Failure of clinical remission after transsphenoidal removal of a microadenoma in a patient with Cushing's disease: multiple hyperplastic and adenomatous cell nets in surrounding pituitary tissue.

A patient with Cushing's disease is described who underwent transsphenoidal adenomectomy of a basophilic microadenoma with a diameter of 3 mm. In a piece of surrounding normal pituitary tissue removed at operation, multiple small nests of adenomatous basophilic cells were found both in the adeno- and neurohypophysis. No clinical improvement was observed. Cortisol secretory rate, plasma ACTH, the absent response of plasma cortisol to insulin-induced hypoglycemia, and the responses of plasma cortisol to lysine vasopressin and TRH remained unchanged. The observations in this patient point to the presence of multiple ACTH-secreting adenomatous cell nests and microadenomas throughout pituitary gland and bring back into view the concept of primary stimulation of hypothalamic corticotropin-releasing factor as the primary derangement in some patients with Cushing's disease.