Imaging diagnosis
Case 151
【Progress】
Unfortunately, we do not have gynecologists in our hospital. She was transported for management to the other municipal hospital where gynecologists were present.
【Discussion】
Teratoma has at least two germ cell layers of the three; exodermal (skin, hair, sweat gland, brain), mesodermal (fat, bone, teeth) and endodermal (mucinous, ciliated epithelium). Teratoma is categorized into three types: mature cystic teratoma (called dermoid cyst), immature teratoma and monodermal teratoma (thyroid tissue called struma ovarii or carcinoid tumor) in which one of the three germ cell layers dominates (1).
On MRI or CT, fat density within a cyst is diagnostic for mature cystic teratoma and immature teratoma includes large solid components with small fats and coarse calcification. Monodermal teratoma includes struma ovarii which is shown like thyroid gland with high signal intensity on T1WI and low signal intensity on T2WI, mimicking hematoma (2, 3).
Mature cystic teratoma is a benign tumor but in the clinical course, we should take care about malignant transformation, torsion, rupture and infection (1, 4-6). It is known that carcinoma can arise in mature cystic teratoma: squamous cell carcinoma most, followed by adenocarcinoma (1). Torsion occurs most in ovarian cyst followed by mature cystic teratoma. The edematous swollen wall of mature cystic teratoma is shown on MRI and/or CT.
The rupture of mature cystic teratoma can occur spontaneously or after trauma such as vehicle accident (1, 6). When it occurs, the fat material can be found in the peritoneum. But no migration of fat material can be found when in case of chemical peritonitis. Chemical peritonitis or in other words, granulomatous peritonitis can occur by the leakage of sebaceous material and bring about retention of intraperitoneal fluid (1, 6). In our case, she did not have traumatic experiences and no fat material was found in the peritoneum but just fluid retention in the peritoneal space on CT. Fluid retention was present markedly surrounding mature cystic teratoma, and present in Douglas fossa and paracolic gutter, indicative of sebaceous leakage from mature cystic teratoma moving into peritoneal spaces.
In case of ruptured mature cystic teratoma, it is reported that fluid level between lipid and fluid the in the cyst is found. Mature cystic teratoma owns a capsule which can be ruptured by trauma, causing hemorrhage. In case of no trauma, digestive enzymes (amylase which dissolves carbohydrates, lipase which dissolves fat or trypsin which dissolves protein) weaken the fragility of the capsule and causes the perforation of the capsule. The leakage of the enzymes, sebaceous component or fat component induces peritonitis (1). In our case, she did not experience accidental trauma and CT showed no evidence of fat component but ascites indicative of coming from chemical peritonitis by leaked digestive enzymes or leaked sebaceous component.
【Summary】
We present a sixty three year-old female suffering from abdominal pain for two weeks. Abdominal palpation revealed the tenderness on the whole abdomen. Abdomen CT showed a mass at the right ovary containing lipid and calcification with fluid level inside. Fluids surrounding the large mass and paracolic gutter and Douglas pouch, indicative of diagnosis as the ruptured mature cystic teratoma (dermoid cyst). It is borne in mind that teratoma has at least two germinal layers of the three ; exodermal, skin component of hair, sweat gland, brain; mesodermal, muscle, lipid, teeth, bone: endodermal, mucinous, ciliated mucous membrane. Ovarian teratoma is categorized into mature cystic teratoma, immature teratoma and monodermal teratoma (struma ovarii, carcinoid tumor). On mature cystic teratoma, three points should be memorized that malignant transformation malignancy (squamous cell carcinoma or adenocarcinoma), torsion and rupture. The rupture of mature cystic teratoma can occur by trauma inducing hemorrhage and occur spontaneously probably because of digestive enzymes such as amylase, lipase and trypsin secreted from the tumor which dissolve the capsule, inducing chemical peritonitis.
【References】
1.Lipson SA, Hricak H. MR imaging of the female pelvis. Radiol Clin North Am 1996; 34:1157-1182
2.Outwater EK, Siegelman ES, Hunt JL. Ovarian teratomas: tumor types and imaging characteristics. Radiographics. 21 (2): 475-90.
3.Fibus TF. Intraperitoneal rupture of a benign cystic ovarian teratoma: findings at CT and MR imaging. AJR Am J Roentgenol. 2000;174 (1): 261-2.
4.Friedman AC, et al. CT of benign cystic teratomas. AJR Am J Roentgenol. 1982;138 (4): 659-65.
5.Buy JN, Ghossain MA, Moss AA et-al. Cystic teratoma of the ovary: CT detection. Radiology. 1989;171 (3): 697-701. Radiology (abstract)
6.Park SB, Kim JK, Kim KR et-al. Imaging findings of complications and unusual manifestations of ovarian teratomas. Radiographics. 2008;28: 969-83
2019.7.3