Unexpected Residual after Endoscopic Transsphenoidal Surgery for Large and Giant Pituitary Adenomas

Introduction: Pituitary adenomas constitute approximately 5 to 15% of all intracranial tumors. Most commonly, giant and large pituitary adenomas are defined by their largest diameter >4 cm and >3 cm, respectively. Gross total resection after transsphenoidal pituitary surgery for giant pituitary adenomas is reported to be from 40 to 50%. To our best knowledge, there is no data on unexpected residual tumor after TSPS for large and giant adenomas, meaning residual tumor which felt to have been completely resected.

Methods: Medical records and imaging were queried for all patients who underwent transsphenoidal pituitary surgery between January 2015 and December 2018 at our institution. Only patients operated on by two experienced high volume pituitary were included (134 patients).

Results: Forty patients (13 females and 27 males) were included, comprising 30 large and 10 giant pituitary adenomas, respectively. The mean age was 57.85 ± 14.75 years (range = 25–80 years). The mean MRI follow-up time was 5.9 ± 6.54 months (range = 0–24) postresection. Intraoperative CSF leak occurred in 14 patients (35%): in seven (23.3%) with large and seven (70%) with giant PA (p = 0.007). Postoperative CSF leak occurred in three patients (7.5%).

In patients with large PAs, gross total resection (GTR) was achieved in 25 patients (83.3%), subtotal resection (STR) in four (13.3%), and inconclusive in one (3.3%). In patients with giant PAs, GTR was achieved in four patients (40%), STR in five (50%), and inconclusive in one (10%). Residual tumors were identified in nine (22.5%) patients, of which seven (77.7%) were unexpected. Increased longest working distance (LMax) was significantly associated with all residual tumors (p = 0.049). LMax was measured from the most anterior point of the sellar floor to the furthest tumor margin. Suprasellar width, height, and AP of the tumor were not associated with residual tumor (p = 0.599, p = 0.651, and p = 0.171, respectively. A statically significant association between unexpected residual tumor and larger retrosellar extension as well as increased LMAx were observed (p = 0.003 and p = 0.018, respectively). No association was observed with suprasellar height, width, AP dimension, and unexcepted tumor residual (p > 0.05). Analysis of intraoperative factors associated with presence of unexpected residual tumors revealed one case in which suspicious tissue was not removed due to uncertainty of its nature (tumor vs. gland). In one case, angled endoscope visualized suspicious tissue which was subsequently removed; however, follow-up MRI revealed residual tumor in the same location. Premature herniation of diaphragm was identified as contributing factor in one case. No factors were identified in remaining four cases.

Conclusion: Complete tumor resection in giant pituitary adenomas is achieved in minority of cases. Intraoperative visualization and assessment seem to be unreliable. Supplemental means of identifying residual tumor in transsphenoidal pituitary surgery for giant and large pituitary adenoma might increase the resection rate in patients with unexpected residual adenoma, in whom GTR is anatomically possible.

No conflict of interest has been declared by the author(s).