Endocrine Abstracts

Aggressive pituitary tumors are classically defined as pituitary tumors with large size, rapid growth and massive invasion of surrounding anatomical structures. This is a group of pituitary tumors with biological behavior between pituitary adenomas and carcinomas and includes a new group of pituitary tumor, defined atypical adenoma, characterized by the presence of invasive growth and combination of increased mitotic activity and a Ki-67 labeling index >3%. The aim of this retrospective study was to evaluate the epidemiology, histophatological characteristic, including tumor subtype and invasion of surrounding anatomical structures, and clinical characteristics of aggressive pituitary tumors, defined on the basis of a Ki-67 labeling index >3%. The analysis was performed in a cohort of 308 patients who underwent neurosurgery for pituitary tumor between 2007 and 2011. Twenty-three patients (14 women, 9 men, aged 17–62 years, mean 40 years) were classified as patients with an aggressive pituitary tumors (prevalence=7.5%). The Ki-67 labeling index ranged from 4 to 23% with a mean of 6.9%. Among this group of tumors, 21 (91.3%) were macroadenomas. Moreover, five (21.7%) of the aggressive pituitary tumors and 21 with pituitary adenoma (7.3%) had evidence of invasion of the surrounding anatomical structures (χ²=5.69, P=0.01). Twelve patients (52.1%) had hormone-secreting and eleven had nonfunctional pituitary tumors (47.8%). At the immunohistochemical analysis the tumor subtype were: eight (34.7%) null-cell tumors, six (26%) PRL-secreting tumors, four (17.3%) GH-secreting tumors, three (13%) ACTH-secreting tumors and two silent FSH–LH tumors (8.6%). Based on available post-operative data, 11 out of 18 (47.8%) patients with aggressive pituitary tumors and 29 out of 130 (22.3%) patients with pituitary adenoma had evidence of recurrence (χ²=12.07, P=0.001). In conclusion, aggressive pituitary tumors, evaluated on the basis of Ki-67, were identified in 7.5% of patients underwent neurosurgery for pituitary tumors.These tumors are mainly nonfunctional macroadenomas. The evidence of a higher rate of tumor invasiveness and recurrence suggest the Ki-67 labeling index can be considered a reliable method to individuate an aggressive pituitary tumor.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.