Typical morphological characteristics of the immunohistochemical subtypes of pituitary microadenomas: a dual center study.

Purpose: This study aimed to investigate the relationship between magnetic resonance image (MRI) features and the immunohistochemical subtypes of pituitary microadenomas (PMAs) characterized by location and growth pattern.

Materials and methods: A double-center, retrospective review of MRI characteristics was conducted in 57 PMA cases recorded from February 2014 to September 2023, identified based on the 2017 World Health Organization classification of pituitary gland tumors. The geometric center of the tumor was defined, and the possibility of PMA vertical or lateral growth patterns was evaluated according to the ratio of maximum diameter between the X and Y axes.

Results: Among the PMAs, somatotroph adenomas (STAs) significantly frequented the lateral-anteroinferior portion of the pituitary gland (P = 0.036). Lactotroph adenomas (LTAs) showed a significant locational preference for the lateral-posteroinferior portion (P = 0.037), and gonadotroph adenomas (GTAs) were predominantly located in the central-anteroinferior portion (P = 0.022). Furthermore, PMAs in the suprasellar portion exhibited vertical extension with statistical significance (P = 0.0).

Conclusion: In our cohort, micro-STAs were predominantly located in the lateral-anteroinferior portion of the pituitary gland, micro-LTAs in the lateral-posteroinferior portion, and micro-GTAs in the central-anteroinferior portion. The growth pattern of PMAs was highly correlated with their vertical position instead of their immunohistochemical subtypes. Therefore, MRI shows potential in differentiating partial PMA subgroups, especially cases within the silent groups.