Endocrine Abstracts

Introduction: Metastatic disease to the thyroid is common due to its rich blood supply, with autopsy series showing prevalence from 1.25% to 24%. The most frequent primary sites include the kidney, lung, breast, head and neck, gastrointestinal tract, and skin. However, non-thyroid malignant tumors are rarely diagnosed clinically and often misinterpreted as primary thyroid tumors, especially in patients with multinodular goiter.

Case presentation: This case involves a patient diagnosed with Clear Cell Renal Cell Carcinoma (ccRCC) of the left kidney at age 40, treated with unilateral nephrectomy and left adrenalectomy. The tumor was graded G1, T2N0Mx. Ten months later, a PET CT scan revealed shoulder blade metastasis, leading to palliative radiation therapy and zoledronic acid administration. A year later, a CT scan identified a mass in the right adrenal gland, confirmed as ccRCC metastasis after right adrenalectomy. Following this procedure, the patient began hormone replacement therapy with mineralocorticoid and glucocorticoid. After ten years (in 2022), a thyroid gland ultrasound revealed a multinodular nontoxic goiter and an 18/15 mm hypoechogenic nodule with microcalcifications in the left lobe of the thyroid gland. A fine needle aspiration (FNA) biopsy was conducted. Cytology was suspicious for either metastasis of ccRCC or papillary thyroid cancer. A total thyroidectomy was performed. Morphology could not differentiate between primary and secondary malignancy, but immunohistochemical staining confirmed ccRCC metastasis. Since then, the patient takes hormone replacement therapy with levothyroxine, without needing thyroid stimulating hormone suppression or thyroglobulin level monitoring.

Conclusion: This case report highlights the importance of careful investigation when identifying nodular goiter in patients with malignancy. Differentiating metastases from primary thyroid cancers is crucial for improving treatment strategies and overall outcomes.