Malignant Struma Ovarii: Controversies, Challenges and the Promise of Molecular Diagnosis

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 429-448-Thyroid Neoplasia & Case Reports
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-439
Johnson Thomas*1, Renee Bargman2, David S Rosenthal3, Yuri E Nikiforov4, Wondwossen Gebre5, Paul Liu5, Natalia Martinez-Schlurmann5 and Kenneth Howell Hupart6
1Nassau University Medical Center, East Meadow, NY, 2Nassau University Medical, East Meadow, NY, 3Nassau University Medical Center, E Meadow, NY, 4Univ of Pittsburgh, Pittsburgh, PA, 5Nassau University Medical Center, 6Nassau Univ Med Ctr, East Meadow, NY
Malignant struma ovarii(SO) with metastasis is a very rare disease, only 45 cases have been reported in the medical literature since 1900 with a pooled mortality rate of 15% & a recurrence rate of 22%. Our patient is the youngest reported with metastatic SO; she is also the first reported case of metastatic bilateral SO with elevated CA125.

Case report
In 2008, at age 14, AB was found to have a benign cystic teratoma in the left ovary. In 2010, SO was resected from the contralateral ovary. In 2012, a third surgery revealed numerous omental lesions with a benign thyroid follicular appearance, no nuclear features of papillary carcinoma(PTC) or invasion leading to the diagnosis of "peritoneal strumosis". She returned post-operatively with abdominal pain. CT revealed a left 12X8X11 cm adnexal mass and multiple peritoneal nodules. Debulking surgery was performed and tumor was found in spleen, abdominal wall, urinary bladder and rectum.

Immunohistochemistry was positive for thyroglobulin(TG) and TTF-1. Thyroid function tests were normal, TG=229 ng/ml (2-35), anti-TG Ab were absent and CA125=64 U/ml(<21). No mutations in BRAF, RAS or TP53 were identified.

Thyroidectomy followed by 131I ablation is planned.

SO is uncommon; it is found in 2% of cystic teratomas of which only 5% are malignant. Metastasis from malignant SO is rare. The presence of histological features of PTC have been used to identify malignant potential in SO. When this is absent, cancer is diagnosed by the identification of invasion or by the presence of thyroid follicles in ectopic loci. In recent reports genetic markers of thyroid cancer have been applied in attempts to identify the malignant nature of the tumor.

Controversy exists regarding the malignant nature of "peritoneal strumosis". Some believe that benign thyroid tissue from SO can spread to peritoneum and it should not be considered as malignant; others consider the presence of ectopic thyroid follicular cells to indicate malignancy.

Malignant SO has a significant potential for recurrence and mortality. With the advent of molecular diagnostic tests, there is the possibility that the presence of thyroid cancer associated mutations in SO can lead to the early diagnosis of cancer and impel more aggressive therapy. To date, no molecular markers associated with thyroid cancer have been identified in our patient; further analysis continues. We will review the emerging data concerning the molecular diagnosis of malignant SO.

Nothing to Disclose: JT, RB, DSR, YEN, WG, PL, NM, KHH

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