Struma Ovarii:Hyperthyroithsm in a Postmenopausal Woman

David E. March, Anil G. Desai, Chan H. Park, Pamela J. Hendricks, and Paul S. Davis Department ofRadiology, Department ofRadiation Therapy and Nuclear Medicine, Division ofNuclear Medicine, Department ofRadiology, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania

A rare case of strumaovarliproducinghyperthyroidismin a postmenopausalwomanis reported.Theovariantumordemonstrateduptakeof both[@“Tc]pertechnetateand1311, allowingpreoperativediagnosisof the condition.Infemaleswith unexplainedhyperthyroidism and low 1311uptake by the cervicalthyroidgland,imagingof the pelvisshouldbe considered.

J Nucl Med 29:263—265,1988

enign cystic teratomas comprise ‘@.-10%of all ovar An electrocardiogramshowed atrial fibrillation and flutter ian tumors. Thyroid tissue is found in 1.5—28.5%of with a ventricularresponse of 120—150/mm.To furthereval these and is usually present in small, clinically insignif uate the patient's hyperthyroidism a thyroid scan was per icant quantities. In 1—2%of teratomas, thyroid tissue formed after intravenous administration of 10 mCi of tech is a major constituent of the tumor. Rarely, this tissue netium-99m (@“Tc)pertechnetate. A pinhole image showed a thyroid gland with low tracer uptake (Fig. 1). Twenty-four produces sufficient thyroid hormone to cause hyperthy hour iodine-13l (‘@‘I)uptake was 2.6% (normal 10-35). Be roidism. When either of these features is present, the cause of the patient's known mass, the pelvis was imaged and tumor is designated “strumaovarli―(1). showed tracer activity within the mass, with the bladder It has been reported that 85% ofpatients with struma displaced to the right (Fig. 2). These findings were confirmed ovarii present before menopause and very few proven using ‘31I,and there was persistent 131Jactivity in the pelvis cases occurring after menopause are found in the liter after the bladder was irrigated with saline. ature (2). We report a case of struma ovarii producing A plain radiographof the abdomen revealeda pelvicsoft thyrotoxicosis in an 81-yr-old female. Because the pelvis tissue density containing curvilinear calcifications. Real-time was imaged at the time of radionucide thyroid scan ultrasound showed a mass containing solid and cystic com fling, the diagnosis was made preoperatively. ponents. Computed tomography confirmed the presence of this mass, which measured 15 cm in its greatest diameter and displaced the uterus and bladder to the right. This mass CASE REPORT contained fatty elements and a fat-fluid level was identified (Fig. 3). The computed tomographic appearance was consid An 81-yr-oldfemale presentedwith new onset of supraven ered diagnostic of a teratoma. tricular tachydysrrhythmia. She reported frequent insomnia Themasswassurgicallyremovedandwasfoundto arise and had lost 20 lb. during the year before admission. A history from the left ovary. There were several cysts containing fluid of increased bowel frequency was elicited as well. Physical and sebaceous material. A large solid component consisting examination revealed a blood pressure of 140/95 and an entirely of thyroid tissue accounted for ‘@‘50%of the tumor irregular pulse ofl20/min. The thyroid gland was not enlarged volume and the diagnosis of benign struma ovarii was made. and contained no nodules. A large, firm mass was palpated in One week afterthe surgery,the patient was hypothyroidwith themid-pelvis. a T3 of 26 ng/dl, a T4 of 3.0 @g/d1,and a TSH of 0.2 mIU/ Laboratory investigation was remarkable for a T3 of 200 ml. ng/dl (normal 65—195ng/dl) T4 of 13.7 @g/dl(normal 4.5— A repeat thyroid scan and radioactive iodide uptake were 12.0), and TSH of 0.02 mIU/ml (normal 0.0—6.0mIU/ml). performed 2 mo after the surgery and revealed normal thyroid gland on the scan and a 24-hr uptake of 16% (normal range ReceivedJune 22, 1987;revision accepted Sept. 22, 1987. 10—35%).This is consistent with release from suppressive For reprints contact: Anil G. Desai, MD, Div. of Nuclear effect of the thyroid hormone secreted by the struma ovarii. Medicine, Thomas Jefferson University Hospital, 1lth and Wal Thepatientimprovedsymptomaticallybut theelectrocardi nut Sts., Philadelphia, PA 19107. ogram showed persistent atrial fibrillation.

