Malignant struma ovarii: A case report

Metastatic malignant struma ovarii to the pituitary presenting as a sellar mass and responding to total thyroidectomy with adjuvant radioactive iodine therapy

Malignant struma ovarii (MSO) is a rare ovarian teratoma composed primarily of thyroid tissue. Common sites of metastasis include peritoneum, bone, liver, lung, gastrointestinal tract and omentum. We present a woman in her 50s with a history of remote oophorectomy presenting with hypopituitarism and a 2.7 cm sellar mass. Trans-sphenoidal surgery for presumed pituitary macroadenoma achieved near total resection and resultant pathology surprisingly showed ectopic thyroid tissue. The patient acquired her ovarian pathology report from Southeast Asia which showed struma ovarii of the left ovary. The pituitary mass was thus determined to be a metastatic lesion from MSO. She underwent total thyroidectomy and radioactive iodine ablation therapy with good initial response and no regrowth of the tissue or emergence of distant metastases after 5 years of annual follow-up. To our knowledge, this is the first reported case of MSO to the pituitary.

Endocrine tumors of the female reproductive tract

Endocrine cells responsible for hormone secretion are found in virtually every organ system. The diverse neoplasms arising from endocrine cells in the female reproductive tract are not well recognized as a distinct component of endocrine oncology. Here, we integrate cellular origins with native anatomical residence to help classify neoplasms of this system. The neoplasms include steroidogenic tumors that arise usually in ovarian stroma, neuroendocrine neoplasms that can arise from normal neuroendocrine cells throughout the female reproductive tract or in ovarian germ cell tumors, and thyroid follicular cell proliferations that are exclusively a component of an ovarian teratoma and may be malignant. The neuroendocrine neoplasms run the full spectrum from indolent neuroendocrine tumors to aggressive poorly differentiated neuroendocrine carcinomas. While many of these lesions are identified as incidental findings in surgically resected tissues, others present with inappropriate hormone excess. An important consideration is the distinction of primary disease from metastatic malignancy. Genetic disorders including those caused by germline mutations of the FOXL2, GNAS, DICER1, STK11 and MEN1 genes can present with primary endocrine neoplasms of the female reproductive tract.

Malignant struma ovarii: From case to analysis

AIM

To evaluate the clinico-pathologic features, treatment options, prognostic factors, and survival outcomes of malignant struma ovarii based on a systematic literature review in association with our case study.

METHODS

A systematic review of the medical literature was performed to identify articles about malignant struma ovarii from January 1983 until July 2020. We evaluated 178 cases.

RESULTS

The 5-year progression-free survival (PFS) and overall survival (OS) of the entire cohort was 72.5% and 91%, respectively. In univariate analysis, younger age (<43 years), whole strumal cyst diameter >95 mm, presence of a histologic type other than papillary classic-type thyroid carcinoma within the tumor and lymphovascular space invasion were related to poor PFS. Patients who received radioactive iodine ablation (RIA) before the treatment failure had significantly higher PFS than those who did not receive RIA (94.9% vs. 64.8%, p = 0.041, respectively). In univariate analysis, PFS was significantly higher in patients who underwent gynecologic surgery followed by thyroidectomy and RIA compared with those who had surgical treatment only (94.5% vs. 64.3%, p = 0.05, respectively). However, this result could not be identified as an independent prognostic factor in multivariate analysis (p = 0.207). Younger age and absence of capsular involvement were related to significantly increased OS. Histologic type was the only independent prognostic factor for PFS (hazard ratio: 3.30, 95% confidence interval: 1.122-9.748; p = 0.030) CONCLUSION: The most common histologic subtype was the papillary classic type. The presence of a histologic type other than the classic papillary thyroid carcinoma within the tumor was an independent adverse prognostic factor.

Metastatic follicular struma ovarii complicating pregnancy: a case report and review of the literature

A 35-year-old woman was determined to have an ovarian cyst and underwent a right ovarian cystectomy at 10 weeks of gestation. A histopathological examination revealed follicular carcinoma arising in a teratoma. No evidence of metastasis was found after delivery. She underwent a total thyroidectomy, followed by radioactive iodine (RAI) therapy. However, her serum thyroglobulin level increased to 1,437 ng/ml (normal range: 0-52 ng/ml) after 10 months. Radioiodine scintigraphy and abdominal computed tomography revealed liver metastasis and peritoneal seeding. She underwent debulking surgery of the liver, right salpinx, and peritoneal seeding nodules. A pathological examination showed metastatic follicular carcinoma with focal poorly differentiated features. Adjuvant RAI therapy was restarted, and her serum thyroglobulin levels returned to normal. In conclusion, metastatic lesions were successfully treated with a combination of debulking surgery and RAI therapy. Close medical follow-up monitoring serum thyroglobulin levels is mandatory in such patients.

