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Pathology – Research and Practice 201 (2005) 409–412

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TEACHING CASE

Malignant struma ovarii: A case report

F. Bolata,�, S. Erkanlib, F. Kayaselcuka, E. Aslanb, I. Tuncera

aDepartment of Pathology, Bas-kent University Faculty of Medicine, Adana Teaching and Medical Research Center, Adana, TurkeybDepartment of Gynecology and Obstetric, Bas-kent University Faculty of Medicine, Adana Teaching and Medical Research Center,

Adana, Turkey

Received 28 January 2005; accepted 13 April 2005

Abstract

Malignant struma ovarii is a rare form of the ovarian germ cell tumors. Hence, diagnosis and management ofmalignant struma ovarii have not been clearly defined. We present the case of a 34-year-old woman with papillarycarcinoma arising in struma ovarii. The malignant component of this tumor was detected after laparoscopic removal,and a re-staging operation was performed afterwards. There was no evidence of clinical malignancy or metastases.In this paper, clinical features, treatment guidelines, diagnostic features, and immunohistochemical characteristics of

this tumor are reviewed.r 2005 Elsevier GmbH. All rights reserved.

Keywords: Malignant struma ovarii; Ovarian teratoma; Papillary thyroid carcinoma

Introduction

Germ cell tumors constitute 15–20% of all ovariantumors. The majority of them are mature cysticteratomas [3,4,6]. Benign thyroid tissue is observed in5–15% of mature ovarian teratomas. When thyroidtissue comprises more than 50% of the teratoma, it istermed ‘‘struma ovarii’’ [4,10]. Struma ovarii accountsfor only 2% of all mature teratomas, and malignanttransformation has been reported in fewer than 5% ofall struma ovarii [3,4,6,8]. Owing to its rarity, there hasbeen some controversy about the diagnosis and treat-ment, and prognosis is difficult to evaluate [3,4,6–10,14].We present a case of malignant struma ovarii along withits immunohistochemical characteristics. The clinico-

e front matter r 2005 Elsevier GmbH. All rights reserved.

p.2005.04.004

ng author. Bas-kent Universitesi, Patoloji A.D., Adana

gir 01250, Adana, Turkey. Tel.:+90 322 327 2727;

7 1276.

ss: drfilizbolat@yahoo.com (F. Bolat).

pathologic features, differential diagnosis, and manage-ment of this tumor are discussed.

Case report

A 34-year-old woman, gravida 2 para 2, affected byoligomenorrhea and a pelvic mass, presented at ourhospital. Physical examination and pelvic ultrasonogra-phy of the patient revealed a mobile, semisolid, andisoechoic mass (3� 3.1 cm) on the right ovary. The dataobtained by routine blood, urine, and thyroid functiontests, as well as tumor markers, were in the normalrange. The patient did not show any sign of hyperthyr-oidism. A dermoid cyst or endometrioma was presumedin the differential diagnosis. The patient underwentlaparoscopic surgery. At exploration, the left ovary, theleft fallopian tube, and the uterus were normal. Theright ovary was enlarged, and a benign looking whiteand smooth ovarian cystic mass was noted. Right

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Fig. 3. Nuclear staining of TTF-1 was observed in the tumor

cells (immunohistochemistry � 100).

F. Bolat et al. / Pathology – Research and Practice 201 (2005) 409–412410

ovarian cystectomy was done. Dissection of the cyst wallwas slightly more difficult than usual. Owing to ruptureof the cystic mass during dissection, copious irrigationwith sterile water was carried out.On macroscopic examination of the specimen, an

encapsulated cystic mass measuring 4� 4� 3 cm wasobserved. Multiple papillary areas and focal gelatinous,glossy yellow solid areas were seen on the cut section ofthe mass. Histopathologic examination of the glossyparts of the tumor showed the characteristic appearanceof nodular goiter with colloid-filled follicles varying insize and intervening fibrous collagenous stroma. Thepapillary areas on the cut surface of the mass containedpapillae with fibrovascular cores covered by polygonal,clear atypical epithelial cells. The tumor cells showedround to oval, overlapping nuclei with ground-glassappearance; grooves or inclusions could be detected insome of the nuclei (Fig. 1). The tumor was restrictedwithin the capsule, and vascular invasion or mitotic

Fig. 1. Well-differentiated papillary carcinoma arising in

struma ovarii (H&E � 100).

Fig. 2. Cytoplasmic thyroglobulin reactivity of the tumor cells

(immunohistochemistry � 200).

Fig. 4. Papillary processes are lined by a single epithelial layer

with a dense fibrous stroma (H&E � 100).

activity was not identified. Immunohistochemically,tumor cells were strongly positive for thyroglobulin(Fig. 2), thyroid transcription factor-1 (TTF-1)(Fig. 3),and were negative for chromogranin A. Thus, morpho-logic and immunohistochemical findings were concor-dant with a papillary carcinoma arising in struma ovarii.The remaining cyst showed a serous cystadenofibroma(Fig. 4).The patient was informed about the diagnosis of

malignant struma ovarii, the necessary re-stagingprocedure, and the prognosis of her disease process. Inaccordance with the patient’s wishes, fertility-sparingsurgery was planned. A complete examination of thethyroid function and thyroid sonography were carriedout to exclude the low possibility of a primary thyroidtumor. The results were found to be in the normal range.Laparatomy was performed when abdominal explora-tion revealed a nodule not larger than 0.5� 0.5 cm onthe left ovary. After peritoneal washings, a rightsalphingo-oophorectomy, a left ovarian wedge biopsy,an infracolic omentectomy, and a bilateral pelvic andpara-aortic lymph node dissection were performed.

