A previously healthy premenarchal 9-year-old girl presented to the emergency department after the patient’s mother felt a nontender abdominal mass that had been noticeably larger and growing for the past week. The patient was initially evaluated by her pediatrician and subsequently had an outpatient abdominal ultrasound that revealed a large abdominal mass (Figure 1). Follow-up CT was also ordered by the primary team (Figure 2). She had a good appetite, good energy, and was able to participate normally in daily activities. Family history was negative for malignancy.
Solid mass with intrinsic areas of necrosis in the lower abdomen and pelvis, most likely arising from the adnexa, and ovarian in origin.
Although ovarian tumors in children are uncommon, with an estimated incidence of 2.6 cases per 100,000 girls per year,1 enlarging abdominal masses in the premenarchal female pediatric population should raise suspicion for ovarian origin. Sonographic images revealed a large, well-marginated, lobulated solid mass with internal cystic components. Further evaluation with contrast-enhanced CT of the abdomen and pelvis demonstrated a large lower abdominal/pelvic mass that appeared to arise from the adnexa. The heterogenous mass was well-marginated and had enhancing solid components and extensive areas of necrosis. Although germ cell tumors (GCTs) share imaging characteristics, the heterogeneous enhancing solid lesion with extensive necrosis, in addition to rapid growth per clinical history, suggested a GCT such as a yolk sac tumor (YST). Dysgerminoma was less favored since fibrovascular septa were not appreciated on the imaging. Teratoma was unlikely given the lack of calcifications or fat. For ovarian masses, tumor markers such as alpha-fetoprotein (AFP), beta-human chorionic gonadotropin (b-hCG), cancer antigen 125 (CA-125), inhibin A and B, and carcinoembryonic antigen (CEA) can be obtained to aid in diagnosis and for postsurgical follow-up. For this patient, only AFP was significantly elevated at > 20,000 ng/mL. Given imaging findings and elevated AFP, YST was the primary differential diagnosis.
YST, also known as an endodermal sinus tumor, is a rare malignant GCT that usually occurs in the second and third decades of life, with an average age of 19 years. 1 YST is the second most common malignant GCT, and abdominal pain or mass is the most common presenting complaint. In early stage disease, they are usually unilateral. Due to their rapid growth, duration of symptoms is usually 1 to 4 weeks. 4,5 Because the tumor produces AFP, this tumor marker can be used at initial diagnosis and for postoperative follow-up.
Plain films can demonstrate a pelvic mass with mass effect on adjacent bowel loops. Sonography usually shows a large pelvic mass that extends into the abdomen with both solid and cystic components. Sometimes, concurrent dermoid cyst of the ovary, ascites, or urinary obstruction can be seen as well.4 CT and MR imaging often demonstrate a large heterogeneous solid mass with intrinsic cystic components representing necrosis and hemorrhage. MR imaging can better detect intratumoral signal voids and intratumoral hemorrhage.
Pathologic features include extensive areas of hemorrhage and necrosis. Treatment can include conservative surgery with multiagent chemotherapy.
Ovarian dysgerminoma is identical to testicular seminoma, originating from undifferentiated germ cells. It is the most common malignant GCT in children and usually occurs in the second and third decades of life, although 10% can occur in the first decade. Lactate dehydrogenase (LDH) is a useful marker for diagnosis and follow-up. Rarely, b-HCG can be elevated.
Gross pathology often shows a well-encapsulated and lobulated solid tumor with a white to tan color. Irregular areas of necrosis, cystic changes, or calcifications can be seen. Intrinsic areas of hemorrhage can also exist, as in the case of YST.
Histologically, the tumor is composed of monotonous polygonal tumor cells aggregated into cords and clumps with abundant cytoplasm and flattened central nuclei. 1 Tumor cells are separated by fibrous or fibrovascular septa, which can be seen on imaging.
