Pituitary adenoma with "honeycomb Golgi" appearance showing a phenotypic change at recurrence from clinically nonfunctioning to typical Cushing disease.

An adenoma resected from a 49-yr-old woman was clinically nonfunctioning but immunopositive for adrenocorticotropic hormone (ACTH) in a few cells. Electron microscopy demonstrated a vacuolar change in Golgi complexes known as "honeycomb Golgi." Recurrent adenoma resected 11 mo later was positive for ACTH in more cells than in the initial one. Two months later the patient presented with typical signs and symptoms of Cushing disease with elevated blood cortisol and ACTH levels and was treated by gamma knife radiotherapy. Among adenomas that are initially clinically silent but became functionally active with recurrence, corticotroph adenomas seem to be the most frequent. Study of transcription factors will be helpful to clarify whether adenomas with honeycomb Golgi represent exclusively gonadotroph adenomas.