The role of immunohistochemical examination in diagnosis of papillary thyroid cancer in struma ovarii

Abstract

Introduction. Struma ovarii (SO) is a monodermal teratoma in which thyroid tissue comprises more than 50% of the tumour. Papillary thyroid cancer (PTC) in SO is a rare finding, as only 5% of SO cases undergo malignant transformation. Malignant SO is usually asymptomatic and infrequently diagnosed preoperatively. Because of its rarity, there is no consensus about diagnosis and management, while treatment and follow-up procedures are not clearly established. Material and methods. Herewith, we report two cases of PTC in SO. The first patient was a 25-year-old woman diagnosed with bilateral ovarian tumours. The second patient, 19-year-old woman, presented with unilateral ovarian mass. Both patients were qualified for surgical excision of the tumours. Histopathological specimens underwent both conventional histopathological assessment and immunohistochemical staining. Results. In the first patient histopathology revealed SO with two foci of PTC. Immunohistochemically a positive expression of CK7, CK19, p63 and thyroglobulin (Tg) confirmed the diagnosis. She underwent total thyroidectomy in 2016 in order to enable ablative radioiodine therapy and facilitate further thyroglobulin monitoring. Unfortunately, the patient was lost from follow-up. In the second patient, histopathological diagnosis was follicular variant of PTC in SO. Postoperatively, a pelvic CT revealed osteolytic lesion 6 cm in size, being a metastatic change. The patient underwent unilateral ovariectomy, total thyroidectomy and multiple cycles of radioiodine therapy. Currently, 9 years following the diagnosis, the patient achieved disease remission. Conclusions. PTC in SO still remains a diagnostic and therapeutic challenge. Immunostaining for CK7, CK19, p63 and Tg might be helpful in histopathological diagnosis. The decision on the need of total thyroidectomy and radioiodine therapy should be made individually. However, thyroid remnant ablation increases the sensitivity and specificity of follow-up testing using serum Tg level as a tumour marker.

Malignant Thyroid-type Papillary Neoplasm in Struma Ovarii: A Case Report

“…Germ cell tumors of the ovary are known to arise from any form of pathogenic insult to the normal ovarian germ cell lineage. Such disruption in physiological growth can occur during any stage of ovarian germ cell maturation ultimately leading to neoplastic transformation [1]. Table 2 lists the common genetic mutations leading to PTC in SO.…”

“…The majority of ovarian germ cell tumors are benign, of whom mature teratomas make up 15-20% of the cases [2]. In comparison to its benign counterpart, the incidence of malignant ovarian germ cell tumors is small [1,3]. Teratoma is a subtype of germ cell tumor that arises from one or more of the three germ cell layers.…”

“…SO is a monodermal ovarian teratoma, whose architecture is composed of more than 50% of thyroid tissue [3,6]. It contributes to approximately 2-3% of all ovarian tumors and 2-5% of all ovarian teratomas [1][2][3][4]. The incidence of SO is higher in older adults, although it has also been reported in younger women [7].…”

“…Histologically, papillary and follicular carcinoma of the thyroid is the two most common subtypes of malignancies arising in a SO. Due to the rarity of MSO and its available literature data, no formal standard criteria have been established regarding its diagnosis, management, and follow-up [1,2]. Therefore, the diagnosis of PTC in a SO requires a detailed history followed by a comprehensive clinical examination.…”

“…To date, only about 200 cases have been reported in the literature. It presents more frequently between the ages of 40 and 60 [1]. The majority of SO are benign and belong to the category of mature teratomas, which account for 2-5% of overall benign mature teratomas [2,3].…”