Challenging Knosp high-grade pituitary adenomas

Abstract

OBJECTIVEParasellar growth is one of the most important prognostic variables of pituitary adenoma surgery, with adenomas regarded as not completely resectable if they invade the cavernous sinus (CS) but potentially curable if they displace CS structures. This study was conducted to correlate surgical treatment options and outcomes to the different biological behaviors (invasion vs displacement) of adenomas with parasellar extension into the superior or inferior CS compartments or completely encasing the carotid artery (Knosp high grades 3A, 3B, and 4).METHODSThis was a retrospective cohort analysis of 106 consecutive patients with Knosp high-grade pituitary adenomas with parasellar extension who underwent surgery via a primary endoscopic transsphenoidal approach between 2003 and 2017. Biological tumor characteristics (surgical status of invasiveness and tumor texture, 2017 WHO classification, proliferation rate), extent of resection, and complication rate were correlated with parasellar extension grades 3A, 3B, and 4 on preoperative MRI studies.RESULTSInvasiveness was significantly less common in grade 3A (44%) than in grade 3B (72%, p = 0.037) and grade 4 (100%, p < 0.001) adenomas. Fibrous tumor texture was significantly more common in grade 4 (52%) compared to grade 3A (20%, p = 0.002), but not compared to grade 3B (28%) adenomas. Functioning macroadenomas had a significantly higher rate of invasiveness than nonfunctioning adenomas (91% vs 55%, p = 0.002). Mean proliferation rate assessed by MIB-1 was > 3% in all groups but without significant difference between the groups (grade 3A, 3.2%; 3B, 3.9%; 4, 3.7%). Rates of endocrine remission/gross-total resection were significantly higher in grade 3A (64%) than in grade 3B (33%, p = 0.021) and grade 4 (0%, p < 0.001) adenomas. In terms of complication rates, no significant difference was observed between grades.CONCLUSIONSAccording to the authors’ data, the biological behavior of pituitary adenomas varies significantly between parasellar extension patterns. Adenomas with extension into the superior CS compartment have a lower rate of invasive growth than adenomas extending into the inferior CS compartment or encasing the carotid artery. Consequently, a significantly higher rate of remission can be achieved in grade 3A than in grade 3B and grade 4 adenomas. Therefore, the distinction into grades 3A, 3B, and 4 is of importance for prediction of adenoma invasion and surgical treatment considerations.

Pituitary Adenomas and Invasiveness from Anatomo-Surgical, Radiological, and Histological Perspectives: A Systematic Literature Review

“…In 2015, the group led by Knosp suggested a subdivision of grade 3 into 3A and 3B ( Figure 5): in Grade 3A, the tumor extends laterally in the superior compartment of the cavernous sinus, whereas in Grade 3B the lesion extends laterally, but in the inferior compartment [60]. The same group has shown that grade 3A PAs have a lower rate of invasive growth than adenomas extending into the inferior cavernous sinus compartment or encasing the carotid artery (i.e., grade 3B and 4) [109]. This finding is clinically and biologically relevant, and is most probably the consequence of better surgical visualization provided by an endoscope: the improved possibility of visually checking the medial wall of the cavernous sinus intraoperatively, behind the cavernous ICA loop, has shown that the medial wall can be frequently displaced and not invaded in grade 3A PAs; in other cases, it can be spontaneuosly dehiscent and provide a natural corridor for extension of PAs in the cavernous sinus [62].…”

Surgical treatment of aggressive pituitary adenomas and pituitary carcinomas

“…Jane et al [30] demonstrated this very convincingly in patients with acromegaly who underwent endoscopic transsphenoidal operations by using the Knosp score [18,19]. Micko et al [20] likewise confirm, that endocrine remission can hardly ever be expected in tumors with major parasellar invasion. Once this is determined in the MRI, usually tumor within the cavernous sinus will remain, whatever technical modifications are used.…”

“…Tumor lateral of the course of the carotid artery ( Fig. 5) generally speaking is deemed not to be completety resectable [5,20]. This has prognostic significance for the chance to totally resect a pituitary tumor and consequently also to achieve endocrine remission in hormonally active pituitary adenomas.…”

Microsurgical and Endoscopic Anatomy of the Cavernous Sinus

“…This possibility of expanding the field of view into the anterior portion of the CS has come to allow resection of tumor lesions arising in or encroaching upon this area, as reported recently by some authors. [2][3][4][5][6][7][8] The purpose of the present study is to describe the microsurgical and endoscopic anatomy of the CS, as well as to compare the visualization of the surgical triangles through both views.…”