Endocrine Abstracts

Background: The 4th edition of World Health Organization (WHO) classification of pituitary tumors recommended evaluation of tumor proliferation and invasion to identify aggressiveness. We aimed to assess the relationship between Ki-67, mitotic index, P53 expression, invasion and recurrence risk in pituitary adenomas.

Methods: Among 601 patients who underwent TN/TS adenomectomy between 2001 and 2016, 101 patients (16.8%) who had tumors with Ki-67 index ≥3 were included and categorized as Group A. The control group (Group B) consisted of 43 patients matched for age, gender and tumor type but had Ki-67 index <3%. Mitotic index and p53 expression were evaluated in 81 tumors. Histopathology reports, pre/postoperative radiological findings, tumor type, recurrence of tumors were assessed retrospectively.

Results: The mean age of patients was 46.9±12.7 years. The most frequent symptoms were visual disturbances (34.7%). Frequency of somatotroph, mammotroph, gonadotroph, ACTH-producing, TSH producing, non-secreting and plurihormonal tumors were 35.4%,20.1%, 16%, 12.5%, 2.8%, 11.8% and 1.4%, respectively. Mean tumor size was greater in Group A compared to Group B (25±10.6 vs 18±11 mm, P<0.01) and frequency of macroadenomas was higher in Group A (67.4% vs 94.1%, P<0.01). Frequency of invasion to adjacent tissue was higher in Group A when compared to Group B (75.8% vs 22%, P<0.01). Fifty-one tumors had invasion to adjacent tissue at MRI and the most frequent invasion site was cavernous sinus (58.8%). The mean follow-up period was 46.6±34 months. One hundred seventeen patients who had postoperative MRI and follow-up data for at least 12 months were evaluated and recurrence risk was higher in Group A patients than Group B (P=0.03). Ki-67 index ≥2.7 was positively associated with recurrence risk. Frequency of recurrence was higher in adenomas with invasion at preoperative MRI (P=0.03). Tumor size and recurrence were not associated with P53 expression. High P53 expression was related with tumor invasion at MRI (P=0.03). Tumors with high (≥2%) mitotic index was more frequent among macroadenomas (P<0.05). Mitotic index was not associated with tumor recurrence risk and invasion. Recurrence risk was higher in tumors with ≥2 histopathological atypia criteria (P=0.01).

Conclusions: High Ki-67 index is a reliable marker for predicting recurrence in pituitary adenomas. Recurrence risk is higher in tumors with two histopathological atypia criteria and invasion.