Loss of microsomal antigen in follicular and papillary carcinoma of the thyroid. An immunofluorescence and electron-microscopic study.

All malignant neoplastic cells of papillary carcinoma of the thyroid gland and the majority of follicular carcinoma cells do not demonstrate the presence of normal cytoplasmic microsomal antigen. Follicular adenomas contain cells that demonstrate microsomal antigen, as well as cells that do not. This contrasts with normal and goitrous thyroid glands, which show positive fluorescence of all follicle cells. A concomitant immunofluorescence and ultrastructural study was performed using five normal thyroid specimens, six nodular goiters, five follicular adenomas, four follicular carcinomas, and four papillary carcinomas. The tissues were stained by a sandwich technic with initial incubation with human serum containing high-titer antimicrosomal antibody followed by incubation with fluorescein-conjugated goat antihuman polyspecific serum. The fluorescence findings suggest loss or functional alteration of the normal microsomal antigen in malignant neoplastic cells and some benign neoplastic cells. Ultrastructural study of tissue blocks from the same specimens revealed no conclusive difference in the cytoplasmic organelles of benign and malignant cells. The conclusion is that the immunologic identity of neoplastic follicle cells, as compared with that of normal cells, is altered prior to observable ultrastructural alteration of cytoplasmic constituents.