Clavicular Metastasis as an Initial Presentation of Papillary Thyroid Cancer

Abstract

Background: Papillary thyroid cancer (PTC) metastases to the clavicular bone is rare. While the lung is considered the most common site of metastases from thyroid malignancy, osseous metastases, if seen, are usually observed at sites such as humerus, pelvis, radius, and scapula. Clinical Case: A 44-year-old man presented with an enlarging right neck mass for six months after light trauma to that area. Other than mild pain in the described area, the patient reported 20 lbs of weight loss. Initial x-ray revealed a large soft tissue density mass that extended to the midline of the right proximal clavicle. Soft-tissue neck ultrasound noted a 5.4 x 3.6 cm mass extending from the thyroid with findings of increased vascularity and calcification. CT scan of the neck depicted the extension of the mass into the adjacent sternoclavicular junction with osteolysis of the middle third of the clavicle as well as the superior aspect of the sternal body. A fine needle aspiration of the mass revealed thyroid neoplasm with follicular features and positive immunostaining consistent with thyroid carcinoma. Chest CT showed invasion into the right proximal clavicle, tracheal deviation and extension into the mediastinum. The patient underwent a composite resection of the tumor, including a segmental osteotomy of approximately two-thirds of the medial clavicle. Post surgically the patient’s serum calcium was low at 7.9 mg/dL with a concurrently low PTH of 9 pg/mL and a low 25-hydroxyvitamin D of 16.8 ng/mL. Thyroglobulin was markedly high at 15655.0 ng/mL (confirmed on dilution), and thyroglobulin antibody < 1.0 IU/mL. Pathology report confirmed PTC with extra-thyroidal extension and involvement of clavicle (staged pT4a pN0), however margins and lymph nodes were negative for carcinoma with further genomic findings showing positive KRAS mutation. The patient’s post-operative course was complicated by a large expanding left neck hematoma after a fall; he was immediately readmitted with the hematoma subsequently safely evacuated. Levothyroxine has been held at this time with plans for radioactive iodine treatment eight weeks after surgery. Conclusion: Bone metastases from differentiated thyroid cancer is rare, especially clavicular metastasis arising from PTC. Bone scintigraphy, x-ray and fine needle biopsy are some of the widely utilized methods employed in the evaluation of bone metastasis in the setting of thyroid malignancy. The prospect of recovery is generally favorable in cases of bone metastases, however various factors can affect prognosis and long-term outcomes. Reference: Krishnamurthy A. Clavicle metastasis from carcinoma thyroid- an atypical skeletal event and a management dilemma. Indian J Surg Oncol. 2015;6(3):267-270. doi:10.1007/s13193-015-0387-y