Using 8 different
monoclonal antibodies, immunohistology was performed on 36
follicular adenomas and on 28 follicular, 34 papillary, 27 medullary and 29
anaplastic carcinomas of the thyroid. The panel of
antibodies was directed against broad-spectrum cytokeratins (pan-CK, antibody lu-5), against basic and
acid high-molecular-weight CK of types #1, 5, 10 and 14, against basic (#5 and 6) and
acid high-molecular-weight CK (#13) and against basic (#7 and #8) and
acid low-molecular-weight CK (#19 and #20). With the exception of a large number of
anaplastic carcinomas, nearly all other tumours exhibited strong immunoreactivity with
antibodies against pan-CK, CK 8 and CK 19. CK 20 expression was exclusively shown for 2
medullary carcinomas. Reactivity for high-molecular-weight CK could only, each time focally, be demonstrated for 14 papillary and 2 follicular
carcinomas and for 2
anaplastic carcinomas with partial squamous differentiation. Thirteen
anaplastic carcinomas were not decorated by any of the CK
antibodies applied. CK 7 staining exceeding the staining of individual cells was observed in 26 papillary
cancers. In contrast, such a finding could only be obtained with each one
follicular adenoma,
medullary carcinoma and
anaplastic carcinoma and with 5 follicular
carcinomas. These results confirm earlier studies in that CK 20 expression among thyroid tumours is restricted to the neuroendocrine
medullary carcinomas and that in a larger percentage of
anaplastic thyroid carcinomas an epithelial phenotype can not be demonstrated even upon using broad-spectrum CK
antibodies. New is the finding that there exist considerable differences between
papillary carcinomas and all other non-papillary thyroid tumours regarding CK 7 expression. This result might be of differential diagnostic value for the distinction of follicular and papillary thyroid
neoplasias which sometimes have an overlapping histological pattern.