Two Patients with Highly Aggressive Macrofollicular Variant of Papillary Thyroid Carcinoma

Abstract

The macrofollicular variant of papillary thyroid carcinoma (MFV-PTC) is an unusual type of thyroid carcinoma with histological features that can be confused with nodular goiter or follicular adenoma. It generally has a good prognosis and low incidence of metastases. We report two patients with highly aggressive MFV-PTC including bone metastases, one of whom died of their disease. The first patient was a 59-year-old woman with an occipital mass diagnosed histologically as papillary thyroid carcinoma (PTC), follicular variant. There were multiple bone lesions on computed tomography. Ten years earlier a biopsy of a thyroid nodule had been negative for malignant cells. Thyroidectomy showed a 3-cm nodule in the thyroid, diagnosed as MFV-PTC. Iodine 131 whole body scan showed uptake in the skull, ribs, thoracic and lumbar spine, and pelvic bones. The second patient was an 81-year-old man with a history of right thyroid nodule treated by total thyroidectomy with a postoperative diagnosis of adenomatous goiter. Three years later he developed a right shoulder mass, histologically diagnosed as follicular variant of PTC. The original thyroidectomy specimen was reviewed and reclassified as MFV-PTC. The patient developed new bone and lung metastases. Three treatments with (131)I were not effective. He died of metastatic thyroid cancer. To our knowledge these are the first cases of MFV-PTC reported with bone metastasis. Although MFV-PTC usually has a good prognosis these cases highlight the importance of careful histopathological examination for MFV-PTC in thyroidectomy specimens that may appear to be seemingly benign nodular thyroid disease.