Pathological features and imaging of ovarian goiter

Let's start with a case:

Female, 18 years old, with unprovoked symptoms
such as bloating and poor appetite before 1 month.
Previous menstrual regularity, 3-4 days/30 days
.

Extrahospital ultrasound: the left adnexal area is about 10×7 .
6cm mixed echo, irregular morphology, no echo of different sizes of internal probe, clear boundaries, internal exploration and blood flow signal
.

Blood CA125 1147U/ml

Non-contrast abdominal CT + contrast scan is performed

Left ovarian cystic solid mass, flat scan density mixed, multilocular cystic cavity of varying sizes, from low to higher density; The solidity of the enhanced scan is significantly enhanced
.
Lots of ascites
.

Final diagnosis: left ovarian goiter

Ovarian goiter

It is a rare benign ovarian tumor that originates in ovarian germ cells
.
The tumor is mainly composed of thyroid tissue and is a monodermal teratoma, accounting for about 2.
7%
of mature teratomas.
Ovarian mature teratomas contain thyroid components in 5%-20%, and SO
is diagnosed when the tumor contains more than 50% thyroid components.

The incidence of SO is low and clinically rare
.
Patients are often asymptomatic, most of them are treated by physical examination or abdominal and pelvic masses, and a few cases are accompanied by thyroid enlargement or hyperthyroidism, and the corresponding symptoms disappear
after surgery.
Some patients may present with Meigs syndrome, which is accompanied by chest, ascites, and even elevated
serum CA125.

It usually occurs unilaterally and is less common
on both sides.
Histologically broadly similar to cystic teratomas, it is generally smooth, lobulated or separated, and the solid part may consist entirely of thyroid tissue, with the cyst cavity filled with fluid or amber
.

Imaging findings and associated pathological features:

(1) Most of them are unilateral adnexal lesions with clear
boundaries.

(2) The mass is mostly cystic (cystic) or cystic, and pure solidity is rare
.
The density of fluid in the capsule is higher (CT value > 40HU), and some of the higher density cyst cavity (CT value 70~90HU) can be seen, which is related
to the strong attenuation X-ray ability of thyroglobulin and thyroid hormone rich in follicles.

(3) The solid part of the enhanced scan (including the cyst wall and septum) is strengthened to varying degrees or significantly strengthened
by thyroid tissue.
Pathologically these solid components consist of
mature thyroid tissue, a large number of blood vessels and fibrous tissue.

(4) The very low signal region and the obvious enhancement of solid components on T2WI are two typical MRI manifestations
of SO.

(5) The signal intensity of T2WI cystic zone depends on the concentration of substances in the capsule, when the contents are highly concentrated with high viscosity and gelatinous substances, T2WI shows extremely low signal, and when the cyst contents are diluted, T2WI shows high signal
.

Fig.
1 Female, 69 years old, non-contrast CT showed pelvic cystic solid mass, multiple cystic cavities, and scattered punctate calcification of the cyst wall; After enhancement, the solid nodule is significantly strengthened, and the cyst wall and septum are also strengthened
.

Fig.
2 Female, 30 years old, CT non-contrast scanning pelvic cystic solid mass (cystic), with separation, the right side of the separation cyst is uniform and high-density, CT value 78HU; After enhancement, a few strip-like, small nodular solid components were seen in the wall of the left capsule of the partition, which was significantly strengthened, and there was no strengthening
in the capsule on both sides of the separation.

Fig.
3 Female, 66 years old, solid small nodule (arrow) in the right adnexal area on non-contrast CT scan; The nodule is significantly strengthened (arrow)
after enhancement.

Fig.
4 Female, 31 years old, cross-sectional fat inhibition of T2WI, lesions are multilocular cystic, and one of the small sacs has very low T2 signal; Fat enhancement inhibited coronary surface T1WI, and the cyst wall and septum were strengthened, and no enhancement
was seen in the large and small cyst cavities.

Differential diagnosis:

(1) Ovarian endometriosis cyst: patients are mostly women of childbearing age, often have a history of dysmenorrhea, CT is mostly manifested as bilateral adnexal multi-locular cystic density opacity, the boundary can be unclear, often accompanied by adhesions, intracapsular density varies with different bleeding time, and the wall of the enhanced scanning capsule can be strengthened to varying degrees; SO has no dysmenorrhea, the lesion has smooth edges, clear boundaries with surrounding tissues, and no obvious strengthening
of the wall of the enhanced scanning capsule.

(2) Pelvic abscess or fallopian tube ovarian abscess: often abdominal pain, fever and elevated white blood cells, anti-infection treatment is often effective, enhanced scanning abscess wall is often significantly strengthened, the wall is thick, and exudative changes
can be seen around.

(3) Ovarian cord stromal tumor: it needs to be distinguished from SO when the cyst is obvious, but the cystic area of ovarian cord stromal tumor is often multiple fissures or sheets, the proportion of solid components in the tumor is often higher than 50%, the enhanced scanning ovarian cord stromal tumor is mostly slightly progressively strengthened, and the soft tissue density in the SO capsule is mostly thyroid-like and obviously uniformly strengthened
.

(4) Ovarian cystadenoma: divided into serous cystadenoma and mucinous cystadenoma
.
Serous cystadenomas are mostly single-locular cystic masses, with uniform cystic fluid density, watery density, thin cyst wall, no separation or slenderness in the capsule, and easy to distinguish from cystic SO; The thickness of the cyst wall and the intracystic septum of mucinous cystadenoma is uneven, the density of the capsule between different compartments can be uneven, and the cystic fluid can contain mucin and be high-density; It is difficult to distinguish from cystic SO, and the high-density cyst cavity and T2 very low signal capsule cavity on CT are helpful in the diagnosis
of SO.

(5) Ovarian cystadenocarcinoma: more likely to occur in elderly patients, mostly cystic solid, irregular thickening of the cyst wall or spacing, irregular morphology of solid components, unsmooth and sharp boundaries of cystic areas, often accompanied by abdominal pelvic effusion, which can be accompanied by lymph node enlargement, CA125 significantly increased; The SO interval is smooth, most are not accompanied by ascites, and CA125 is normal
.

Ovarian goiter rarely undergoes malignant transformation, is more common in menopausal women, and the imaging findings are mostly cystic solid masses, mainly solid components, and are non-specific
compared with other ovarian malignancies.

In summary, ovarian goiter (struma ovarii, SO) is a mature teratoma composed entirely of thyroid tissue or dominated by thyroid tissue (>50%), which is a highly specific ovarian monodermal mature teratoma, which is rare and has a low
rate of malignant transformation 。 Imaging features: (1) unilateral cystic solid or multilocular cystic lesions; (2) The solid part or thickened cyst wall is significantly strengthened after strengthening; (3) High-density cystic cavity (CT value 70~90HU) can be seen in the lesion, and it is not strengthened after enhancement; (4) Very low signal sacs were visible in the lesion on MR T2WI, and the enhanced scanning was not enhanced; (5) Punctate calcification or cyst wall calcification
can be seen in the lesion.