Both invasiveness and proliferation criteria predict recurrence of non-functioning pituitary macroadenomas after surgery

Introduction: Additional robust criteria to predict early postoperative recurrence of non-functioning pituitary macroadenomas (NFMAs) are needed. Recently, a new classification of pituitary tumors has been proposed, which is based on both radiological and histological criteria and allows the grading into 5 groups of different potential aggressiveness. The aim of this study was to use this classification to further characterize predictive factors of recurrence in an independent series of NFMA. Cases and methods: 120 patients operated for a NFMA were analyzed retrospectively. For each of them, the invasion of the cavernous and/or sphenoidal sinuses by the tumor was studied on the preoperative MRI and the proliferative character was based on precise histological and immunohistological examination. Results: 26% (n=31) of the adenomas were proliferative and 57% (n=68) were invasive. The invasive lesions were larger (P<0.001) and their removal was complete in only 82% of the cases. The distribution of NFMAs was as follows: 32% grade 1a, 11% (proliferative) grade 1b, 42% (invasive) grade 2a and 15% (proliferative and invasive) grade 2b. Their probability of recurrence at 5 years was 20, 39, 44 and 66%, respectively. A young age, the atypical character and the presence of postoperative residual tumor were all independent risk factors of recurrence (P<0.025). Discussion: The new clinicopathological classification proves to be very useful in predicting the risk of recurrence of non-functioning pituitary macroadenomas after a first surgery. In particular, grade 2b lesions showed an overall likelihood of recurrence that was 8.6 times greater than those of grade 1a.