18F-FDG PET/CT has been widely validated in recent years for detection and follow-up of differentiated carcinoma of the thyroid and can have a complementary role in patients with high levels of serum thyroglobulin and a negative 131I whole body scan [1, 2] . A 68-year-old woman, who had undergone thyroidectomy 7 years before for papillary carcinoma of the thyroid, came under our observation during follow-up. Serum thyroglobulin was 524 ng/ml (normal <3). A 131I whole body scan showed only a pathological uptake in the left laterocervical region.
An 18F-FDG PET/CT showed two muscular distant lesions, involving the right adductor longus and right iliopsoas muscles. The lesions were confirmed as metastases from papillary carcinoma by biopsy (Fig. 1).
Fig. 1.
18F-FDG PET/CT confirms the presence of the lesion revealed by 131I scan and shows also two muscular distant lesions, involving the right adductor longus muscle (a PET/CT fused transaxial images, b PET transaxial images, c CT transaxial images) and right iliopsoas muscle (d PET/CT fused transaxial images, e PET transaxial images, f CT transaxial images). The lesions were confirmed as metastases from papillary carcinoma by biopsy. To the best of our knowledge, this is also the first described case of a double distant muscle metastasis imaged with 18F-FDG PET/CT
Although extrathyroidal extension to the soft tissues of the neck may occur, distant metastases are rare in patients affected by papillary carcinoma of the thyroid [3]. Skeletal muscle metastases from a differentiated thyroid carcinoma are extremely rare, and only a few cases are reported in the literature [4, 5]. To the best of our knowledge, this is also the first described case of a double distant muscle metastasis imaged with 18F-FDG PET/CT.
Acknowledgments
Conflict of interest
None.
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