Endocrine Abstracts

Introduction: Topoisomerase II alpha is regarded as the important marker of cellular proliferation. Pituitary tumours are usually benign, but some of them are characterized by rapid growth, high recurrence rate and local invasiveness. Proliferation marker Ki-67 most commonly used in pituitary tumours is not entirely reliable as the indicator of the aggressive growth of the lesion. Topoisomerase II alpha expression assessment may be a valuable tool for identification such pituitary neoplasms.

Aims: The aim of the study was to assess topoisomerase II alpha expression in pituitary tumours as a factor influencing tumour behaviour.

Material and methods: The study included 24 subjects (15 males and 9 females aged 24–79 years, mean age 53 years) who had underwent surgery due to pituitary tumour. The tissue samples were stained immunohistochemically for ACTH, FSH, LH, GH, PRL, TSH and topoisomerase II alpha. Topoisomerase index (IT) was assessed as a number of positive-stained nuclei per 100 tumour cells.

Results: The IT in studied subjects varied from 0 to 93 (median value – 0.8; males – 0.2; females – 0.8). The highest IT value was observed in the case of pituitary germinoma. Among the patients diagnosed with pituitary adenoma, the highest expression of topoisomerase was noted in GH positive- (IT value of 1.35) and ACTH positive tumours (IT of 0.8). The lowest IT values were noted in adenomas co-expressing LH/FSH and PRL/GH (IT of 0.3 and 0.1, respectively). Only in 8% of all studied tumours no expression of topoisomerase was found. The IT in larger tumours invading neighbouring structures was higher but the difference did not reach the statistical significance.

Conclusion: Topoisomerase II alpha seems to be useful marker for assessment of proliferation activity of pituitary tumours, particularly in case of rapidly growing tumours such as germinal neoplasms or metastases. We have presented preliminary results.