2026 Proffered Presentations
S282: PROGNOSTIC IMPACT OF KI-67 INDEX AND TUMOR SIZE ON STRUCTURAL OUTCOMES IN NONFUNCTIONING PITUITARY NEUROENDOCRINE TUMORS
Edgar G. Ordonez-Rubiano1; Laura Baeza-Antón2; Carlos E. Jimenez-Canizales2; Juan Andrés Salas Henao1; Gabriela Ballesteros Oviedo1; Johan Estiven Vargas-Vargas1; Rafael Parra-Medina1; William Rojas García1; 1University Foundation of Health Sciences: Fundacion Universitaria de Ciencias de la Salud Bogota, Cundinamarca COLOMBIA; 2Hospital Comarcal de Melilla, Melilla, Spain
Introduction: Nonfunctioning pituitary neuroendocrine tumors (NF-PitNETs) represent the most common subtype of pituitary neoplasms. Although generally slow-growing, a subset demonstrates invasive or recurrent behavior. Potential predictors of aggressiveness include adrenocorticotropic hormone (ACTH) immunopositivity, plurihormonal or null-cell phenotype, Ki-67 index ≥3%, and tumor size ≥40 mm. Evidence regarding their prognostic value remains inconsistent. This study aimed to evaluate the association between these variables and structural persistence following surgery in a large Latin American cohort.
Methods: A retrospective review of medical records from 2010–2020 identified patients with surgically treated pituitary tumors. Inclusion criteria were MRI-confirmed NF-PitNET, complete clinical, radiological, and pathological records, and at least 12 months of follow-up. Eighty-one patients met criteria. Demographic data, presenting symptoms, imaging features, surgical approach, histopathological subtype, and postoperative outcomes were collected. Immunohistochemistry classified tumors by cell lineage and Ki-67 index, with ≥3% considered high. Structural persistence was defined as residual tumor on follow-up MRI. Statistical analyses included univariate description and Fisher’s exact test for associations with structural outcomes.
Results: Of 140 pituitary tumors reviewed, 81 (58%) were NF-PitNETs. The mean age was 51 years, with 53% female patients. Most tumors were macroadenomas (74%), with 13% classified as giant adenomas. Transsphenoidal surgery was performed in 80%, and 20% underwent a transcranial approach. The most frequent presenting symptoms were visual field disturbances (70%) and headache (66%).
Histopathology revealed gonadotroph lineage as the most prevalent (56%), followed by null-cell (24%) and corticotroph (19%). Ki-67 indices were available for 67 patients; 78% demonstrated Ki-67 ≥3%. Structural persistence was observed in 73% of the entire cohort, and 31% required reoperation.
Statistical analysis showed significant associations between Ki-67 ≥3% and structural persistence (p = 0.028) and between tumor size ≥40 mm and structural persistence (p = 0.030). Patients with Ki-67 ≥3% had a 100% incidence of persistence, compared to 72% in those with Ki-67 <3%. Similarly, all patients with tumors ≥40 mm exhibited persistence, compared to 68% with tumors <40 mm.
Conclusion: In this cohort, NF-PitNETs demonstrated high rates of persistence following surgical resection. Elevated Ki-67 index (≥3%) and large tumor size (≥40 mm) were strongly associated with poor structural outcomes. These findings support the role of Ki-67 and tumor size as accessible prognostic markers that may guide surgical planning, patient counseling, and postoperative surveillance strategies. Further studies incorporating molecular profiling and long-term outcomes are warranted to refine prognostic models in NF-PitNETs.
Keywords: Nonfunctioning pituitary neuroendocrine tumors, Ki-67 index, tumor size, surgical outcomes, recurrence.
