Abstract
BackgroundStruma ovarii (SO) is a rare form of ovarian mature teratoma in which thyroid tissue is the predominant element. Because of its rarity, the differential diagnosis between benign and malignant SO has not been clearly defined. It is believed that malignant transformation of SO has similar molecular features with and its prognosis corresponds to that of malignant tumors originating in the thyroid.Case presentationWe report 35-year-old woman with bilateral ovarian cysts incidentally detected by ultrasound during the first trimester of pregnancy. Four months after delivery of a healthy child without complication she was admitted to the hospital for acute abdominal pain. Laparoscopic left adnexectomy was performed initially in a regional hospital; right cystectomy was done later in a specialized clinic. Intraoperative frozen section and a final pathology revealed that the cyst from the left ovary was composed of mature teratomatous elements, normal thyroid tissue (>50%) and a non-encapsulated focus of follicular variant of papillary thyroid carcinoma (PTC).Normal and cancerous thyroid tissues were tested for BRAF and RAS mutations by direct sequencing, and for RET/PTC rearrangements by RT-PCR/Southern blotting. A KRAS codon 12 mutation, the GGT → GTT transversion, corresponding to the Gly → Val amino acid change was identified in the absence of other genetic alterations commonly found in PTC.ConclusionTo the best of our knowledge, this is the first time this mutation is described in a papillary thyroid carcinoma arising in struma in the ovarii. This finding provides further evidence that even rare mutations specific for PTC may occur in such tumors. Molecular testing may be a useful adjunct to common differential diagnostic methods of thyroid malignancy in SO.
Highlights
Struma ovarii (SO) is a rare form of ovarian mature teratoma in which thyroid tissue is the predominant element
To the best of our knowledge, this is the first time this mutation is described in a papillary thyroid carcinoma arising in struma in the ovarii
Previous case series describe the presence of point mutations in BRAF, NRAS, HRAS, and RET/papillary thyroid carcinoma (PTC) rearrangements but none in the KRAS gene [6,15,16,17]
Summary
Alterations most frequently involve codon 61 of HRAS and NRAS and less frequently codons 12 and 13; mutations of KRAS are very rare in general [21,22,23] In line with these observations, our previous study in Serbian patients detected RAS mutations in 6/218 (2.8%) classical papillary tumors and 5/44 (11.4%) follicular variant PTCs. Most detected mutations were in codon 61 of NRAS (8/11, 72.7%) and 3/11 (17.3%) were in codon 12 of KRAS [13]. No studies have as yet correlated RAS and BRAF mutational status or the presence of RET/PTC rearrangements with clinical behavior in thyroid-type carcinoma arising in SO. We describe an unusual case of KRAS mutation-harboring FV-PTC in a patient with bilateral ovarian teratoma This mutation has not been previously reported in any SO, it is sometimes detected in PTC of the thyroid and in a variety of other tumor types.
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