Iodine-Negative Rare Gluteal Muscle Metastasis of Papillary Thyroid Cancer: Detected by 68 Ga-DOTATATE PET/MRI and 18 F-FDG PET/CT - Case Report

Sep 29, 2026

Upload by dawugda

A 57-year-old man with metastatic papillary thyroid carcinoma (PTC) to lymph nodes, lung, and mediastinum remained RAI-refractory despite multiple high-dose radioactive iodine treatments, with persistently rising serum thyroglobulin. After the third high-dose therapy, simultaneous 68Ga-DOTATATE PET/MRI and 18F-FDG PET/CT identified a painless mass in the left gluteal region. Excision and histopathology confirmed metastatic PTC. This case highlights rare skeletal muscle involvement and different tumor affinities across 68Ga-DOTATATE PET/MRI, 18F-FDG PET/CT, and whole-body iodine scintigraphy, meeting ATA 2015 criteria for RAI-refractory disease.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages4

Reading Time10 min

AccessFree to download

Abstract

Keywords

Introduction

Case Report

Discussion

Figures and Imaging Findings

Article published online: 2025-06-03 Case Report 383 Iodine-Negative Rare Gluteal Muscle Metastasis of Papillary Thyroid Cancer: Detected by 68 GaDOTATATE PET/MRI and 18 F-FDG PET/CT Seckin Bilgic 1 Irem Koroglu 1 M. Sait Sager2 Kerim Sonmezoglu2 1 Department of Nuclear Medicine, Uludag Medical Faculty, Uludag University, Bursa, Türkiye 2 Department of Nuclear Medicine, Cerrahpasa Medical Faculty, Istanbul University, Cerrahpasa, Istanbul, Türkiye World J Nuclear Med 2025;24:383–386. Address for correspondence Seckin Bilgic, MD, Department of Nuclear Medicine, Uludag University, Uludag Medical Faculty, Gorukle, 16059 Nilufer/Bursa, Türkiye (e-mail: [seckinbilgic@uludag.edu.tr](seckinbilgic@uludag.edu.tr)). Abstract Keywords ► papillary thyroid carcinoma ► gluteal muscles ► RAI-refractory ► 68Ga-DOTATATE PET/MRI ► 18 F-FDG PET/CT The case presents a 57-year-old male with metastatic papillary thyroid carcinoma (PTC) to the lymph nodes, lung, and mediastinum. Despite receiving multiple high-dose radioactive iodine (RAI) therapies, the patient ’s serum thyroglobulin levels continued to rise. The patient, who was unresponsive to RAI therapy, was being evaluated for suitability for 177 Lu-DOTATATE therapy. Therefore, after the third high-dose treatment, simultaneous 68Ga-DOTATATE PET/MRI and 18 F FDG PET/CT imaging were performed, revealing a painless mass in the left gluteal region. The gluteal mass was excised, and histopathology conﬁrmed it as metastatic PTC. Muscle metastases are extremely rare for PTC. This case exempliﬁes the different levels of tumoral afﬁnity shown by aggressive variants of PTC across three distinct imaging modalities: 68Ga-DOTATATE PET/MRI, 18 F FDG PET/CT, and whole-body iodine scintigraphy. Introduction Papillary thyroid carcinoma (PTC) is the most common cancer of the thyroid gland.1 While cervical lymph node metastasis appears more frequently, the rate of distant metastasis is low. Distant metastases frequently occur in the lungs and bones and to a lesser extent in brain and liver tissue.2 In our case, we aimed to present a rare metastasis of PTC to the gluteal muscles.3,4 Case Report A 57-year-old male patient presented with complaints of neck swelling, shortness of breath, and difﬁculty swallowing. During his examinations, an approximately 5cm solid nodule in the left thyroid lobe was found. Fine-needle aspiration biopsy suggested PTC, associated with pathological lymph nodes in the left cervical lymphatic stations. Consequently, he underwent a total thyroidectomy with central neck article published online June 3, 2025 DOI [https://doi.org/](https://doi.org/)[ ](https://doi.org/)10.1055/s-0045-1809423 . ISSN 1450-1147. dissection and left modiﬁed lateral neck dissection. Histopathological examination revealed diffuse sclerosing variant papillary thyroid cancer with a partial tall cell variant in the left lobe, with the largest tumor size being 5cm. After the surgery, serum thyroglobulin (Tg) levels were above 500 ng/mL, suggesting distant metastasis. The patient received high-dose 131I therapy based on the aggressive histological subtype and radiological evidence of distant metastases, as per institutional practice. Radioiodine therapy was administered following recombinant human thyroidstimulating hormone stimulation, in accordance with institutional protocol. Whole-body iodine scintigraphy performed after radioactive iodine (RAI) treatment showed intense increased activity of three foci in the bilateral thyroid beds and multiple masses in the mediastinum and lungs ( ►Fig. 1A, B). RAI therapy with the same dose was repeated three times at 6-month intervals. A 68Ga-DOTATATE PET/MRI (positron emission tomography/magnetic resonance imaging) scan revealed a 7-cm soft tissue mass adjacent to the left © 2025 . The Author(s) . This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestri

FAQs

Why was the patient evaluated for 177Lu-DOTATATE therapy?

The patient showed an unresponsive course to radioactive iodine, with continuously rising serum thyroglobulin despite multiple high-dose RAI treatments.

Which imaging modalities identified the gluteal lesion?

Simultaneous 68Ga-DOTATATE PET/MRI and 18F-FDG PET/CT demonstrated the painless left gluteal mass, while the post-therapy 131I whole-body scintigraphy did not show uptake.

How was the gluteal mass ultimately confirmed?

The mass was surgically excised, and histopathology confirmed metastatic papillary thyroid carcinoma. Immunohistochemistry supported thyroid origin with Tg, TTF-1, and PAX8 positivity.

Sep 29, 2026

Upload by dawugda