Distribution of microsomal antigen in various types of thyroid tumour.

Fresh surgical material from forty-eight patients undergoing partial thyroidectomy for thyroid tumour was examined by immunofluorescence staining with antisera for the presence of thyroid-microsomal, mitochondrial and thyroglobulin antigens. Light microscopy on cryostat and paraffin-wax embedded sections was carried out in all cases. Electron microscopy was done on samples from thirteen tumours. Microsomal antigen was present in all normal thyroid tissue, in all eight colloid nodules, in twenty-three out of twenty-four follicular adenomas, in four out of six microangeioinvasive follicular carcinomas, in none of the six papillary, one anaplastic and three medullary carcinomas. Mitochondrial antigen was present in all tumours. Electron microscopy showed marked reduction or absence of microvesicles and other organelles in the papillary and anaplastic carcinomas, thus confirming the suggestion put forward by Goudie & McCallum (1963) that a negative microsomal reaction is associated with dedifferentiation. A negative reaction was also associated with tumours showing advanced oxyphil (Hürthle) cell metaplasia, i.e. total replacement of cytoplasmic organelles by proliferated mitochondria.