Malignant transformation, torsion and rupture in a mature cystic teratoma of the ovary, a case report

A 83-year-old female patient presented at the emergency department with generalised abdominal pain, nausea and vomiting episodes. A physical examination showed features of an acute abdomen with abdominal defense. Blood tests revealed mild leukocytosis and slightly increased PCR.

Abdominal X-ray: radiolucent pelvic mass containing bone structures and mural calcifications (Fig.1).

Ultrasound: complex cystic adnexal mass with fluid-fluid levels, echogenic bands and twinkling artifact with colour Doppler, highlighting the presence of calcifications (Fig.2).

Post-contrast abdominopelvic CT: pelvic mass presenting mural calcifications. Inside the lesion there were fluid-fluid and fat (both solid and liquid)-fluid levels, and a calcified protuberance projecting into the lesion cavity highly suggestive of being a Rokitansky nodule (Fig.3a).

Acites, floating areas of fat attenuation around the liver (Fig.3c), cyst wall discontinuity and calcic images (teeth) outside the mass, suggested rupture (Fig.3b). In addition, a slight deviation of the uterus and signs of periuterine vascular engorgement were observed (Fig.3d).

The patient underwent surgical extirpation of the lesion and pathologic results demonstrated a mature cystic teratoma complicated with torsion, haemorrhagic infarction and rupture. There were also signs of malignant transformation, since histopathologically analysis revealed keratinizing squamous carcinoma data (Fig.4).

Although most of the occasions are benign, slow-growing and asymptomatic lesions, mature cystic teratomas can be associated with several complications, including torsion (16%), rupture (1%–4%), malignant transformation (1%–2%) and infection (1%) [5], that require different therapeutic strategies.
Torsion is the most common complication, and the most specific imaging findings include a twisted vascular pedicle with engorged vessels, fallopian tube thickening and uterine deviation. Another possible complication is rupture, which causes a leak of fatty material that irritates the peritoneum, being possible the appearance of a chemical peritonitis known as gliomatosis [5, 6]. Using ultrasound, CT or MRI it is possible to demonstrate the discontinuity of the wall, a distorted morphology of the lesion as well as ascites [5]. It is important not to confuse fat bubbles with intraperitoneal free air.
Malignant transformation of mature cystic teratomas is rare, and it occurs in 0.17-3% of cases [3, 4]. Most of the cases described are squamous cell carcinomas (80-90%), whereas adenocarcinoma accounts for 5% cases [3]. Other malignant transformations include melanoma, carcinoid tumours and others [2].
Risk factors that have been associated to malignant transformation are patient age, tumour size, ultrasound and computed tomography characteristics (invasive growth marginated soft-tissue components through the tumour wall or irregular soft-tissue enhancing components within the mass) and elevated levels of SCC and CA125 [1, 2, 4]. However, only 1-2% cases can be preoperatively diagnosed. Its low incidence and absence of specific signs, similarity to mature cystic teratoma may difficult its diagnosis until histopathology study [2].
Given the non-specificity of the clinical manifestations in complicated ovarian teratomas, as it happened in the case that we describe, it is vital for the radiologists to be familiar with the imaging findings of these possible complications, in order to be able to carry out an adequate therapeutic management.