LACTOFERRIN IN THYROID LESIONS - IMMUNOREACTIVITY IN FINE-NEEDLE ASPIRATION BIOPSY SAMPLES

OBJECTIVE: Lactoferrin is an iron-binding protein that has been used f or distinguishing normal from neoplastic conditions in many different tissues. In order to improve evaluation of thyroid lesions, we studied tile lactoferrin immunoreaction in cytologic smears obtained by fine needle aspiration and in biopsy samples from primary neoplasms and fro m adenomatous goiter. STUDY DESIGN: A retrospective study on Foe needl e aspiration cytology samples and corresponding available biopsies fro m thyroid lesions in patients examined at Sao Paulo County Hospital be tween 1982 and 1992, performed in order to evaluate lactoferrin immuno reactivity in morphologically well characterized samples from neoplast ic and nonneoplastic lesions. Immunoperoxidase procedures were perform ed using monospecific polyclonal rabbit antihuman lactoferrin as a pri mary antibody and biotinylated goat antirabbit IgG as a secondary anti body. Amplification was performed with the avidin-biotin-peroxidase co mplex, and the color sign of the positive reactions was developed usin g a diaminobenzidine solution. RESULTS: Lactoferrin was not detected i vr cytologic smears from goiters, whereas only oi-le biopsy rc,ns slig htly positive (1/21, or 4.76%). One smear front adenoma showed low pos itive staining (1/19, or 5.26%), which was The observation that lactof errin present in 4 of 13 biopsies (30.77%) from adenoma. Papillary car cinomas were positive in 19 of 33 smears (57.58%) and in 100% of biops ies, whereas 31.25% (5/16) of follicular carcinoma smears were positiv e for lactoferrin, detected in all the biopsy samples. CONCLUSION: Lac toferrin immunoreactivity tons strongly associated with neoplastic pro liferation and may be used as a useful auxillary marker to distinguish malignant from benign thyroid lesions lit cytologic smears and biopsy samples.