Teaching Case

Female paediatric patient of 14 years of age presented at the emergency department with pelvic pain lateralised to the right that worsened with defecation and urination. Negative laboratorial study for infection. No relevant risk factors or antecedents.

Pelvic ultrasound revealed an adnexal heterogenic mass with predominant hypoechogenic pattern with calcifications, measuring 10x9 cm. (Fig. 1)
A consequent pelvic CT was performed as the patient suffered a symptomatology aggravation and a torsion of the previously described mass was suspected. The CT revealed a large pelvic mass, mostly hypoattenuating but with areas of calcification and variable enhancement after contrast. Its origin appeared to be adnexal but further characterisation with MRI was subsequently performed as the symptoms were controlled. (Fig. 2)
On MRI, the mass had a well-circumscribed low signal intensity rim on T2-weighted images, a homogeneous low signal intensity on T1 and heterogeneous signal intensity on T2, with areas of scattered hyperintensity representing cystic degeneration. (Fig. 4)
Surgical resection was performed and histologic evaluation was requested, revealing a histological specimen compatible with right ovarian fibroma.

Ovarian tumors are rare in the paediatric population, however, they must be considered in patients with abdominal pain and palpable mass. Although rare, they are the most common genital tumour, accounting for 60%–70% of all gynaecologic malignancies between the ages of 10-19 years. [1, 6]
Ovarian tumours occurring in the paediatric population encompass a multiplicity of benign and malignant tumours such as germ cell tumours (GCTs), surface epithelial stromal tumours, sex cord–stromal tumours (SCSTs) and others as gonadoblastoma, malignant lymphoma or leukaemia.

SCSTs originate from the coelomic epithelium and ovarian stroma. They account for 10-20% of all paediatric ovarian tumours and have a particular incidence in patients younger than 15 years. [1]

Ovarian fibromas are the most common SCSTs in adult women and account for 4% of ovarian tumours, however, they are extremely rare in the paediatric population. [2, 5]

The patients are generally asymptomatic so they present with large masses detected at palpation or with abdominal/pelvic pain due to compression of other structures.

They are solid masses and therefore extremely important from an imaging standpoint as they have to be considered in the differential diagnosis of malignant tumours. [2]

Ovarian fibromas are composed of intersecting bundles of spindle cells without theca cells or oestrogenic effect, unlike fibrothecomas. [3]

Ultrasound (US) remains the study of choice in the initial evaluation of suspect adnexal masses, as it is cheap, noninvasive, and widely available. [2] At US, fibromas most commonly manifest as solid, hypoechoic masses with sound attenuation. However, the US appearance is variable, and hyperechoic masses with increased through-transmission and calcifications may be seen. [3]

At CT, fibromas are usually diffuse hypoattenuating masses and show poor enhancement after contrast media injection.

At MRI, they usually present as well delimited, homogeneous, relatively low signal intensity either on T1-weighted and T2-weighted images. This low signal intensity results from the abundant collagen content of these tumors and is relatively diagnostic for fibroma.
Larger lesions (> 6 cm) show more frequently degenerative and oedematous changes. [5] These are scattered high-signal-intensity areas on T2-weighted images. [3] Thus, the presence of pseudocapsule, degenerative changes, peripheral subcapsular cystic areas, heterogeneous T2 signal, and heterogeneous enhancement are more common with larger fibromas.

The association of ovarian fibromas with syndromes has been postulated, such as in Nevoid Basal Cell Carcinoma Syndrome or in Meig Syndrome. [3, 4] Thus, a genetic workout must be provided to these patients (in this particular patient, no association was found).