An 18-year-old girl presented to the emergency department with worsening left hip pain that radiated down her leg after falling 2 months prior. She denied pain elsewhere. Pelvic radiographs revealed amorphous calcifications in the mid-pelvis without acute bony abnormality (Figure 1A). Subsequently, the patient underwent computed tomography (CT) of the abdomen and pelvis (Figure 1B), and pelvic ultrasound (Figure 1C) with findings that prompted surgical intervention (Figure 1D).
Ovarian mass with calcification and fat
Ovarian teratoma (mature and immature)
Other germ cell tumors
Sex cord stromal tumors
Epithelial tumors
Fat containing tumors
Ovarian lesions are a common etiology for pelvic masses in the pediatric population. Ovarian tumors are classified by the cell of tumor origin (germ cell tumors, sex cord stromal tumors, epithelial tumors). Multiple imaging modalities can be useful in differentiating ovarian masses and suggesting a diagnosis.
Mature ovarian teratoma account for 50% of pediatric ovarian tumors. They are germ cell tumors composed of mature well-differentiated tissue from the 3 germ cell layers (ectoderm, mesoderm, and endoderm).1 Clinical presentation of ovarian teratoma ranges from an incidental finding during imaging for unrelated symptoms (as in this case) to acute onset of pain as a result of ovarian torsion or tumor rupture. Patients typically present in the reproductive years. Ovarian teratomas can be bilateral in up to 10% of cases.2
Imaging findings vary from purely cystic masses to predominately solid lesions. Radiographs often suggest the diagnosis by revealing calcifications and mass effect. On ultrasound, the most typical manifestation is a complex ovarian cystic mass with an echogenic shadowing mural nodule (Rokitansky nodule) projecting into the lumen of the cyst.1 Other common ultrasound findings include echogenic components due to fat, linear echogenic bands from the presence of hair, and echogenic foci with posterior acoustic shadowing representing calcification or teeth within an ovarian mass. The “tip of the iceberg” sign describes visualization of the leading edge of the mass with distal acoustic shadowing preventing assessment of the deep margins.
The typical finding of cystic mass with intratumoral fat is also well seen on cross-sectional imaging. CT demonstrates adnexal mass with negative attenuation due to fat within it. Teeth/calcification, variable attenuation of tissue components, septations, and fluid-debris levels can also be readily detected.
On MRI, teratomas demonstrate mixed signal intensity. Low signal intensity can be present from hair or calcification. Intratumoral fat can be identified with T1-weighted imaging with and without fat saturation, demonstrating high signal intensity on T1 images and low signal on T1 fat-saturated images. Chemical shift imaging with in-phase and out-of-phase imaging is helpful in identifying microscopic intratumoral fat.1
Atypical manifestations of ovarian teratomas include absence of demonstrable fat, lesions consisting entirely of fat, combination tumors, and collision tumors. A combination tumor contains intermixed histologic components resulting from a common stem cell, for example, a mixed germ cell tumor. A collision tumor is defined as a tumor with 2 adjacent but histologically distinct tumors with no histologic admixture at the interface. The most common type of ovarian collision tumor is composed of a mature teratoma and a mucinous cystadenoma or cystadenocarcinoma.3
Ovarian teratomas can be associated with various complications including ovarian torsion, tumor rupture, malignant transformation, infection (typically Salmonella organisms), and autoimmune hemolytic anemia.1
Treatment of mature teratomas involves surgical resection with ovary- sparing surgery.
Immature teratomas represent < 1% of all germ cell tumors. Like mature teratomas, immature teratomas consist of tissue derived from all 3 germ cell layers.4 It is important to distinguish benign mature teratomas from malignant immature teratomas histologically; however, some imaging characteristics may suggest one or the other.
On CT and MRI, immature teratomas are typically large, complex, heterogeneous masses arising from the ovary with cystic and solid components. Calcifications are present and typically scattered through the lesion. Small foci of fat are also seen. Immature teratomas tend to be larger (mean diameter 12-35 cm) than mature teratomas (approximately 7 cm) at the time of diagnosis.1 These tumors grow rapidly, and frequently demonstrate capsule rupture.
Immature teratomas usually present at an earlier age than mature teratomas and have a worse prognosis.
