Warthin-like tumor of the thyroid: a papillary carcinoma with mitochondrion-rich cells and abundant lymphoid stroma. A case report.

Papillary carcinoma is the most common form of thyroid carcinoma and, generally, it has a more favorable prognosis than other carcinoma types, although diverse variants or subtypes have been described, some of which appear to have a less favorable prognosis. Recently, a new variant, the so-called "Warthin-like tumor" or "tall-cell variant with extensive lymphocytic infiltration of papillary thyroid carcinoma" with behavior similar to the usual papillary carcinoma, has been described. We present a case with the cytohistological pattern of "Warthin-like tumor" of the thyroid. Immunohistochemistry revealed reactivity at the epithelium lining papillae for antimitochondrial 113-I antibody and also membranous positivity for CD15 (Leu M1). Lymphoid stroma showed an immunoprofile similar to chronic lymphocytic thyroiditis. These findings point to the consideration of "Warthin-like tumor" as being a hybrid neoplasm between the tall-cell variant and oxyphilic papillary carcinoma associated to a lymphoid-rich stroma.