Abstract
Two cases of pituitary adenoma associated with large cyst formation were described. Ultrastructurally, the cyst lining cells resembled those of Rathke's cleft, whereas the adenoma cells were of the prolactin-secreting type as confirmed by immunocytochemical examinations. In addition, an apparent transition between the cyst lining cells and the adenoma cells was identified. These findings suggest that these cases represent an extremely rare form of adenohypophyseal tumor which has been termed “transitional cell tumor” by Kepes.
