Follicular adenoacanthoma of the thyroid gland

Abstract

A 67 yr old euthyroid black women presented with a painful palpable thyroid nodule. Microscopic examination revealed an extensively infarcted follicular carcinoma with minimal capsular and vascular invasion and advanced squamous metaplasia. From the regions of squamous metaplasia, ultrastructural analysis demonstrated squamous and adenomatous features within the same individual cells. The prognostic importance of histologic distinction between adenoacanthomas and adenosquamous or squamous cell carcinomas is stressed. The literature is reviewed and the etiology, pathology, classification and prognosis of primary thyroid cancers with squamous epithelium are discussed.