Serous Cystadenoma Associated with Cystic Struma Ovarii: A Rare Entity

Introduction

Mature cystic teratomas account for ∼20% of all ovarian tumors. Of these, ∼15% contain normal thyroid tissue. Struma ovarii is a monodermal variant of ovarian teratoma, and predominantly contains thyroid tissue (greater than 50%). The condition was first described by Von Klden in 1895. ¹ It constitutes ∼2.7% of ovarian teratomas ² and typically presents during the reproductive years. The fifth and sixth decades of life are the ages of peak frequency. Struma ovarii rarely occurs before puberty. ³

The vast majority of struma overaii are benign; however, malignant disease is found in a small percentage of cases. ³ The symptoms of this condition are nonspecific and similar to those noted with patients who have other kinds of ovarian tumors. ²

A stroma ovarii is an uncommon type of teratoma; thus it difficult to identify without histopathologic examination. ⁴ Surgical resection remains the definitive treatment for benign disease, and surgery with adjuvant radioiodine therapy has been shown to be successful for treating metastatic and recurrent disease. ³

Case

A 28-year-old female sought medical attention for pain in her right lower abdomen. She reported that her menstural cycles were regular with a normal flow. On abdominal examination, a cystic mass of size 12×8 cm was palpated in the right iliac fossa. A speculum examination revealed that this patient had a normal cervix and a healthy vagina. On vaginal examination, the mass was palpated in her right fornix. Her uterus appeared to be normal in size. Laboratory blood analyses, including a thyroid hormonal profile, showed that her blood parameters were all in a normal range. Ultrasonography a showed cystic mass filled with dense fluid replacing the right ovary. The mass was clearly separated from her other organs, with a thick capsule, and the mass measured 11×7 cm. The patient's uterus, left ovary, and bilateral Fallopian tubes were unremarkable. A clinical diagnosis of a right ovarian cyst was made. The patient underwent an abdominal laparotomy, followed by a right ovarian cystectomy.

Grossly, a grayish-white cystic mass measuring 11×7 cm was received. The mass was cut open and was filled with gelatinous fluid. The wall thickness was variable, varying from 0.3 to 1.2 cm; thus the histologic information conformed to the morphology of the struma ovarii. (Fig. 1. A, B, and C) As seen at one magnification, the wall thickness was 1 mm, measuring 2.5×2 cm, with the histology conforming to the morphology of a serous cystadenoma. (Fig. 1A, area highlighted by arrowhead). Histopathological examination showed that the cyst wall was composed mainly of thyroid tissue in the form of follicles filled with colloid matter; there was no evidence of malignancy (Fig. 2, A and B). Areas of serous cystadenoma were also identified (Fig. 2C). Based on these histopathologic findings, a diagnosis of struma ovarii was made.

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FIG. 1.

Gross images of the patient's cystic ovarian mass of variable thickness varying in diameter from 1 mm (A, arrowhead) to 1.2 cm. (B and C).

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FIG. 2.

Microphotographs of the patients struma ovarii, revealing a cyst wall composed mainly of thyroid tissue (A; H & E 40×) in the form of follicles filled with colloid. (B; H & E 40×). Some areas of serous cystadenoma were also identified (C; H & E 100×).

Results

The patient's postoperative course and her level of thyroid hormones were in normal range after her surgical interventions.

Discussion

The frequency of the occurrence of thyroid tissue in dermoid ovarian cysts range from 5% to 20%. ⁵ A struma ovarii is a teratoma in which thyroid tissue is present exclusively or predominantly. This type of cyst belongs to the group of monodermic and highly specialized teratomas. ⁴ The cyst is generally considered to account for <5% of mature teratomas. ⁶ The age of patients ranges from 6 to 74 years, and the majority of these patients develop this condition the reproductive years. ⁷ Most cases are benign and are usually unilateral.

The symptoms of struma ovarii are similar to those noted in patients with other kinds of ovarian tumors and are nonspecific in nature. These symptoms include abdominal pain, a palpable abdominal mass, abnormal vaginal bleeding, ascites (reported in up to one third of cases), Pseudo-Meigs syndrome (ascites in a hydrothorax; reported in <10 cases). The tumor may present as a large abdominal mass, which can be palpated on examination, depending upon the size and location of the mass. Patients may also experience expanding abdominal growth and a fluid wave that is consistent with ascites. Rarely, dyspnea and pulmonary crackles can be indicative of Pseudo-Meigs syndrome. ³ Thyroid hyperfunction is seen in 5%–8% of patients with struma ovarii. ⁸ If thyrotoxicosis is present, excision of the tumor usually results in regression of this abnormal thyroid function. ⁹

The majority of the patients present only with complaints of abdominal pain and a lump, with an absence of other significant symptoms. Struma overii is usually a benign condition, although occasionally, malignant transformation is observed, ³ which may show cellular atypia and hyperplasia, nuclear pleomorphism, mitotic activity, and invasion into surrounding vessels or the ovarian capsule. ³

Preoperative diagnosis is very difficult because there are different types of teratomas with similar findings. The ultrasonography features of struma ovarii are also nonspecific, but a heterogeneous, predominantly solid mass may be seen. It is difficult to distinguish between struma ovarii and dermoid cysts on the basis of their sonographic appearance. ⁴

Struma ovarii have been rarely described in association with serous cystadenoma. This unusual case of a struma ovarii, presenting with abdominal pain and a lump in association with serous cystadenoma, sheds light on the diagnosis and treatment of this condition.

Conclusions

For the vast majority of cases of struma ovarii, diagnosis is difficult prior to surgical intervention, and surgical resection of the ovary and standard surgical follow-up is sufficient for treating this benign, unilateral disease. ³