Immunolocalization of pituitary transcription factors.
A. Pituitary specific transcription factor 1 is a nuclear transcription factor that is expressed in all GH/PRL/thyroid stimulating hormone family tumors. In this picture, a densely granulated somatotroph adenoma is illustrated. B. Estrogen receptor alpha (ER‐α) is expressed in PRL‐producing adenomas and gonadotroph adenomas. Of note, the levels of expression tend to be low and if the tissue is poorly fixed, they can be negative. In this picture, a sparsely granulated lactotroph adenoma is illustrated. C. T‐box transcription factor is the corticotroph lineage‐specific pituitary transcription factor. In this picture, a densely granulated corticotroph adenoma is illustrated. D. Depending on fixation time, gonadotroph adenomas may be positive for ER‐α. Among gonadotroph cytodifferentiation markers, steroidogenic factor 1 (SF‐1) is the only gonadotroph lineage‐specific transcription factor in the pituitary gland. This picture illustrates positivity for SF‐1 in a hormone inactive gonadotroph adenoma.