Rojekar AV *, Fernandes GC **.
(* Assistant Professor, ** Associate Professor, Department of Pathology, Seth G.S. Medical College and K.E.M. Hospital, Mumbai, India)
Struma ovarii is a very unique and rare form of mature teratoma constituting about 3% of all teratomas. Struma ovarii concurrently occurring with other ovarian epithelial tumors has been rarely reported. Concomitant struma ovarii and serous cystadenoma has been mentioned in only two case reports in the extensively searched medical literature. We report a rare occurrence of coexisting struma ovarii along with a serous cystadenoma in a 55 year old woman.
Struma ovarii is a very rare but most common and specialized form of monodermal teratoma. Boettlin, in 1889, was the first to report and describe this entity, after observing the presence of thyroid follicular tissue in ovary. The term struma ovarii is reserved for only those monodermal teratomas when the proportion of thyroid tissue present must be more than 50% of the overall tissue. [1,2,3] Coexistence of this rare variant with surface epithelial tumors is very rare. To the best of our knowledge only two cases of concomitant struma ovarii and serous cystadenoma have been reported in English literature [4,5]. Here we present a rare case of concomitant cystic struma ovarii with serous cystadenoma.
A 55 year old post menopausal female presented with lower abdominal lump since two months. There was no history of pain or bleeding or any other systemic complaints. On per abdominal examination, there was a mass of 20 - 22 week size in pelvis. Abdomen and pelvic ultrasonography showed right sided cystic ovarian mass possibly ovarian teratoma. Intraoperatively right sided cystic ovarian mass (10 x 8 cm) was found with stretched fallopian tube of the same side. Left sided ovary, fallopian tube and uterus cervix were unremarkable. She underwent total abdominal hysterectomy with bilateral salphingo-ophorectomy.
Gross examination of tumor revealed right sided unilocular ovarian cyst with smooth external surface, which measured 8.5 x 6.5 cm. Cut surface showed multiple cystic nodules ranging from 0.5 to 2.5 cm filled with greenish brown gelatinous material resembling colloid filled thyroid tissue. Approximately 40 % of the cyst wall was smooth, wrinkled and grayish white in color. No areas of papillary projections, solid areas, hairs, bone or cartilage were seen.
Multiple sections from ovarian cyst were studied. The cystic wall with multiple nodules showed predominantly colloid filled follicles of varying sizes (> 50%) lined by benign thyroid follicular epithelium. Sections from the flat wrinkled areas showed a cyst wall of fibro-collagenous tissue lined by low columnar epithelium with morphology of serous cystadenoma. No other element of mature cystic teratoma or any other malignant tissue was recognized.
Figure 1. Multiple colloid filled follicles of varying sizes.
Figure 2. Colloid filled follicles are lined by benign thyroid follicular epithelium.
Figure 3. The cyst wall of fibro-collagenous tissue lined by low columnar epithelium.
Bilateral fallopian tubes, contra-lateral ovary and uterus with cervix showed normal histology. Immunohistochemistry with TTF-1 (Thyroid Transcription Factor – 1) was done and showed strong positivity in follicular epithelium while the areas with appearance of serous cystadenoma were absolutely negative Hence the diagnosis of concomitant cystic struma ovarii with serous cystadenoma has been confirmed.
Figure 4. TTF-1 is negative in follicular lining epithelium.
Very rare occurrence of concomitant struma ovarii with serous cystadenoma has been reported only in two case reports. Struma ovarii is defined as a monodermal highly specialized mature teratoma composed either exclusively or predominantly of thyroid tissue or in which thyroid tissue can be recognized macroscopically. They may have features similar to thyroid adenoma or carcinoma (malignant struma ovarii) or both.[1,2,3]
Struma ovarii accounts for 0.3–1% of all ovarian tumors and for 3 % of all mature teratomas. Approximately 5-15 % of mature cystic teratomas show variable proportion of thyroid tissue; however proportion of thyroid should be more than 50 % to classify it as struma ovarii.[1,2,3] Struma ovarii have also been reported with coexisting non-germinal epithelial tumors such as mucinous cystadenoma, Brenner’s tumor, and serous cystadenofibroma.[6,7]
Struma ovarii is commonly seen in older patients than for those with common mature teratomas. Although these patients may experience variety of symptoms similar to all other ovarian tumors, abdominal pain and a palpable lump are the most common symptoms observed. Rarely vaginal bleeding, ascitis (up to 33% cases) and pseudo Meig's syndrome (< 10 cases) are also reported in the literature. [1,2,8] The patient described in this report presented with abdominal mass which is the most common symptom and was 55 years old.
Macroscopically, typically the tumor is brown or green-brown, predominantly solid and gelatinous. A presence of a green to brown glairy fluid is a clue to the diagnosis.
Cystic struma ovarii is very rare.[1,2,8] Recently Szyfelbein, Young and Scully described a series of 20 cases of cystic struma ovarii. Cystic variety of struma ovarii is extremely rare, which may make its identification difficult. In our case, typical morphology and absence of TTF-1 in lining serous epithelial cells in contrast to positivity in follicular epithelium confirmed the diagnosis.
Till now only two cases have been reported of coexisting struma ovarii with serous cystadenoma in the English literature. In both these cases, it was unilateral and confirmed by IHC. Etiopathogenesis of this pathologic process has not been clear; metaplasia of serous epithelium can be the possible explanation.[4,5]
Usually non-functional struma ovarii may present with symptoms and signs of hyperthyroidism, due to autonomous activation of the thyroid tissue, seen in only 8 % of patients. Struma ovarii may demonstrate all pathologic patterns that are seen in the thyroid, including malignancy in 5 -10% of cases in the form of papillary and follicular carcinoma.[1,2,3,10,11]
Knowledge of these rarely associated coexisting pathologies and extensive thorough sampling of cyst along with IHC is required for the accurate diagnosis in this otherwise benign condition as they are difficult to diagnose before surgical intervention.
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Rojekar AV, Fernandes GC. A Rare Case Report Of Cystic Struma Ovarii With Co-Existing Serous Cystadenoma. JPGO 2015. Volume 3 No. 5. Available from: http://www.jpgo.org/2016/05/a-rare-case-report-of-cystic-struma.html