Follicular carcinoma originating from struma ovarii: A case report

Follicular carcinoma originating from struma ovarii is a clinically rare low-grade malignant tumor. The pathological diagnosis of ovarian thyroid follicular carcinoma is predominantly based on the infiltrative growth and vascular involvement of tumor cell nests of different sizes in the ovarian parenchyma.

Here we present a case of this malignancy in which the bilateral ovaries, right oviduct wall, myometrial surface, omentum, and bladder reflex were extensively involved Microscopically, the thyroid follicles in this case showed infiltrative growth of nodules of different sizes in the ovarian stroma.

The epithelial layer of the follicles was atypical, but with no nuclear features of papillary thyroid carcinoma such as nuclear groove and nuclear pseudoinclusions. Immunohistochemistry showed positive expression of thyroglobulin, thyroid transcription factor-1, and cytokeratin19, with a Ki-67 index of 5% +. Immunohistochemical results combined with microscopic morphology allowed a diagnosis of follicular carcinoma originating from struma ovarii.

After exclusion of contraindications to surgery, the patient underwent surgical exploration on July 26, 2022, during which frozen pathological examination was performed.

The patient recovered well and was discharged. At the first follow-up visit in October 2022, the patient had an excellent survival.

The analysis of the microscopic morphological characteristics and immunohistochemistry deepened our understanding of the pathological characteristics of ovarian and thyroid follicular carcinoma, and further provides a diagnostic reference for other clinicians who will encounter these conditions in the future.