Background: Multinucleated giant cells of osteoclastlike appearance are seen in some anaplastic carcinomas, but only three cases in which the diagnosis was made by aspiration cytology are reported in the international medical literature.
Case: A 66-year-old female presented with a history of a palpable neck mass. The diagnosis of fine needle aspiration cytology was anaplastic thyroid carcinoma with osteoclastlike giant cells. Immunohistochemical staining and DNA ploidy analysis were done.
Conclusion: Osteoclastlike giant cells have an origin different from that of the anaplastic component. DNA aneuploidy was noted in our case.