Synchronous Independent Papillary Thyroid Carcinomas in Struma Ovarii and the Thyroid Gland With Different RAS Mutations

Abstract

Struma ovarii is a rare ovarian teratoma predominantly composed of thyroid tissue. The simultaneous presence of thyroid carcinoma in the struma ovarii and the thyroid gland is extremely rare. It remains unclear if these carcinomas represent independent primary tumors and whether the molecular mechanisms of the tumors developing in the thyroid and ovarian tissues are similar. We present the case of a patient with two independent papillary thyroid carcinomas (PTCs) in struma ovarii and the thyroid gland that are driven by different RAS mutations. A 62-year-old woman with a history of chronic lymphocytic leukemia/small lymphocytic lymphoma was diagnosed with a pelvic mass during a CT scan. She had surgery that included removal of her ovaries. A 7.2-cm classical variant of PTC arising in a struma ovarii was identified in the right ovary. Two months after the pelvic surgery, total thyroidectomy was performed, and a small nodule (0.8 cm) in the left lobe was diagnosed as a classical variant of PTC. Molecular analysis of tissues obtained from both the malignant struma ovarii and thyroid gland was performed. RAS mutations both in the PTC located in the thyroid and ovarian tissues were identified. However, whereas the thyroid gland tumor showed an HRAS Q61R mutation, the PTC in struma ovarii harbored an NRAS Q61R mutation. In this case, the finding of distinct types of RAS point mutation in thyroid cancers at two different locations provides definitive evidence that these cancers are synchronously developed independent primary tumors.

Keywords: PTC, RAS; point mutation; struma ovarii; thyroid cancer.

Figure 1.

Hematoxylin and eosin staining of ovary and thyroid tumors. (a) Low-power magnification (×40) showing struma ovarii with PTC in ovary. Normal ovarian tissue is shown in top right field (black arrow). Struma ovarii is bottom right field (blue arrow). (b) PTC in struma ovarii (×400). There is papillary architecture with fibrovascular cores (white arrow). The tumor cells show nuclear enlargement, hyperchromasia, and numerous nuclear grooves (yellow arrow). This tumor harbored an NRAS Q61R mutation. (c) Classic PTC in thyroidectomy specimen (×400). This tumor also shows papillary architecture, nuclear enlargement, hyperchromasia, and nuclear grooves (yellow arrow). This tumor harbored an HRAS Q61R mutation. (d) PTC in thyroidectomy specimen (×400) demonstrating papillae (red arrow).