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The definitive histology was negative, and no metas-tases were detected in the regional lymph nodes. Thepatient was found to be affected by stage IC (intra-operative rupture) malignant struma ovarii, and noother treatment was considered. The postoperativecourse was uncomplicated; the patient was dischargedfrom the hospital on postoperative day 7. The patientdid not receive any postoperative adjuvant treatmentand is free of disease 7 months after surgery. She is stillclosely followed up, undergoing clinical, radiologic, andlaboratory examinations every 3 months.

Discussion

Struma ovarii is a monodermal teratoma in whichthyroid tissue is the predominant component of a morecomplex teratoma. These tumors may demonstrate allthe pathologic features observed in the thyroidgland and represent less than 3% of all ovarianteratomas [12]. Owing to the absence of uniformdiagnostic criteria and the rarity of the disease, it isdifficult to assess the incidence of malignant transforma-tion in struma ovarii [3,4,6–10,12,14]. Malignantstruma ovarii mostly occurs in the fifth decade of lifeand is higher in frequency than struma ovarii in general[8,12]. The tumors arise more frequently in the left thanin the right ovary. This is in contrast to our case, inwhich the tumor arose on the right side. Only 6% ofmalignant struma ovarii are bilateral. Only 8% of thepatients with malignant struma ovarii present withclinical hyperthyroidism [3,8,12]. In our case, thyroidfunction tests revealed data that were within the normallimits.Malignancy in struma ovarii is represented by

follicular carcinoma, papillary carcinoma, or a mixedpattern, similar to the types of thyroid carcinoma[3,4,6,10,12]. The histologic criteria for malignancy instruma ovarii are controversial. Malignancy criteriainclude increased cellularity and cellular atypia. How-ever, others argue that the most reliable criterion is thepresence of capsular and blood vessel invasion ordissemination [2,5,11,13]. The absence of capsular andvascular invasion suggests a better prognosis [2].Unfortunately, these may be hard to identify [5]. Thecriteria for malignancy have been reviewed by Devaneyet al. [4], and the presence of malignant nuclear featuresdesignated as ground-glass overlapping nuclei andnuclear grooves have been accepted as the most crucialcriteria for papillary carcinoma. The presence ofvascular and capsular invasion supports the diagnosis.In our case, the malignant component consisted oftypical well-differentiated papillary carcinoma of thethyroid, in which the presence of thyroglobulin andTTF-1 was demonstrated immunohistochemically.

The differential diagnosis of struma ovarii includesthe follicular type of granulosa cell tumor, carcinoidtumor, papillary cystadenoma, and papillary cystade-nocarcinoma [6]. Immunohistochemical stains for thyr-oglobulin and chromogranin A are necessary for thedifferential diagnosis. Exclusion of primary lesions ofthe cervical thyroid is important, because metastaticthyroid carcinoma to the ovary might resemble primarymalignant struma ovarii histologically. This is particu-lary important for lesions consisting of thyroid tissuealone and lacking an accompanying teratomatouscomponent [4].Malignant struma ovarii appears to have a good

prognosis. Among the 13 patients with malignantstruma ovarii, Devaney et al. [4] reported only onepatient with metastatic disease. Among eight patientsadequately followed-up, death did not occur at amedian follow-up of 7.3 years. However, cases showingmetastasis at presentation or during follow-up havebeen reported in the literature [11,14]. The meta-static potential is low in patients with malignantstruma ovarii, but when metastases do occur, the mostcommon sites involved include other pelvic structures,contralateral ovary, omentum, and mesentery orhematogenous spread to the liver, lungs, bone, andbrain [3,6].The preoperative diagnosis of struma ovarii may be

possible through thyroglobulin measurement or scan-ning in patients affected by hyperthyroidism, but themajority of patients are diagnosed postoperatively.Because of the rarity of such cases and the difficultiesrelated to preoperative diagnosis, the management ofmalignant struma ovarii has not yet been clearly defined.Some authors have suggested a management as used forother germ cell tumors [1]. Others have proposed thatmalignant struma ovarii should be treated like itsthyroid counterpart [6]. For women of childbearingage, conservative management may be an option,although there is no sufficient data available. Aftercompletion of childbearing, treatment should consist oftotal abdominal hysterectomy, bilateral salphingo-oo-phorectomy, and staging in the usual fashion[3,4,6,9,14]. After the diagnosis of malignant strumaovarii, a variety of postoperative treatments were used[3]; however, in the literature, most patients did notundergo adjuvant therapy following initial surgery [4].Functioning metastatic sites have been demonstrated byadministration of radioiodine. Thyroidectomy andablation with 131I are necessary for treating advanceddiseases [3]. Iodine scans and thyroglobulin measure-ments are needed for follow-up and recurrence detec-tion. As our patient did not show any clinical orhistologic evidence of metastatic disease after compre-hensive staging, we did not give her any adjuvanttreatment, and she is disease-free after 7 months ofpostoperative follow-up.

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In conclusion, malignant struma ovarii is a medicalrarity. The paucity of published cases makes it difficultfor a physican to discern the natural progression ofdisease and its best treatment modality. When thedissection of a seemingly benign teratoma is harder thanusual, malignancy should be considered; in such cases,frozen sections may be of value for making the correctdiagnosis intraoperatively.

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