Two patients with highly aggressive macrofollicular variant of papillary thyroid carcinoma.

BACKGROUND: 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.

SUMMARY: 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.

CONCLUSIONS: 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.