Selective expression of CD44 cell-adhesion molecule in thyroid papillary carcinoma fine-needle aspirates

Recent descriptions of numerous pitfalls in the cytologic diagnosis of thyroid papillary carcinoma on fine-needle aspiration biopsy specimens have prompted studies of new ancillary diagnostic methods. We evaluated the potential use of immunocytochemical staining of thyroid fine-needle aspiration biopsy specimens for CD44, a glycosylated cartilage link protein associated with extracellular matrix adhesion and lymphocyte homing. Fourteen of 16 (88%) classic, surgically confirmed, thyroid aspiration biopsies stained intensely positive for this marker, whereas 0 of 30 (0%) similarly-processed benign aspirates from colloid nodules showed immunoreactivity for CD44 antigen. From this study, we conclude that most papillary carcinomas of the thyroid express the celladhesion molecule CD44, which may be of clinical value in confirming the diagnosis on borderline fine-needle aspiration specimens. Further study of CD44 expression may prove of significant interest in explaining the unusual mode of spread and clinical course of this disease.