Osteoclastic variant of anaplastic thyroid carcinoma: A case report of rare entity.

Anaplastic thyroid carcinoma (ATC) is a rare, highly malignant thyroid tumor with dismal prognosis. Osteoclastic giant cell variant of ATC is extremely rare and is characterized by the presence of a large number of multinucleated giant cells resembling osteoclasts. We report here this unusual variant in a 67-year-old female with a history of long-standing goiter of 13 years duration. Histologically, many multinucleated osteoclast-like giant cells were seen accompanying the malignant spindle cell component. Despite extensive sampling, no evidence of differentiated thyroid malignancy could be elucidated.