|Paper title||The Shape-Classification: A new grading system for growth patterns of pituitary adenomas|
|Form of presentation||Poster|
OBJECT. Tumor size, invasion into the surrounding structures, and extent of growth have been described as factors influencing the outcome of transphenoidal tumor surgery. The classifications described by Knosp and Hardyhave proven helpful in comparing surgical results and predicting the patient’s outcome. While different growth patterns have been advocated as an additional factor, a standardized classification does not exist. The goal of this study is to assess the impact of a new grading system based on tumor shapes.
METHODS. Patients suffering from non-functioning pituitary adenomas, who underwent transsphenoidal surgery at our institution were elegible for inclusion. Shape grades resulted from measuring the tumors' max. diameters as follows:
Shape-I: spherical. In all sections the max. diameters do not differ >25%
Shape-IIA: oval shape, no cavernous sinus invasion (aka Knosp grade 0-2). One of the max. diameters differs >25% from the others
Shape-IIB: oval shape as defined for Shape-IIA, but with invasion into the cavernous sinus (aka Knosp grade 3 and 4)
Shape-III: Dumbbell-like appearance, caused by intra- and suprasellar growth with a constriction on the level of the sphenoidal plane. On the level of the constriction the max. diameter is at least 25% smaller than the maximum intra- and suprasellar diameters
Shape-IV: Mushroom-like appearance, caused by a maximum suprasellar diameter >50% larger than the intrasellar diameter
Shape-V: Polylobulated appearance caused by at least 3 parts of the tumor with max diameters >50% of the intrasellar part spreading in the supra-/parasellar confines, the sphenoid sinus, and/or the clivus
RESULTS. A total of 191 patients (Shape-I, n=28 (15%); Shape-IIA, n=66 (35%); Shape-IIB, n=25 (13%); Shape-III, n=37 (19%); Shape-IV, n=12 (6%); Shape-V, n=23 (12%)) were included in the study. The gross total resection (GTR) rate varied significantly between the different Shape-grades with higher grades being less likely to be totally resected. Invasion into the cavernous sinus only influenced the GTR rate in Shape-II tumors, which justifies subdividing Shape-II tumors into IIA and IIB. The finding of pre- and postoperative optic chiasm and pituitary stalk compression was significantly more frequent in higher Shape-grades.
CONCLUSION. The surgical outcome of nonfunctioning pituitary adenoma is influenced by the tumors' shape. The Shape-classification offers a standardized grading system to describe the different tumor shapes.