Anaplastic thyroid carcinoma with osteoclast-like giant cells.

A case of anaplastic thyroid carcinoma with osteoclast-like giant cells is reported. This is an unusual malignant thyroid neoplasm with morphologic resemblance to giant cell tumor of bone. Light microscopy disclosed an undifferentiated carcinoma. Pleomorphic cells and tumour giant cells were accompanied by numerous osteoclast-like multinucleated giant cells.