[Pituitary carcinomas and aggressive adenomas: an overview and new therapeutic options]

Abstract

Pituitary carcinomas are a rare disease with an estimated prevalence around 0.2 % of the pituitary tumours. They are defined by the presence of intra or extra-cranial metastases but initially they can share the same features as aggressive pituitary adenomas. Indeed there are some indicators that help to differentiate adenomas and carcinomas such as histological findings and immunohistochemical characteristics. Usually in carcinomas, mitotic activity is higher, proliferative index Ki-67 is higher, p53 expression is positive and microvascular density is mostly increased. The majority of carcinomas are prolactin or ACTH-secreting tumors. Dopamine and somatostatin-receptor agonists are not as effective as for the treatment of adenomas. Carcinomas require often repeated surgery and radiotherapy fail to control the tumor. Conventional chemotherapy is poorly effective, but recent case reports with the alkylating agent temozolomide have provided better results at least in the short term. The effects of temozolomide are reversed by the enzyme MGMT and the treatment's response can be predicted by the study of MGMT's expression : tumours lacking MGMT are especially sensitive to temozolomide.