PREFERENTIAL EXPRESSION OF THE CELL-ADHESION MOLECULE CD44 IN PAPILLARY THYROID-CARCINOMA

CD44 is a polymorphic family of immunologically related integral membr ane glycoproteins associated with cell matrix adhesion, lymphocyte act ivation and targeting, and tumor growth and metastasis. We studied CD4 4 expression in 114 formalin-fixed paraffin-embedded thyroid tumors us ing the A3D8 anti-human CD44 monoclonal antibody. Sixty-five of 67 pap illary carcinomas (97%) strongly expressed CD44 with an intense plasma membrane pattern. Thirty-seven of these cases originated from Albany, New York, and 30 cases from Russia. Immunoreactivity was also observe d in 9 of 16 follicular adenomas (56%); 4 of 8 Hurthle cell neoplasms (50%); 5 of 15 medullary carcinomas (33%); and 3 of 8 follicular carci nomas (38%). These results show that among thyroid neoplasms, papillar y carcinomas preferentially display tile CD44 antigen (P less than or equal to 0.001). Nonneoplastic follicular epithelium exhibited a low t o moderate level of staining. To further characterize the CD44 isoform , we tested a subset of cases with the 2F10 anti-human CD44 variant 6 monoclonal antibody, which recognizes a CD44 variant exon (CD44v6) imp licated in tumor metastasis. Eleven of 11 papillary carcinomas tested were 2F10 positive, and 1 of the follicular carcinomas was positive. T hese results suggest the hypothesis that deregulated CD44v6 expression on the plasma membrane of papillary carcinoma cells contributes to th e ability of those cells to metastasize to regional lymph nodes and th en to remain dormant for years. Our results suggest that human papilla ry thyroid cancer will be an interesting model in which to further stu dy the role of CD44 isoforms, particularly those containing CD44v6, in tumor metastasis and lymphatic invasion. (C) 1994 Academic Press, Inc .