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INTRODUCTION: Struma ovarii is an ovarian teratoma, represented in more than 50% by thyroid tissue. Five percent of struma ovarii cases have been proven to be malignant and, as in the thyroid gland, papillary thyroid carcinoma is the most common histotype arising in struma ovarii. Because of the unusual occurrence of this tumor, its management and follow-up after pelvic surgery is still controversial. Usually, total thyroidectomy followed by radioiodine treatment is the choice treatment in metastatic malignant struma ovarii, while these procedures are still controversial in non-metastatic thyroid cancer arising in struma ovarii. CASE PRESENTATION: We report a female with follicular variant of papillary thyroid carcinoma arising in struma ovarii. After pelvic surgery, thyroid morphofunctional examinations were performed and a single nodular lesion in the left lobe was discovered. The patient underwent total thyroidectomy and histological examination showed a papillary carcinoma. Radioiodine-ablation of residual thyroid tissue was performed and levothyroxine mildly-suppressive treatment was started. CONCLUSIONS: A more aggressive treatment should not be denied for malignant struma ovarii without any evidence, even when apparently confined into the ovary. However, in selected cases, aggressive treatment may be advisable to decrease the risk of recurrence and to allow an accurate follow-up.
RESUMO
OBJECTIVES: To demonstrate the feasibility of 90Y-PET imaging for biodistribution assessment after selective internal radiotherapy treatments with 90Y-microspheres, comparing the results with 99mTc-macroaggregated albumin (MAA) images obtained with single-photon emission computed tomography. METHODS: Preliminary studies were performed with the aim of evaluating the imaging system spatial resolution and scanner sensitivity for detecting annihilation photons. Subsequently, microsphere distribution was evaluated in 10 patients who underwent liver selective internal radiotherapy treatment. 99mTc-MAA and 90Y-microsphere were simultaneously injected for immediate monitoring after treatment. For each patient, the metastases detected with 90Y-PET and 99mTc-MAA were assessed and compared with 18F-fluorodeoxyglucose-PET (18F-FDG-PET) obtained before treatment and used as an imaging benchmark procedure. The correlation between these techniques was thus investigated in terms of matching lesions. Lesions were considered true positive in the case of matching with 18F-FDG-PET. The sensitivity of both techniques was evaluated as the true-positive fraction of detected spots in the treated liver sectors. RESULTS: With our experimental setup, a maximum scanner sensitivity of 0.577 and 0.077 cps/MBq was obtained for three-dimensional and two-dimensional acquisitions, respectively. A good correlation was obtained between images obtained before and after treatment, with 90Y-PET being by far the most accurate technique in detecting microsphere distribution and tumor nonhomogeneity areas. A sensitivity as high as 0.91 was obtained with 90Y-PET, whereas 99mTc-MAA imaging showed a SE of 0.75. CONCLUSION: 90Y-PET is a promising and reliable technique for microsphere biodistribution evaluation after liver selective internal radiotherapy treatment. Because of the better resolution and the possibility to perform computed tomography fusion, 90Y-PET images are more accurate than 99mTc-MAA single-photon emission computed tomography, which is now considered the gold standard for biodistribution assessment.
