ACTH Silent Tumors of the Clivus: Surgical Management and Outcome

Introduction: Silent corticotroph adenomas (SCAs) are clinically nonfunctioning pituitary adenomas (NFPAs) with positive staining for corticotropin (ACTH) by immunohistochemistry. SCAs are a subtype of nonfunctioning pituitary tumor that are believed to behave more aggressively with a presumed higher risk of recurrence. These tumors typically present in the sellar/suprasellar space with associated optic nerve/chiasm compression. We report here a series of patients in whom the tumor presented as an unusual infrasellar clival mass.

Methods: We conducted a retrospective review of all SCA tumors followed at two institutions over a 9-year period. Out of these, we identified 11 cases of clival tumors that turned out to be SCA tumors. We reviewed all clinical, radiological, and pathological features. These patients were then followed up with serial imaging and clinical studies. We compared these results with the known literature on SCA tumors.

Results: Out of the 11 patients that met inclusion criteria, 55% were men with an average age of 52 years. The range of follow-up was 6-78 months with an average time of 46 months. Twenty-seven percent of patients presented with visual compromise and 36% with diplopia. The average tumor size was 4.4 cm in diameter with 36% of patients displaying cavernous sinus involvement and 90% with clival bony erosion. A gross total resection (GTR) was only attempted on 36% of patients; 90% of patients received post-diagnosis radiation therapy (IMRT). Of these, 50% continued to grow in the follow-up period on serial imaging.

Conclusion: SCA tumors are a distinct pathological subtype of nonfunctioning pituitary tumor that can present as a primary clival (infrasellar) lesion in a population of patients. The tumors in this location appear to present at a later age with a larger size and cavernous sinus invasion compared with other described cases of SCA. These tumors also present more with CN6 neuropathy than visual compromise, similar to other clival lesions. The degree of bony invasion and resistance to postoperative radiation therapy in a subset of these patients may support the thesis that SCAs behave more aggressively and can easily mimic other clival tumors on presentation. Due to their pathology and location, a GTR may not be indicated. Careful monitoring of the tumor is important in the postoperative period as a subset are resistant to standard radiation therapy.