Clinicopathological predictive factors in the early remission of corticotroph pituitary macroadenomas in a tertiary referral centre

Objective: Corticotroph macroadenomas are a rare cause of Cushing's disease (CD), but their properties are not well-recognised. The aim of this study was to evaluate the clinical and pathological aspects of corticotroph macroadenomas with particular emphasis on proliferation markers and their associations with the efficacy of surgical treatment. Design: A prospective cohort study was conducted in a tertiary referral centre in Poland. Methods: In total, 59 patients with CD (20 macroadenomas and 39 microadenomas) were included in this study. Hormonal and imaging parameters, histopathological and ultrastructural features of the corticotroph tumours and the early surgical outcomes were evaluated. Results: ACTH and ACTH/cortisol ratios were higher in macroadenomas (P<0.001 and P=0.002 respectively). Greater tumour volumes were associated with higher Ki-67 and p53 expression (P-trend=0.009 and P-trend=0.024 respectively) and the rates of sparsely granulated adenomas (P-trend=0.036). Immediate postoperative remission and early biochemical remission rates were lower in macroadenomas compared to microadenomas (P<0.001). A logistic regression model showed that the immediate postoperative remission or early biochemical remission depended on tumour volume (P=0.005 and P=0.006 respectively) and invasiveness based on Knosp grades 3 and 4 for macroadenomas and a lack of surgical pseudocapsule for microadenomas (P=0.004 and P=0.007 respectively). Conclusion: Corticotroph macroadenomas differ from the more common microadenomas not only in terms of hormonal and imaging characteristics but also in terms of immunohistochemical and ultrastructural features and proliferation markers. The early effectiveness of surgery depends primarily on tumour volume and invasiveness.