Distribution of sialic acid-dependent carbohydrate epitope in thyroid tumors: Immunoreactivity of FB21 in paraffin-embedded tissue sections

The reactivity of monoclonal antibody FB21, which recognizes a sialic acid- dependent carbohydrate epitope, was tested with 94 non-neoplastic and neopl astic thyroid tissue specimens using immunohistochemical methods on formali n-fixed, paraffin-embedded tissue sections. These specimens included 11 cas es of adenomatous goiter, three cases of Basedow's disease, 30 cases of fol licular adenoma, 20 cases of papillary carcinoma, 15 cases of follicular ca rcinoma, six cases of medullary carcinoma, and nine cases of anaplastic car cinoma, FB21 reacted with 14 of 15 cases of follicular carcinoma that showe d a microfollicular or trabecular pattern, and with nine of 20 cases of pap illary carcinoma. A positive reaction was found on the cell surface membran es or apical parts of neoplastic follicles. FB21 also reacted with five of 30 cases of follicular adenoma, These cases showed a follicular pattern and positive staining pattern similar to that in follicular carcinoma. Adenoma tous goiters, Basedow's disease, medullary carcinomas, and anaplastic carci nomas were negative for FB21 reactivity. Although the different reactivitie s of FB21 with papillary carcinoma and follicular carcinoma remain to be in vestigated, the high frequency of reactivity with FB21 suggests that it may be useful as a complement to morphological diagnosis in follicular carcino ma.