ALPHA-1-ANTICHYMOTRYPSIN IMMUNOREACTIVITY IN PAPILLARY CARCINOMA OF THE THYROID-GLAND

Aim: Papillary thyroid carcinoma (PTC) is the most common malignant tu mour of the thyroid gland. The immunohistochemical profile of PTC is c haracterized by immunoreactivity of tumour cells for cytokeratins, thy roglobulin, vimentin, EMA and S100 protein. Recently, the presence of a serum protease inhibitor, alpha-1-antitrypsin (AlAT), has been demon strated in tumour cells of PTC. The aim of our study was to test immun oreactivity of PTC for another inhibitor of proteases, alpha-1-antichy motrypsin (AlACT). Methods and results: Serial paraffin sections of ni ne consecutive cases of PTC were tested with anti-AlAT and anti-AlACT antibodies. No immunoreactivity for AlAT and AlACT was found in the no rmal thyroid tissue surrounding each tumour. In seven out of nine case s, tumour cells of PTC showed cytoplasmic immunoreactivity for AlACT. In two cases, AlACT was detected even in the nuclei. Immunoreactivity for AlAT was found only in three cases. Two cases of PTC showed no sta ining for both AlACT and AlAT. No significant correlation of AlACT sta ining was found with various prognostic indices (age of patients, hist ological pattern, tumour size, presence of regional lymph node metasta ses). The two cases showing a lack of staining for both AlACT and AlAT showed a more aggressive clinical behaviour. Conclusions: Our prelimi nary study shows that AlACT is expressed by tumour cells in a large pr oportion of papillary carcinomas of the thyroid gland. Its significanc e remains, to the best of our knowledge, still unknown. The observatio n of a more aggressive behaviour in the two cases characterized by the absence of immunoreactivity for both AlACT and AlAT suggests that the presence or absence of protease inhibitors could play a role in contr olling tumour progression in PTC.