Clinically aggressive phenotype: A clinicopathological case series of atypical pituitary adenomas

Atypical pituitary adenomas were relatively more malignant lesions defined by WHO criteria. However, not all of them show clinically aggressive behavior. Thus, the current WHO criteria of atypical adenoma didn't seem to be enough to distinguish clinically aggressive adenoma. Therefore, we would like to identify other clinical factors in a cohort of atypical pituitary adenomas to a better identification of clinical aggressiveness.

In order to verify predictors of clinically aggressive phenotype among atypical pituitary adenomas, we retrospectively analyzed the clinical characteristics and therapeutic outcomes of consecutive 49 cases.

Totally, 26 cases were identified as clinically aggressive pituitary adenoma. Clinically aggressive lesions were more likely to be functional (46.2% vs. 17.4%, p = .0388) and be detected in males (65.4% vs. 21.7%, p = .0037). Clinically aggressive adenomas also had higher Ki-67 index [5.0 (5.3)% vs. 4.1 (1.3)%, p = .0011] and presented bigger tumor size [11.83 (11.95) cm³ vs. 5.39 (6.08) cm³, p = .0174]. In multivariate analysis, gender (p = .017), functional status (p = .009) and Ki-67 index (p = .024) were independent predictors of clinical aggressiveness. Further analysis revealed that Ki-67 index of more than 4.45% was associated with worse progression-free survival.

Gender, functional status, tumor size and Ki-67 index ≥4.45% were associated with clinical aggressiveness. A clinicopathological classification of pituitary adenomas may be useful to determine who should be under closer radiological follow-up or followed multimodal treatment strategy.