Transcription Factor Immunohistochemistry in the Diagnosis of Pituitary Tumors

Objective: The clinical utility and prognostic value of WHO 2017 lineage-based classification of pituitary tumors have not been assessed. This study aimed to (1) To determine the clinical utility of transcription factor analysis for classification of pituitary tumors and (2) To determine the prognostic value of improved lineage-based classification of pituitary tumors. Methods: This was a retrospective evaluation of patients who underwent surgical resection of pituitary tumors at a tertiary referral centre between 1990 and 2016. Included patients were at least 18 years of age and had complete histopathological data, forming the “histological cohort”. Patients with at least 12 months of post-surgical follow up were included in the subgroup “clinical cohort”. The diagnostic efficacy of transcription factor immunohistochemistry in conjunction with hormone immunohistochemistry was compared with hormone immunohistochemistry alone. The prognostic value of identifying “higher risk” histological subtypes was assessed. Results: There were 172 patient tumor samples analyzed in the histological cohort. Of these, there were 96 patients forming the clinical cohort. Subtype diagnosis was changed in 24/172 (14%) of tumors. Within the clinical cohort, there were 21/96 (22%) patients identified with higher risk histological subtype tumors. These were associated with tumor invasiveness (p=0.032), early recurrence (12-24 months, p=0.016), shorter median time to recurrence (38 [IQR 20-68.5] v 15 [IQR 12-27.25] months, p=0.02) and reduced recurrence-free survival (p=0.023). Conclusions: Application of transcription factor analysis, in addition to hormone IHC, is associated with improved diagnostic information.