CASE REPORT

Imaging struma ovarii by means of 124I-Na PET/CT

Egesta Lopci1, Paolo Colombo2, Marcello Rodari1, Andrea Lania2, Domenico Vitobello3, Lorenzo Leonardi1, Arturo Chiti1

1Nuclear Medicine Unit, IRCCS Humanitas, Italy

2Department of Endocrinology, IRCCS Humanitas, Italy

3Gynaecology Unit, IRCCS Humanitas, Italy

Correspondence to: Egesta Lopci MD

Nuclear Medicine department, Humanitas Clinical and Research Centre

Via Manzoni, 56 (Rozzano), IT-20089 Milano

Tel.: +39 02 82247542

Fax: +39 02 82246693

E-mail: egesta.lopci@gmail.com, egesta.lopci@cancercenter.humanitas.it

[Received 5 III 2013; Accepted 10 VI 2013]

Abstract

Struma ovarii is a rare form of ovary tumour defined as the presence of ectopic thyroid tissue in the ovarian structures. It usually presents with a benign course, although in some cases carcinoma or other malignant tumours can be found in the context of the ectopic tissue. Herein we report the case of a young patient affected by struma ovarii visualized by means of 124I-Na PET/CT. Thanks to the excellent target-to-background ratio of the tracer and the high resolution of the method, we could well identify the presence of some minimal tumour at the level of the left ovary. To our knowledge, this is the first report of its kind.

KEY words: struma ovarii, 124I-Na, positron emission tomography, PET, PET/CT

Nuclear Med Rev 2013; 16, 2: 95–96

Case report

Struma ovarii is a rare form of ovary tumour, accounting for 1% of the ovarian neoplasia, and defined as the presence of ectopic thyroid tissue in the ovarian structures [1]. It usually presents with a benign course, although in some cases carcinoma or other malignant tumours can be found in the context of the ectopic tissue [2, 3].

Herein we report the case of a young patient affected by struma ovarii, which was incidentally diagnosed during a caesarean deli­very. Our 29 year-old patient had the removal of an ovarian cyst during the delivery and histology showed a well-differentiated papillary carcinoma of thyroid origin. Specific investigations of the thyroid gland, including ultrasound, made the possibility of malignant transformation of the eutopic tissue unlikely, thus suggesting that the degeneration found in the struma ovarii had an in-loco origin (non-metastatic). Before undergoing further treatment [4, 5], we decided to perform a total-body PET/CT scan with 124I-Na (Figure 1).

Figure 1. Maximal Intensity Projection (MIP) image of 124I-Na PET/CT and fused coronal, sagittal and axial sections, showing the ectopic tissue present in the left ovary (arrow); for the study the patient received an I.V. injection of 212 MBq (5.7 mCi) of 124I-Na, and images were acquired 24 hours later (T1/2 4.2days) by means of a 3D PET/CT tomograph (Siemens Biograph 6 LSO: 3.5 min/bed position, 128 × 128 matrix, zoom 1.0, 95 mAs, 130 kV and 5 mm collimation 6 × 3 mm for the localization CT; OSEM iterative algorithm).

Along with the pathologic tracer accumulation, we could also identify some physiologic uptake in the thyroid gland, as well as in the stomach and in the bladder, due to salivary and urinary excretion

Thanks to the excellent target-to-background ratio of the tracer and the high resolution of the method (~0.5 cm), we could well identify the presence of some minimal tumour residue (diameter = 0.6 cm; ki67 ~25%) at the level of the left ovary (arrow). This could not be imaginable with other methods, including total-body 123/131I-Na scan, because of the suboptimal resolution (1.0–1.5 cm) or CT/MR, because of the inadequate specificity.

To our knowledge, this is the first report of its kind, documenting the presence of struma ovarii by means of 124I-Na PET/CT.

References

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