Typical Thyroid-Type Carcinoma Arising in Struma Ovarii: A Report of 4 Cases and Review of the Literature

Abstract

Struma ovarii has elicited considerable interest because of its many unique features since Ludwig Pick first elucidated its relationship to teratoma in the early part of the 20th century. In this article, we report 3 cases of papillary and 1 of follicular thyroid carcinoma; 2 of these cases were associated with mature cystic teratoma. Metastases occurred in 2 patients, and 1 died of neoplasm. In regard to the occurrence of thyroid-type carcinoma in struma ovarii, precise terminology should be used, and the expression malignant struma ovarii was avoided as a diagnostic term. Upon review of the literature, papillary carcinoma and follicular carcinoma are the most frequent types of malignancy to occur in ovarian struma; other forms of thyroid carcinoma occur only rarely. The diagnostic criteria for cases of papillary carcinoma are similar to those described in the cervical thyroid gland and are based primarily on nuclear and architectural features. In reference to follicular carcinoma, invasion into the surrounding ovarian tissue, vascular invasion, or metastasis is evidence of malignancy. Histological malignancy in a struma does not necessarily equate with biological malignancy, and the majority of thyroid-type carcinomas do not spread beyond the ovary. Occasionally, metastases of ovarian struma have an innocuous histological appearance, and such cases are referred to as highly differentiated follicular carcinoma of ovarian origin (HDFCO). Because its histological appearance resembles that of nonneoplastic thyroid, HDFCO characteristically cannot be diagnosed until the neoplasm spreads beyond the ovary. In this article, we apply the term typical thyroid carcinoma to those forms of thyroid malignancy arising in ovarian struma that closely resemble the types described in the cervical thyroid gland to distinguish them from HDFCO. Typical follicular carcinoma is more aggressive than the somewhat more common papillary carcinoma, and HDFCO is the least aggressive of these tumor types. Cases of thyroid-type carcinoma arising in the ovary sometimes lack evidence of preexisting struma. The more aggressive thyroid-type neoplasms can arise in thyroid tissue within a mature cystic teratoma, or they may overgrow and replace the struma. Primary thyroid-type carcinoma must be distinguished from rare instances of ovarian metastases that originate in the cervical thyroid gland and the less differentiated forms from other ovarian neoplasms such as clear cell adenocarcinoma and tumors with an oxyphilic appearance. In the differential diagnosis with other ovarian neoplasms, cases of thyroid-type carcinoma associated with strumal carcinoid should not be diagnosed as malignant strumal carcinoid because the latter diagnosis might lead to suboptimal therapy.

Expression of Benign and Malignant Thyroid Tissue in Ovarian Teratomas and the Importance of Multimodal Management as Illustrated by a BRAF-Positive Follicular Variant of Papillary Thyroid Cancer

“…It is impossible to distinguish benign peritoneal strumosis from metastatic spread of a follicular variant of papillary thyroid cancer (PTC) arising from the ovary, that is, minimal deviation follicular thyroid type carcinoma based on histology (7)(8)(9). Only if this entity exhibits overtly metastatic behavior by spreading to lymph nodes or distant sites can the definitive diagnosis of malignancy be made.…”

Peritoneal dissemination of follicular carcinoma arising from struma ovarii in a pregnant woman

“…It is also expected that follicular carcinoma arising from struma ovarii will have a similar tendency toward developing cervical thyroid cancer. According to Roth et al [10], follicular carcinoma originating from struma ovarii had a 45% dissemination frequency, which was higher than the 19% seen in cases of papillary carcinoma. These authors also noted that the incidence of bone metastasis was 19%, which was also higher than the 4% seen in cases of papillary carcinoma.…”

Papillary type thyroid carcinoma originating in struma ovarii: Case report and review of the literature

“…Joo-Yuen Kim, et al Papillary type thyroid carcinoma originating in struma ovarii 은 폐, 간 그리고 중추 신경계로 전이가 된다고 하였으며 반면, 유듀상 암종은 복강이나 림프절로의 전이가 많다고 보고하였다 [13]. …”