Differentiated Thyroid Carcinoma With Metastatic Presentation: 2 Clinical Cases

Introduction: Papillary thyroid carcinoma is the most common endocrine malignancy. Distant metastasis from differentiated thyroid carcinoma is infrequent, usually seen in lungs and bone. The incidence of bone metastasis is 1%-7% in papillary thyroid carcinoma. Hurtlhe cell carcinoma is a rare malignancy of the thyroid gland that can present with local or distant metastases. Main treatment for metastatic well-differentiated thyroid carcinoma includes radioactive iodine ((131)I) and surgical resection. Clinical case 1: In 2019, a 57 year-old woman, without significant prior medical history, with diffuse upper back and thoracic (10th -12th rib location) pain complaints, for over a year, is submitted to full body bone scintigraphy which reveals a lytic lesion located in the 10th left rib: histology is compatible with metastatic disease, from thyroid follicular carcinoma. Thoracic-abdominal-pelvic computed tomography (CT) has no sign of disease, but thyroid ultrasound shows a left located 24 mm nodule. The patient is submitted to total thyroidectomy and after histology revealed a papillary thyroid carcinoma (follicular variant), (131)I treatment takes place (5550 MBq /150 mCi). Post–treatment(131)I scintigraphy presents with neck foci, in relation with thyroid residual tissue along with intense uptake in a massive lesion around the 10th left rib. Excision of this lesion is decided. The patient remains under clinical and imaging surveillance, being treated with levothyroxine 125 µg and without further complications, until today. Clinical case 2: In 2018, a 78 year-old woman, with prior medical history of hypertension and dyslipidemia, is sent to Neurology practice in the set of diplopia of recent onset. During the evaluation, a thoracic CT reveals a single 4 mm pulmonary lesion and a calcified infracentimetric thyroid nodule. The patient is submitted to bronchofibroscopy and immunohistochemistry of the collected tissue was compatible with metastasis of oncocytic thyroid carcinoma. Thyroid nodule citology is suggestive of Hurthle cell thyroid carcinoma. Total thyroidectomy with central neck lymphadenectomy takes place and histology confirms the diagnosis. After 131I treatment (5550 MBq/150 mCi), 131I scintigraphy reveals 131I uptake foci on the neck, in relation with thyroid residual tissue and a pulmonary uptake focus (known lesion). A second 131I treatment is performed and posterior scintigraphy shows improvement of metastatic disease. The patient remains under clinical and imaging surveillance, being treated with levothyroxine 100 µg and without further complications, until today. Conclusion: These cases reflect the importance of patient complaints in the differential diagnosis, especially osteoarticular complaints, showing that thyroid cancer can present itself already in the metastatic phase and the need to better treat our patients.