ABSTRACT
Anaplastic thyroid carcinoma (ATC) is a rare, highly malignant thyroid tumor with dismal prognosis. Its usual presentation is in elderly patients as a very rapidly growing mass. ATC mainly shows three patterns: spindle cells, giant cell and squamoid but these three subtypes frequently coexist. 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 are reporting here this unusual variant in a 67-year-old male with a history of progressively increasing midline neck swelling and pulmonary metastasis and left jugular vein thrombosis. Cytologically, many multinucleated osteoclast-like giant cells were seen accompanying the malignant spindle cell component.