Other germ cell tumors include dysgerminoma, endodermal sinus tumor, and choriocarcinoma.
Dysgerminoma is a rare ovarian tumor that occurs in young women; it is the ovarian counterpart of seminoma of the testicle. In its pure form, dysgerminoma is not associated with endocrine hormone secretion. However, syncytiotrophoblastic giant cells that produce human chorionic gonadotropin (hCG) are present in 5% of dysgerminomas. On imaging, a multilobulated solid mass is seen with vascular septa. Calcifications may be present, usually in a speckled pattern.4 Dysgerminomas are most often unilateral.5
Endodermal sinus tumor (also known as yolk sac tumor) is a rare, malignant ovarian tumor. This tumor usually occurs in the second decade of life. On imaging, the tumor manifests as a large complex pelvis mass with both cystic and solid components. Affected patients have elevated alpha-fetoprotein.4 Most cases of endodermal sinus tumor are unilateral with approximately 1% being bilateral.6
Choriocarcinoma is an aggressive tumor that accounts for < 1% of ovarian tumors. This tumor can occur during pregnancy but not always (gestational or nongestational). Nongestational choriocarcinomas typically occur in children and young adults. Imaging findings include a unilateral, hypervascular, solid tumor with cystic/necrotic and hemorrhagic component. Elevated serum hCG is characteristic.5
Sex cord stromal tumors in the pediatric population include juvenile granulosa cell tumor (GCT) and Sertoli Leydig cell tumor.
GCT is the most common estrogen-producing ovarian tumor. There are 2 subtypes: adult (95%) and juvenile (5%).5 These tumors are typically unilateral, but 2% to 5% of the juvenile cases can be bilateral.2 They can have various imaging characteristics, including multilocular cystic lesions with solid components, solid masses, solid mass with sponge-like (“Swiss cheese”) appearance, and cystic tumors with a thick rind of soft tissue. The majority of patients present with endocrine dysfunction related to hyperestrogenism, including premature breast development, clear vaginal discharge, atypical uterine bleeding, pubic or axillary hair growth, and accelerated skeletal maturation. Juvenile GCT can also rarely present as a virilizing tumor.2
Sertoli-Leydig cell tumors can occur in young woman (< 30 years-old) accounting for < 1% of primary ovarian neoplasms.5 Patients often present with virilization due to androgen activity (oligomenorrhea, atrophy of breast tissue, acne, increasing facial hair). Sertoli-Leydig cell tumors have a heterogeneous imaging appearance, including both cystic and solid components.5
The most common epithelial ovarian tumors are serous and mucinous tumors, both of which are rare in prepubescent patients.4 Epithelial tumors can have a spectrum of pathology from benign to malignant. The 2 most common types of epithelial tumors are difficult to differentiate on imaging, as these tend to contain both cystic and solid components.
Other fat-containing tumors, besides teratoma, include lipoblastoma and liposarcoma. The majority of patients with lipoblastoma present before age 3 with a painless, enlarging mass. Imaging of lipoblastoma typically shows a well-circumscribed lesion containing predominately fat. These masses tend to be encapsulated with internal septations.7 Liposarcomas are fatty masses that can present with a variable volume of fat and soft tissue, depending on the subtype.7 Liposarcomas are rare in the pediatric population.
Ovarian cysts are very common and can be bilateral, but should not have any solid components. Scrutiny of the wall of the cyst on ultrasound, CT or MRI to exclude a mural nodule or any vascular component is required. In questionable cases, a short interval follow-up ultrasound is recommended to show expected involution of a non-tumoural cyst.
Bilateral ovarian mature teratomas
Ovarian lesions are a common source of pelvic masses in children and adolescents. Mature ovarian teratomas are benign masses that account for half of pediatric ovarian tumors. Clinical presentation varies from asymptomatic to symptoms related to torsion or rupture of the lesion. Mature teratomas typically present on imaging as cystic masses with intratumoral fat, which are helpful differentiating features from other less common ovarian masses in the pediatric population.
Person A, Soldes O, Gaisie G. Solid Ovarian Mass in an Adolescent. J Am Osteopath Coll Radiol. 2016;5(1):26-28.
