Teaching Case

The patient presented at the emergency department with strong abdominal pain and vomiting. The gynaecologist discovered, with ultrasound, a large uterine heterogeneous cystic mass and transvaginal hysterectomy was performed next day. But after the hysterectomy no cystic mass was found so a computed tomography was performed.

Abdominal CT (computed tomography) findings were an 8 cm cystic mass, with calcification of its capsule and dermoid growth within it from the right ovary, and free peritoneal fluid (Fig 1a, 1b). Negative HU values of cystic liquid content suggested a mature teratoma so IV contrast media (CM) was administered (Fig 2a). After CM administration, we found a slight capsule enhancement of the cystic mass and no other changes in HU values of its content (Fig 1c, 1d). Liquefied fat, dermoid plug content and calcification of cystic mass capsule were strong findings for a mature teratoma. The imaging diagnosis was confirmed by histology after surgical removal of the right ovary and its mass.

Dermoid cysts, also known as mature cystic teratomas or dermoids, are benign germ cell tumours. [1] They account for the most common ovarian neoplasm in women of reproductive age and may be bilateral in approximately 10% to 15% of cases. Although teratomas can occur at any age, they typically affect a younger age group than epithelial tumours and are the most common ovarian tumours in children. [2]
The vast majority of these tumours contain liquefied fatty material and hairs within the cyst cavity, or there is adipose tissue within the cyst wall or the dermoid plug. The latter, which is a mural solid protuberance, may also contain bone or teeth in up to 25% of cases. [1, 2]
Benign teratomas tend to grow slowly, and 60% of these tumours measure 5 to 10 cm. Rarely, giant dermoids - up to 40 cm - may be encountered. [1] The majority of benign teratomas are found incidentally. Complications, in order of decreasing frequency, include torsion (16%), chemical peritonitis due to rupture, and infection. Malignant degeneration of benign teratomas is rare (1% to 2%), usually occurs in elderly women, and originates from the dermoid plug (Rokitansky nodule). [1] The specific MRI and CT feature of a dermoid is fat within a cystic, often unilocular mass. But, a minority of dermoid cysts will demonstrate no fat or only small foci of fat within the wall or the Rokitansky nodule according to Yamashita et al. On CT, fat-attenuation values are the diagnostic hallmark of a dermoid. In contrast to MRI, bone, teeth, and cyst wall calcifications are reliably detected. Contrast-enhanced MRI or CT can aid in the assessment of complications of teratomas, such as torsion, or malignant degeneration. When no or only small amounts of fat are present, dermoids are difficult to be distinguished from benign cystic ovarian tumours or ovarian cancer, unless a biopsy is performed [4]
The treatment is surgical removal.