Optimal surgical management of well-differentiated thyroid cancer arising in struma ovarii: a series of 4 patients and a review of 53 reported cases

BACKGROUND

Well-differentiated thyroid cancer arising in struma ovarii is rare. The optimal management of this entity remains undefined. Unilateral cystectomy, unilateral salpingo-oophorectomy (USO), or total abdominal hysterectomy with bilateral salpingo-oophorectomy (TAH/BSO), in addition to total thyroidectomy and radioactive iodine (RAI) ablation, have been employed by various groups. We hypothesized that in patients with thyroid cancer arising within struma ovarii, pelvic surgery alone would be sufficient, provided there is no evidence of gross extra-ovarian extension.

METHODS

We review a series of four patients from a single institution and 53 cases from the literature, comparing the extent of treatment and outcomes. Our literature review focused on low-risk patients with struma ovarii confined to the ovary, without evidence of gross extra-ovarian spread or distant metastases. Cumulative recurrence rate was determined by using the Kaplan-Meier method.

RESULTS

We report the treatment of four patients with well-differentiated thyroid cancer arising within struma ovarii. Patients underwent USO, BSO, or TAH/BSO. One patient underwent prophylactic total thyroidectomy in anticipation of RAI treatment, and was found to have a synchronous papillary thyroid carcinoma. All patients clinically remain without evidence of disease at a median follow-up of 9 (range 0.8-13) years. Treatment strategies in 53 cases from a review of the literature varied. The pooled cumulative recurrence rate of 57 cases with struma ovarii confined to the ovary was 7.5% at 25 years.

CONCLUSIONS

Thyroid cancer arising in struma ovarii is rare. Controversy exists regarding the extent of pelvic resection and management of the thyroid gland. In our series of four patients, all patients are alive without evidence of disease, and the 25-year recurrence rate of 57 cases was low (7.5%), despite a variety of approaches to surgical resection and adjuvant treatment. Extensive pelvic surgery and prophylactic total thyroidectomy to facilitate RAI therapy may be reserved for patients with gross extra-ovarian extension or distant metastases.

Typical thyroid-type carcinoma arising in struma ovarii: a report of 4 cases and review of the literature

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.

A case of metastatic struma ovarii treated with 131I therapy: focus on preservation of fertility and selected review of the literature

Struma ovarii is a rare monodermal ovarian teratoma composed predominantly of mature thyroid tissue. We describe herein the case of a 22-year-old woman who underwent a right salpingo-oophorectomy for struma ovarii at the age of 12 years, who was admitted 8 years later with signs and symptoms of a left pelvic tumor. Laparoscopy detected a left ovarian endometriotic cyst and multiple nodules on the pelvic peritoneum, right lateral abdominal wall, diaphragm, vesical plica and liver. The diagnosis was abdominal and pelvic widespread dissemination of recurrent struma ovarii, with features consistent with the follicular variant of papillary thyroid carcinoma. The patient was treated with a combination of conservative surgery and two 131I administrations (cumulative activity of 350 mCi after dosimetric evaluation). Because of the high degree of hormonogenesis shown by the metastases, the first administration was performed following use of recombinant human (rh) thyroid-stimulating hormone (TSH) to reach adequate TSH levels. To avoid the 'stunning effect' and to obtain high-quality scintigraphy, a whole-body scan was performed with 123I after rh-TSH and before the 131I therapy. We also discuss the potential role and the possible benefit of using gonadotropin-releasing hormone analogs and ovarian tissue cryopreservation to preserve fertility in women treated with 131I for pelvic metastases from malignant struma ovarii.

Follicular variant papillary thyroid carcinoma arising in struma ovarii

Struma ovarii is a rare monodermal ovarian teratoma in which thyroid tissue is the predominant or exclusive element. Malignant transformation is known to occur, usually as classical papillary thyroid carcinoma (PTC). However, the recognition of follicular variant PTC raises the possibility of similar malignancy arising in struma ovarii. We examined 13 cases of struma ovarii to determine if these lesions can exhibit histological, immunohistochemical, and/or molecular features of follicular variant PTC. Ten of these had atypical histology, cytologic features of PTC, and all ten showed diffuse positivity for CK19; eight of these were also positive for HMBE-1. Mutational analysis for BRAF identified no V600E mutations. However, seven of the ten cases with features of follicular variant PTC exhibited a rearranged in transformation (RET)/PTC rearrangement by reverse transcriptase polymerase chain reaction (RT-PCR). The three cases considered to be benign based on histologic and cytologic criteria were negative for CK19 and HBME-1 by immunohistochemistry, and had no evidence of BRAF mutation or ret/PTC-1 and ret/PTC-3 rearrangements. These results indicate that follicular variant PTC can occur in struma ovarii and that such lesions exhibit the same morphologic and immunohistochemical profile as follicular variant PTC in thyroid. The application of molecular testing to verify the diagnosis can be valuable, as these lesions may harbor ret/PTC gene rearrangements.