[Performance of Knosp grade for cavernous sinus invasion of Cushing's disease]

Diagnostic value of Knosp grade and modified Knosp grade for cavernous sinus invasion in pituitary adenomas: a systematic review and meta-analysis

OBJECTIVE

This study aimed to examine the reliability of existing Knosp grade (KG) and modified KG for cavernous sinus invasion (CSI).

METHODS

A thorough search of literature from 1993 to 2020 in six databases was performed. Studies that reported the intraoperative confirmation of CSI using KG and/or modified KG were included. The pooled estimates were calculated by meta-analysis with a bivariate mixed-effect model and the assessment of heterogeneity with I² statistic.

RESULTS

The final search yielded 12 eligible studies, which enrolled 3006 patients assessed with KG and 1315 patients assessed with modified KG. The results of the area under the receiver operating characteristic curve showed the good discriminative abilities of grades 2-4 (0.90), 3-4 (0.86) and 3B-4 (0.91) in predicting CSI. Grade 3A showed a remarkably lower CSI rate (44% versus 81%) and incomplete resection rate (26% versus 52%) than grade 3B. Grades 0 and 1 showed a low CSI rate. CSI and incomplete resection rates in grade 2 (30% and 21%, respectively) were close to those in grade 3A.

CONCLUSIONS

Modifying the KG improved its prognostic role in CSI and gross total resection. However, these grading systems cannot be used as the group standard for invasive and non-invasive pituitary adenomas (PAs) because of the weak reliability of the scale's middle grades (grades 2 and 3A). Authors of future PA studies should consider reporting KG as high (grades 3B and 4), medium (grades 2 and 3A) and low (grades 0 and 1) to optimise the application of the scale.

Neuroimaging of aggressive pituitary tumors

Aggresssive pituitary tumors are defined as radiologically invasive, exhibiting a rapid growth and a poor response to the medical and surgical treatment options. The role of magnetic resonance imaging (MRI) is fundamental to assess tumor aggressiveness before surgical exploration. Distinction between cavernous sinus invasion and cavernous sinus compression is often challenging and cannot be solved always by using the Knosp criteria. Ideally, T2W images demonstrating the ruptured internal dural wall of cavernous sinus is the ultimate proof of cavernous sinus invasion. Subtle tumor volume increase in a short time can be shown when sequential MR images are rigorously replicable. A microcystic pattern observed on T2W images frequently reflects a potentially aggressive tumor as observed in silent corticotroph pituitary adenomas.

UPDATES IN AGGRESSIVE PITUITARY TUMORS

Aggressive pituitary tumors lie between pituitary adenomas and carcinomas, displaying a particular behavior, with invasion, resistance to conventional therapy and early recurrence. The radiological grading, along with prognostic markers such as Ki-67 proliferation index, p53, MGMT and transcription factors are important factors in establishing the benign, aggressive, or malignant nature of pituitary tumors, with a more accurate treatment strategy. In this article, we report the novelties in defining, classifying, and managing aggressive pituitary tumors and their malignant potential, focusing on clinicopathological, histological, molecular and radiological data.