Growth hormone-secreting adenoma with lack of retinoblastoma protein expression

Retinoblastoma protein (Rb) is a tumor suppressor whose inactivation causes retinoblastomas, pineoblastomas, and possibly other central nervous system tumors. Although mice with Rb1 gene inactivation invariably develop pituitary adenomas, and some evidence suggests that a subset of pituitary adenomas have lack or reduced expression of Rb protein, to date no evidence has been reported that patients with germline mutations in the RB1 gene (that encodes for Rb protein) are at risk of developing pituitary adenomas. Here, we report the case of a patient with childhood (age 1 year) onset retinoblastoma because of a germline pathogenic variant of the RB1 gene who presented with a somatotropinoma diagnosed at a young age (20) and whose pituitary adenoma cells showed loss of expression of Rb protein by immunohistochemistry, suggesting a role of Rb in preventing the development of pituitary adenomas.