex cystic mass or a complex mass containing solid, fibrous portions, hemorrhage, and cystic components  ( Fig. 3 ).
· Solid components show intermediate T2 signal intensity, restricted diffusion and avid contrast enhancement.
· Abnormally thickened endometrium may be seen secondary to estrogen secretion by the tumor.
Thecoma- Fibroma group
· This group represent benign solid ovarian stromal neoplasm named as fibroma, thecoma and fibrothecoma
· They are the most common primary solid tumors of the ovary in asymptomatic women .
· Fibromas are typically solid tumors with low T2 signal and low grade enhancement.
· Ovarian fibroma may be associated with Meigs syndrome (pleural effusion or ascites) ( Fig. 6 ).
· Thecomas seem as solid mass with intermediate T2 SI which can show restricted diffusion. Estrogen secretion by the tumors can cause endometrial thickening
· Fibrothecomas may show heterogenous T2 hypointense SI with cystic changes ( Fig. 7 ). No enhancement or delayed homogenous enhancement may be seen ( Fig. 8 ). Diffuse diffusion restriction may be seen in DWI. They may exist with other tumors of the ovary ( Fig. 9 ).
Sertoli-leydig cell tumors
· These tumors are low grade malignancies with stromal cellular origin
· At MR imaging, Sertoli-Leydig cell tumors appear as solid masses with cystic or necrotic areas and solid components with T2intermediate signal intensity. Their signal intensity on T2-weighted images reflects the extent of fibrous stroma .
· AFP is usually raised.
· Solid components show enhancement.
· Diffusion restriction is not significant
2. Germ cell tumors
Primitive germ cell tumors
o Most common malignant germ cell tumor in adolescents and young adults, which is analogous to testicular seminoma.
o It presents as a solid tumor with intermediate T2 SI with cystic areas ( Fig. 10 ).
o It demonstrates homogenous enhancement and diffusion restriction in solid components.
o LDH and placental ALP may increase.
· Yolk sac tumor
o It is a highly malignant tumor of germ cell origin.
o AFP is usually raised.
o It is presented as heterogenous solid-cystic tumor with intermediate T2 SI and high T1 SI areas.
o It demonstrates heterogenous enhancement and diffusion restriction in solid components.
· Embryonal carcinoma: Could not be differentiated from other malignant germ cell tumors
· Mixed germ cell tumor
o They show variable appearances depending on predominant cell type. b-HCG and AFP may rise depending on the cell types.
o They mostly present as large solid lesions which show restricted diffusion and enhancement ( Fig. 11 ).
Biphasic or Triphasic Teratoma
· Immature Teratoma
o These tumors are malignant solid-cystic tumors with immature germ cell origin. They are usually seen in adolescents and young adults. AFP and b-HCG may rise.
o They may contain macroscopic fat and calcification scattered in solid parts ( Fig. 12 ).
o Solid components show avid contrast enhancement and diffusion restriction.
· Mature teratoma:
o They are classified as solid, cystic (dermoid cyst) and fetiform teratoma
o Mature teratomas are benign tumors derived from at least 2 different germ cell tumors
o CA 19-9 may rise.
o In imaging, macroscopic fat, fat-fluid or fluid-fluid levels are usually seen ( Fig. 13 ). Calcification may accompany. Rokitansky nodule is seen as a protruding mass from one side of the wall.
o Floating balls made up of fat, keratin or hair may be seen ( Fig. 14 )
o They may show moderate diffusion restriction according to the viscosity of the fluid in the cyst ( Fig. 15 ).
Monodermal teratoma and somatic-type tumors associated with dermoid cysts
· Struma ovarii, carcinoid tumor, neuroectodermal tumor, carcinoma, melanocytic group, sarcoma group, sebaceous tumor group are subgroups according to histologic cell type of origin.
· Struma ovarii is the most common form of monodermal teratomas. Thyroid tissue is found more than 50% in the specimens. In imaging, is it usually seen as a multicystic mass with high T1 areas regarding thyroid tissue and very low T2 signal areas regarding viscous colloid ( Fig. 16 )
· Carcinoids frequently co-exist with teratomas.
3. Malignant, not otherwise specified
Metastatic cancer from non-ovarian primary
· Variable appearances occur according to primary malignancy.
· Usually malignant solid-cystic lesions are seen in the ovaries ( Fig. 17 ). In early metastatic disease, nodules over ovarian capsule may be seen. When the colon or appendix is primary, multiloculated cystic lesion may be seen in which differential diagnosis covers mucinous ovarian neoplasms ( Fig. 18 ).
· Solid components show intense enhancement and diffusion restriction.
· Hematologic malignancies (e.g. lymphoma) may cause bilateral solid lesions with low T2 SI with accompanying lymph nodes ( Fig. 19 ).
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