Introduction: In 2004, the WHO defined atypical pituitary adenomas (APAs) those with Ki-67 >3%, excessive p53 expression and increased mitotic activity. The usefulness of this classification is still controversial.
Aim: To compare the clinical and prognostic features in a series of typical and atypical pituitary adenomas.
Materials and methods: We retrospectively reviewed 343 consecutive PAs. APAs represented 18.7% of the cases. TPAs represented 81.3% of the cases. All patients were operated on in the Department on Neurosurgery at our institution and followed up in the last 9 years at the Hypothalamic-Pituitary Disease Unit of the same institution. APAs and TPAs did not differ for age at diagnosis, gender, tumor size and extension. ACTH-secreting PAs were more frequent in APAs than TPAS (15.6 vs 6.8%, P=0.02). Radical surgery occurred in 51.5% of APAs and in 71.2% in TPAs (P=0.003). Partial surgery was more likely in APAs than TPAs (OR: 0.43; 95% CI: 0.2470.749). From the 231 patients that underwent radical surgery, recurrence occurred in 42 cases: 7/33 APAs (21.2%) and 35/198 TPAs (17.7%), P>0.05. Disease-free survival time (DFST) did not differ between APAs and TPAs (HR: 1.508; 95% CI: 0.653.497). According to our experience, a Ki-67 value above 1.5% correlated better with partial reception and with a worse DFST. For this reason, we compared recurrence risk and DFST in PAs with KI-67 ≥1.5% and PAs with Ki-67 <1.5%. Among the 232 patients that underwent radical surgery, recurrence occurred in 25% (19/75 cases) of PAs with Ki-67 ≥1.5% and in 14.7% (23/156 cases) of PAs with Ki-67 <1.5% (HR: 2.166; 95% CI: 1.1544.064). PAs with Ki-67 ≥1.5% showed a worse DFST as compared to PAs with Ki-67 <1.5% (HR: 2.166; 95% CI: 1.1544.064).
Conclusion: In our experience, APAs and TPAs did not differ for recurrence and DFST, while PAs with Ki-67 ≥1.5% showed an higher recurrence risk and a worse DFST. We propose that a Ki-67 ≥1.5% may be useful as prognostic marker.