Volume29 •Number2 •February1988 263 FIGURE2 FIGURE 1 Image of the abdomen taken after [@Tc]pertechnetate [@“Tc]pertechnetatescan showing low thyroid uptake thyroid scanning. There is tracer uptake by a pelvic mass relative to the salivary glands. (arrows) which displaces the bladder (open arrows) to the right. DISCUSSION teratomas. In those cases where the tumor is composed There has been much discussion in the literature entirely of thyroid tissue, it is believed that the terato regarding the precise definition of “strumaovarii.― matous thyroid component has completely overgrown Originally described as an ovarian tumor composed the remainder of the tumor. Earlier suggestions that solely of thyroid tissue, this definition has changed these “pure―cases are due to metastases from the significantly and only 20% of reported cases fulfill this thyroid gland have been discredited (5). criterion (3). One report states that to qualify as true Clinically, most cases of struma ovarii are silent or struma ovarii thyroid tissue should comprise greater present with nonspecific symptoms similar to those than 50% ofthe tumor (4). Most, however, suggest that produced by other benign ovarian tumors. Occasion the thyroid element be a major constituent ofthe mass ally, if the tumor secretes significant thyroid hormone, or that hyperthyroidism result from the ovarian thyroid symptoms and physical findings ofhyperthyroidism are tissue (2, 5, 6). present. Struma ovarn rarely presents with ascites and Most cases of struma ovarii occur within ovarian hydrothorax in a manner similar to Meig's syndrome

FIGURE 3 Computed tomography of the pelvis revealsa large mass (open arrows) with calcificationsand fat-fluidlevel (arrow) displacing the bladder (B) to the right.

264 March,Desai,Parketal The Journalof NuclearMedicine (4), or causes symptoms related to peritoneal adhesions planed low ‘@‘Iuptake by the cervical thyroid that (7). should be evaluated by radionucide imaging of the Struma ovarii is usually diagnosed when pathologic pelvis. examination ofa resected ovarian teratoma incidentally reveals a large component of thyroid tissue. In patients with hyperthyroidism resulting from the tumor, the REFERENCES diagnosis can be made preoperatively because of the 1. Roth LM, Czernobilsky B, eds. Tumors and tumorlike high avidity of the ovarian thyroid tissue for [@mTc] conditions ofthe ovary. New York: Churchill Living pertechnetate and 1311.However, uptake ofthese radio stone, 1985: 85—86. nucides may be misleading because struma ovarii is 2. Fox JF, Clement KW. Functioning struma ovarii. Ann Surg1951;133:253—254. rarely mimicked by functioning thyroid carcinoma me 3. Janovski NA, Paramanandhan TL, (eds). Ovarian tu tastasizing to the ovaries. In addition, concentration of mors. In: Ovarian tumors ofgerm cell origin. Phila 1311 by an ovarian cyst has been reported (8). delphia: W.B. Saunders Company, 1973: 89—90. Histologically, struma ovarii is usually identical to 4. Hurlow RA, Greening WP, Krantz E. Ascites and normal, mature thyroid tissue. The contralateral ovary hydrothorax in association with struma ovarii. Br J Surg1976;63:110—112. contains a benign teratoma in @—5%ofcases. Malignant 5. Fox H. and Langley FA, eds. Tumors ofthe ovary. In: transformation occurs in 5—10%of these patients with Monophyletic Germ Cell Tumours. Chicago: William follicular and papillary carcinoma being the most com Heinemann Medical Books, 1976:236—241. mon histologic types. These tumors have been reported 6. Marcus CC, Marcus SL. Struma ovarii. Am J Obstet Gyn 1961;81:752—761. to metastasize (3). 7. Smith FG. Pathology and physiology ofstruma ovarii. In summary, although struma ovarii is a rare cause Arch Surg 1946; 53:603—626. of hyperthyroidism, there is a subset of female patients 8. Nodine JH, Maldia 0. Pseudostruma ovarii. Obstet with thyrotoxicosis, known pelvic masses, and unex Gynecol1961;17:460—463.

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