Mature cystic teratoma with torsion

Clinical History

29 years old female came with acute excruciating pain in lower abdomen. There was no associated vomitting or diarrhea or fever. Outside USG revealed mass in right side of lower abdomen and hence patient was referred to us for CT scan.

Imaging Findings

Plain and Post-contrast enhanced MDCT scan of abdomen & pelvis was obtained. The findings were:
A lobulated lesion was seen in the right side of lower abdomen and pelvis, which showed evidence of fat and calcific densities (tooth-like) within. Left adnexa (tube) appeared bulky and thickened and the left ovary was not appreciated separately. Minimal free fluid was seen around this lesion and in perihepatic location.
Uterus was pulled to the right side, however, appeared normal. Normal appearing right ovary was seen separately in the pelvis.

Discussion

Background:

Ovarian teratomas are the most common germ cell neoplasms; most common ovarian tumours in children. Dermoid cysts (better known as mature cystic teratomas) are cystic tumours derived from well-differentiated elements from 2 of the 3 germ layers, namely endoderm, mesoderm and ectoderm.
These are mostly unilocular, filled with sebaceous material with walls lined by squamous epithelium. Various tissues such as hair follicles, skin glands, etc. are contained within the lesion [1].
Dermoid cysts are often complicated by torsion which occurs when the ovary and its vascular pedicle twists around its suspensory ligament. Initially the low pressure of the venous and lymphatic system is compromised causing oedema and engorgement of the mass and later the arterial system fails, leading to thrombosis/infarction [2].

Clinical Perspective:

- Mature cystic teratomas are usually asymptomatic and incidentally discovered with minor complaints such as abdominal pain occurring in a small number of patients.
- When these tumours undergo torsion, the patient may develop excruciating, acute abdominal pain. The condition may mimic pain in acute appendicitis, diverticulitis or renal colic and hence CT proves to be a better modality for diagnosis as compared to USG [2].
- Presence of severe pain in the lower abdomen along with ovarian mass should raise the possibility of torsion. Theses ovarian masses are usually benign, the most common lesion being follicular/corpus luteal cyst and tumour being mature teratoma [2].

Imaging Perspective:

On USG, mature cystic teratoma can have varying appearance, may be seen as cystic lesion with echogenic Rockitansky nodule projecting into cyst cavity, or partially or completely echogenic lesion or multiple thin echogenic bands in cyst [1].
CT scan and MRI confirm the diagnosis, showing fat content of the mass along with calcification, soft tissue and fluid (Fig. 1a, b).

When the lesion undergoes torsion, findings include an enlarged ovary with an underlying mass [Figures 1, 2a, 2b, 3a] and swirling appearing twisted pedicle (Fig. 2c), free fluid (Fig. 3b), uterine deviation to the side of the twist with engorged vessels and fallopian tube thickening on the side of the torsion (Fig. 2c, 3a-c]. Subacute ovarian haematoma with abnormal or absent ovarian enhancement may be seen [2]. Haemorrhagic tube, haemorrhage within the twisted ovarian mass and hemoperitoneum may be seen in torsion with haemorrhagic infarction [3].
Hiller et al [4] noted that misplacement of torsed pelvic structure to midline or to the contralateral side along with uterine deviation to the side of twist (Fig. 2c, 3a, b] are important CT signs of adnexal torsion and were seen in 40 % of cases.

Complications of mature cystic teratoma include torsion (most common), malignant degeneration and rupture [1]. Torsed ovary may result in haemorrhgaic infarction if not treated on time [2].

Though ovarian torsion is rare, radiologists play an important role in early diagnosis.

Differential Diagnosis List

Final Diagnosis

Left ovarian mature cystic teratoma with torsion

URL:	https://www.eurorad.org/case/13630
DOI:	10.1594/EURORAD/CASE.13630
ISSN:	1563-4086