Early recognition of aggressive pituitary adenomas: a single-centre experience.

Background: Pituitary adenomas are usually considered benign tumours, although some of them can exhibit an aggressive behaviour. Patients with clinically aggressive pituitary adenomas are frequently diagnosed with larger masses, and may present an earlier recurrence (or persistence) after surgery. Our aim was to characterise the clinical, histopathological and radiological features of patients with aggressive pituitary adenoma, in order to correlate their clinical behaviour with the response to treatment plan.

Method: We considered an aggressive pituitary adenoma on the basis of radiological features (size, local invasion), pathological reports (atypical adenoma: MIB-1 >3%, p53 immunoreactivity, increased mitotic activity) and clinical aspects (response to surgery, radiotherapy and medical treatment).

Results: Among our cohort of 582 patients, we considered 102 subjects with aggressive pituitary adenomas (18%, 56 male and 46 female): 14 adrenocorticotrophic hormone (ACTH)-secreting, 18 growth hormone (GH)-secreting, 23 prolactin (PRL)-secreting and 47 non-secreting, with a median follow-up of 5 years. In the whole cohort, 75% of patients with aggressive pituitary adenomas presented invasion of surrounding structure, especially GH-secreting, PRL-secreting and non-secreting. Besides invasion, their remission rate after surgery, radiotherapy or medical treatment was similar, irrespective of hormonal secretion. Surgery was the most performed treatment (overall remission rate of 24%), especially in those patients with ACTH- or GH-secreting adenoma, and 22% of patients were submitted to radiotherapy, with a remission rate of 45% after a median of 3 years. Two consecutive years of medical treatment, in patients with secreting pituitary adenoma, achieved disease control in 41% of them. Considering pathological reports, 24% of cases were defined as atypical adenomas; radiological characteristics, responses to medical treatment and remission rates were similar among patients with typical and atypical adenoma.

Conclusions: We proposed a new and comprehensive definition of aggressive pituitary adenoma, based upon radiological, clinical and pathological features. In a selected cohort of patients, radiological invasion resulted in the most common marker to describe the aggressive behaviour of pituitary adenoma. Surgery, radiotherapy and medical treatment (the latter only in secreting adenoma) achieved disease control in half of the patients with aggressive adenoma, especially surgery in those with ACTH-oma and medical treatment in those with GH- and PRL-secreting adenoma. Nevertheless, radiological, clinical or atypical features did not affect the outcome.