Papillary thyroid carcinoma presenting as a solitary soft tissue arm metastasis in an elderly hyperthyroid patient. Case report and review of the literature.

A case of papillary thyroid carcinoma (PTC) presenting as a solitary metastasis in the right arm muscle is described in an elderly hyperthyroid male patient. A 2-cm nodule in the right bycipites muscle was found to be a papillary carcinoma of thyroid origin and a primary, 3.5-cm tumor was subsequently found in the left lobe of a hyperfunctioning gland due to toxic goiter. Both tumors were well differentiated PTC, follicular variant. No high grade features, nor extrathyroidal spread, nor regional lymph node metastases were found, but histology evidenced intrathyroidal vascular invasion. After radical surgery and radioiodine therapy, the patient is currently disease-free 4 years after diagnosis. This is the third reported case of PTC manifesting as a single soft tissue metastasis and the first associated with hyperthyroidism. Hematogenous spread of differentiated PTC is rare, although less unusual in PTC follicular variant. Histological vascular invasion, hypervascularity and increased blood flow in the hyperfunctioning thyroid gland might have facilitated the dissemination of malignant tumor cells through the bloodstream. Literature data indicate that PTC in elderly patients is increasing and is often clinically aggressive. Radical surgical and radiometabolic treatments are required also in this age group to improve clinical outcome.