Extramedullary Multiple Myeloma in the Thyroid with Papillary Thyroid Cancer Metastasis to a Parathyroid Gland

Objective: To describe a case of amyloid present in the thyroid gland of a patient with papillary thyroid cancer metastasizing to a parathyroid gland. Methods: We present a case report and review the relevant literature. Results: A 66 year old man with untreated multiple myeloma and subclinical hypothyroidism presents for subclinical hypothyroidism evaluation. He was found to have an abnormal thyroid on physical exam resulting in a thyroid ultrasound being obtained showing a multinodular goiter. Fine needle aspiration of a right thyroid nodule revealed papillary thyroid cancer. Thyroidectomy pathology showed papillary thyroid cancer invading a right inferior parathyroid gland and amyloid in the background thyroid tissue. Due to the presence of amyloid in the thyroid and concern for deterioration in his kidney function, treatment for his multiple myeloma was initiated but the patient expired shortly thereafter from sepsis. Conclusion: Thyroid involvement in multiple myeloma is rare and is a poor prognostic sign. Papillary thyroid cancer metastasizing to the parathyroid gland is also uncommon and its prognosis continues to be debated.