On imaging, dysgerminomas usually are multilobulated, well-marginated masses with prominent fibrovascular septa. Because of the fibrous component of the septa, these will appear hypointense on both T1- and T2-weighted images on MR imaging.3 In addition, the septa may show intense enhancement. Doppler imaging can show flow signal within the septa.1 Areas of necrosis, hemorrhage, or speckled calcifications can be seen. As opposed to other malignant GCTs, dysgerminomas can often be bilateral and can spread to retroperitoneal lymph nodes. 1
Embryonal carcinoma occurs primarily in children, with a median age of 14 years. The tumor can produce AFP and b-HCG, which can aid diagnosis and post-treatment follow-up. CT and MR imaging characteristics are nonspecific and share similarities to other malignant GCTs, as detailed above. Again, internal areas of hemorrhage, necrosis, and cystic components are common.
Ovarian teratomas are GCTs composed of mature or immature tissues derived from more than one of the three primitive embryonic layers (ectoderm, mesoderm, and endoderm). Benign teratomas comprise 67% of pediatric ovarian neoplasms and can be bilateral in up to 25% of cases.2
Mature cystic teratoma (MCT) comprises about 50% of all pediatric ovarian neoplasms. When ectodermal elements predominate, they are called dermoid cysts. MCT is the most common ovarian neoplasm in children. In 10% of pediatric cases, it can be bilateral. 1 Treatment for MCT is surgical excision with fertility preservation.
Imaging characteristics of MCT include a cystic adnexal mass that contains fat and/or calcifications. Ultrasound can reveal areas of echogenicity corresponding to fat, although this can be challenging to definitively determine. Helpful signs include the “tip-of-the-iceberg” sign represented by coarse shadowing calcifications; dermoid mesh seen as linear interfaces corresponding to hair; and a dermoid plug represented by an echogenic nodule with fat, hair, and teeth. However, sometimes CT or MR is needed for further characterization. Fat density can be definitively seen on CT. On MR imaging, hyperintense T1 signal with signal loss on fat-saturated sequences can confirm fat composition. Calcifications are often seen as well.
Immature teratoma affects a younger age group and frequently occurs between ages 10 and 20 with a median age of 17 years. It represents 10% to 20% of ovarian malignancies in the pediatric population.1 Elevated AFP has been reported in cases of immature teratoma. Imaging usually reveals a unilateral, large, heterogeneous, predominantly solid or mixed solid and cystic mass with scattered calcifications and fat.
Ovarian lymphoma is rare, accounting for less than 2% of all pediatric ovarian tumors.1 On CT and MR imaging, ovarian lymphoma is often seen as unilateral or bilateral predominantly solid masses with homogeneous enhancement and preserved ovarian follicles. Small cysts can be seen along the periphery or within the solid portions.1 Although signal intensity on MR imaging is variable, leukemic involvement can often demonstrate hypointense T2 signal, likely due to high levels of myeloperoxidase.1
Ovarian YST. The patient underwent right salpingo-oophorectomy without complications. The patient was also started on multiagent chemotherapy with subsequent decreasing AFP levels.
Ovarian tumors are uncommon in the premenarchal female pediatric population. Patients in this age group presenting with abdominal masses should raise suspicion for ovarian neoplasm. Predominantly solid masses arising from the adnexa seen on cross-sectional imaging suggest malignant lesions such as GCTs. Tumor markers are helpful in favoring one GCT over another as imaging characteristics often overlap. Ovarian YSTs are large, heterogeneous, well-marginated solid masses with intrinsic necrosis and hemorrhage. Fibrovascular septa should point toward dysgerminoma. Fat or calcifications suggest an ovarian teratoma. Lymphoma and leukemia can be in the differential diagnosis as well. Treatment includes conservative surgery and multiagent chemotherapy.
Dao T, Lai H. Abdominal Mass in a Female Pediatric Patient. J Am Osteopath Coll Radiol. 2021;10(3):21-23.
