Squamous metaplasia with Hashimoto's thyroiditis presenting as a thyroid nodule.

A 59-year-old Japanese female presented a well-limited and movable thyroid nodule. Histologically, the nodule consisted of clusters of squamous cells surrounded by dense connective tissue in Hashimoto's thyroiditis. The squamous cells were well arranged and showed no mitotic figures. We therefore interpreted this nodule as being squamous metaplasia with Hashimoto's thyroiditis rather than squamous carcinoma of the thyroid. There are no previous reports in the literature of nodular formation of squamous metaplasia in the thyroid.