Papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC) are types of thyroid malignancy, referred to together as differentiated thyroid cancers (DTC). [1] FTC commonly metastasizes hematogenously to the lungs and bones, while PTC tends to spread to regional lymph nodes.[1,2,3] Metastasis is the most significant prognostic factor affecting survival in DCT We present a rare case of an FTC metastasis to a nodule abutting the left psoas muscle, identified incidentally in a 68-year-old male without thyroidal symptoms while undergoing prostate cancer investigations. PET CT scan revealed increased uptake in the thyroid, for which he underwent a diagnostic thyroidectomy. Histopathological examination of the thyroid revealed a left lobe FTC and right lobe papillary thyroid microcarcinoma

Data was collected through the hospital's online patient records system. A literature search was conducted using the databases '' PubMed'' and ''google scholar'

To our knowledge, this is the first case to describe an FTC metastasis to the retroperitoneum abutting the psoas muscle. Furthermore, patients with known prostate cancer are 30% more likely to be diagnosed with thyroid cancer compared to the general population

This study brings to light a rare case of FTC metastasis to the pelvis on a background of three primary tumours. PET CT is useful to identify the site and source of metastasis, while histcytological assessments are essential for providing a definitive diagnosis.5 Prostate cancer patients are at a significantly increased risk of developing thyroid cancer and active cancer surveillance in those patients is important