Double adenomas of the pituitary: transcription factors Pit-1, T-pit, and SF-1 identify cytogenesis and differentiation.

The diagnosis of double adenomas of the pituitary can be very complex and is usually suspected on histological assessment of a specimen and confirmed by immunohistochemical and ultrastructural studies. The most commonly applied technique is currently immunohistochemical staining to localize the six pituitary hormones. Application of this technique may fail to identify double adenomas when hormone immunoreactivity is weak or absent in one or both cell populations. We examined specimens from eight patients diagnosed with double adenomas over a 15-yr period. We tested the ability to detect the difference in the two adenomas in each case using three immunostains for the pituitary transcription factors Pit-1, T-pit, and SF-1. We conclude that immunohistochemical localization of the transcription factors Pit-1, T-pit, and SF-1 accurately detects and classifies the distinct cytodifferentiation of double adenomas of the pituitary.