Cyclin-dependent kinase inhibitor p27Kip1 expression in thyroid cells obtained by fine-needle aspiration biopsy: A preliminary report

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Abstract
Recent studies on paraffin‐embedded tissue have shown that the cyclin‐dependent kinase inhibitor p27Kip1 is expressed in normal thyroid cells, whereas it is downregulated in neoplastic cells. This prospective study was undertaken to assess whether p27Kip1 staining may also be applied to fine‐needle aspiration biopsy (FNAB) samples of the thyroid. We present here our preliminary results on 100 FNABs examined for p27Kip1 expression. p27Kip1 expression was assessed by immunocytochemistry; the technique was optimized on smears prepared from a normal thyreocyte cell line (TL5), which conspicuously expresses p27Kip1, and then applied to FNAB samples prospectively collected from 80 cases of nodular goiter and 20 cases of thyroid neoplasms (10 papillary carcinomas and 10 follicular neoplasms). The TL5 cell culture smears showed that methanol fixation, followed by heat‐induced antigen retrieval, is the most suitable technique for p27Kip1 staining on cytological samples. The FNAB smears similarly treated showed high p27Kip1 expression (75%) in goiter and a significantly lower expression (35%) in neoplasms (P < 0.0001). Our preliminary results show that: 1) p27Kip1 protein expression can be reliably assessed on cytological samples; and 2) p27Kip1 stains nonneoplastic and neoplastic samples in a different fashion, and thus is a useful tool in thyroid cytology. Diagn. Cytopathol. 23:77–81, 2000.