Pancreatic neuroendocrine tumors: Are tumors smaller than 2 cm truly indolent?

Pancreatic neuroendocrine tumors (PNETs) are relatively rare but rank as the second most common pancreatic neoplasm. They can be functional, causing early metabolic disturbances due to hormone secretion, or non-functional and diagnosed later based on tumor size-related symptoms. Recent diagnoses of PNETs under 2 cm in size have sparked debates about their management; some practitioners advocate for surgical removal and others suggest observation due to the tumors' lower potential for malignancy. However, it is unclear whether managing these small tumors expectantly is truly safe.

To evaluate poor prognostic factors in PNETs based on tumor size (> 2 cm or < 2 cm) in surgically treated patients.

This cohort study included 64 patients with PNETs who underwent surgical resection between 2006 and 2019 at a high-complexity reference hospital in Medellín, Colombia. To assess patient survival, quarterly follow-ups were conducted during the first year after surgery, followed by semi-annual consultations at the hospital's hepatobiliary surgery department. Qualitative variables were described using absolute and relative frequencies, and quantitative variables were expressed using measures of central tendency and their corresponding measures of dispersion.

The presence of lymph node involvement, neural involvement, and lymphovascular invasion were all associated with an increased risk of mortality, with hazard ratios of 5.68 (95%CI: 1.26-25.61, P = 0.024), 6.44 (95%CI: 1.43-28.93, P = 0.015), and 24.87 (95%CI: 2.98-207.19, P = 0.003), respectively. Neural involvement and lymphovascular invasion were present in tumors smaller than 2 cm in diameter and those larger than 2 cm in diameter. The recurrence rates between the two tumor groups were furthermore similar: 18.2% for tumors smaller than 2 cm and 21.4% for tumors larger than 2 cm. Patient survival was additionally comparable between the two tumor groups.

Tumor size does not dictate prognosis; lymph node and lymphovascular involvement affect mortality, which highlights that histopathological factors-rather than tumor size-may play a role in management.