Mature cystic teratoma with high proportion of solid thyroid tissue: a controversial case with unusual imaging findings

MRI features of ovarian teratomas with somatic-type malignancy and mature cystic teratomas

PURPOSE

We evaluated the magnetic resonance imaging (MRI) features of ovarian teratomas with somatic-type malignancy (TSMs) and benign ovarian mature cystic teratomas (MCTs) to determine the diagnostic contribution of the MRI findings for differentiating these two teratomas.

METHODS

We compared the MRI findings between ovarian TSMs (n = 10) and MCTs (n = 193), and we conducted a receiver operating characteristic (ROC) analysis to determine the MRI findings' contribution to the differentiation of TSMs from MCTs.

RESULTS

The maximum diameters of whole lesion and the largest solid component in the TSMs were larger than those of the MCTs (p = 0.0001 and p < 0.0001, respectively). Fat tissue in solid components was seen in 73/116 (62.9%) MCTs but in none of the TSMs (p = 0.0001). Ring-like enhancement in solid components was seen in 60/116 (51.7%) MCTs and none of the TSMs (p = 0.0031). On dynamic contrast-enhanced MRI (DCE MRI), all of the solid components in the TSMs showed a high- or intermediate-risk time intensity curve (TIC), and those in 113 of the 116 (97.4%) MCTs showed a low-risk TIC (p < 0.0001). The area under the curve of the ROC analysis using the high-/intermediate-risk TIC on DCE MRI was the highest (0.99) for differentiating TSMs from MCTs: sensitivity 100%, specificity 97.4%, positive predictive value 75.0%, negative predictive value 100%, and accuracy, 97.6%.

CONCLUSION

Compared to ovarian MCTs, ovarian TSMs are larger and have larger solid components with high- or intermediate-risk TICs on DCE MRI. Ovarian MCTs frequently show small solid components with fat tissue, ring-like enhancement, and a low-risk TIC on DCE MRI.

Peritonitis From Ruptured Lipid-Poor Dermoid: Struma Ovarii

Mature cystic teratoma (MCT) is a common benign ovarian germ cell tumor. It is more predominantly seen in premenopausal women and contains at least two or more well-differentiated germ cell layers. It is termed a dermoid cyst if the ectodermal tissue is the predominant component. The complications of a dermoid cyst include torsion, malignant degeneration, rupture, and infection. The incidence of a ruptured dermoid cyst is around 1%-2% resulting in chemical aseptic peritonitis from spillage of the cyst contents. Usual clinical presentation is with diffuse abdominal or pelvic pain and abdominal distension. Around 93-96% of dermoid cysts demonstrate fat in the cyst cavity however, minimal or no fat poses diagnostic challenges. In this case, we discuss a rare case of spontaneously ruptured lipid-poor and thyroid tissue-rich left ovarian dermoid presenting with chemical peritonitis. Special magnetic resonance (MR) Imaging sequences such as fat saturation imaging, chemical shift imaging, and gradient-echo imaging assist in detecting scant amounts of fat in the cyst cavity or cyst wall.

Recurrent Struma Ovarii Presented with High Levels of Thyroglobulin

Struma ovarii are rare ovarian tumors, of monodermal germ cell origin, containing predominantly thyroid tissue. They are typically benign unilateral pelvic masses. Among the rare cases of malignancy, the most common histological type is that of the papillary carcinoma. A definite preoperative diagnosis of these tumors is difficult to achieve since most imaging findings are generally nonspecific. A rare exception is the case of synchronous abnormal thyroid blood tests where an ovarian teratoma should be highly suspected, especially when no pathology of the thyroid gland coexists. Surgical excision is the mainstay of treatment. Taking into account that struma ovarii are mainly encountered in patients of a childbearing age, a conservative surgical approach is a reasonable option. We present the case of a 56-year-old woman who was diagnosed with both a primary and recurrent struma ovarii while investigating the incidental finding of elevated blood laboratory levels of the thyroglobulin (Tg).