POU1F1 and neoplasm: According to the new 2022 WHO classification of PitNETs, histological subtypes that can cause acromegaly are densely granulated somatotroph tumours, sparsely granulated somatotroph tumours, mature plurihormonal PIT1, immature PIT1 tumours, mammosomatotroph, acidophil stem cell, and mixed somatotroph and lactotroph tumours (2).