Transcription factor immunohistochemistry in the diagnosis of pituitary tumours

Objective: The clinical utility and prognostic value of WHO 2017 lineage- based classification of pituitary tumours have not been assessed. This study aimed to (1) determine the c linical utility of transcription factor analysis for classification of pituitary tumours and (2) determine the progno stic value of improved lineage-based classification of pituitary tumours. Methods: This was a retrospective evaluation of patients who underwent surgical resection of pituitary tumours at St Vincent's Public and Private Hospitals, Sydney, Australia 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 ide ntifying 'higher-risk' histological subtypes was assessed. Results: There were 171 patient tumour samples analyzed in the histolog ical cohort. Of these, there were 95 patients forming the clinical cohort. Subtype diagnosis was changed in 2 0/171 (12%) of tumours. Within the clinical cohort, there were 21/95 (22%) patients identified with higher-risk hist ological subtype tumours. These were associated with tumour invasiveness (P = 0.050), early recurrence (12-24 months, P = 0.013), shorter median time to recurrence (49 (IQR: 22.5-73.0) vs 15 (IQR: 12.0-25.0) months, P = 0.005) and reduced recurrence-free survival (P = 0.031). Conclusions: Application of transcription factor analysis, in addition to h ormone immunohistochemistry, allows for refined pituitary tumour classification and may facilitate an imp roved approach to prognostication.