PDZ Binding Kinase (PBK) Immunoexpression in Invasive Pituitary Adenomas: An Exploratory Study

Abstract Although pituitary adenomas (PAs) are believed to be benign neoplasms, invasion and recurrence are known in these tumors. Invasive PAs may not be amenable to complete excision and hence pose a challenge in the surgical management. Few previous studies have identified matrix metalloproteinase and vascular endothelial growth factor as possible contributors to invasion in PA, with no conclusive evidence. We studied the expression of a novel biomarker, PDZ-binding kinase (PBK) in invasive PA. PBK has earlier been shown to contribute to aggressiveness in glioblastoma, by our group. A total of 23 invasive pituitary PAs were included. As controls, normal adenohypophysis and 10 noninvasive PAs were also studied. In all the cases, clinical, radiological, histopathological, and immunohistochemical profiles were analyzed. Invasion was defined based on radiological findings. Further, immunohistochemistry with PBK antibody was carried out and analyzed. Mean age in invasive PA was 47.6 years, in noninvasive PA was 48.6 years. The most common site of invasion was the cavernous sinus-unilateral (21.7%), and bilateral in 65.2%. The common presentation was vision involvement in both. The mean volume in the invasive group was 31.95 cc, and in the noninvasive group, it was 9.79 cc. The common surgical approach was the endoscopic transnasal approach in both groups. The majority of invasive (47.8%) and noninvasive (70%) PAs were gonadotroph adenomas. PBK immunopositivity was noted in 20/23 (87%) invasive PAs, while it was not observed in normal adenohypophysis or in any of the 10 noninvasive PAs. PBK is a highly sensitive immunohistochemical marker for invasive PA, which can be used for identifying and predicting invasion. The upfront adjuvant therapy can be planned based on the invasiveness of the PA.