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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.

E-cadherin (E-CD) is a cell-adhesion molecule that has been associated with invasion and metastasis in a wide variety of human neoplasms. We have recently shown that, although decreased E-CD expression is associated with increased bladder-wall invasion and higher tumor grade of infiltrating transitional cell carcinomas (TCC), E-CD expression in the exophytic portion of pure papillary and papillary-infiltrating TCC is increased over that of normal transitional cells. To evaluate whether E-CD levels could serve as a diagnostic adjunct in urinary cytology specimens, we stained 40 alcohol-fixed bladder-washing cytospin preparations with an avidin-biotin-peroxidase method using a monoclonal antibody to E-CD (Sigma Chemical Co., St. Louis, MO). E-CD expression level was defined as a high-intensity or low-intensity staining increase over background squamous cell staining for the transitional cells in 21 biopsy-proven transitional cell carcinomas with papillary components, and in 19 benign or reactive control specimens. Twenty-one of 21 TCC (100%) showed an increased E-CD level over background, with 13 low-intensity and 8 highintensity cases. Ten of 19 benign cases (53%) showed increased E-CD staining over background, with 8 low-intensity and 2 highintensity cases. This difference between malignant and benign specimens was statistically significant (chi-square test. P approximately 0.001). We conclude that increased E-CD expression in the papillary components of TCC can be identified in urinary cytology specimens, may reflect the physical and chemical structural makeup of papillary architecture, and warrants further study as a diagnostic adjunct in the interpretation of urine cytology specimens.