Simplified 2-tier histologic grading system accurately predicts outcomes in goblet cell carcinoid of the appendix

Goblet cell carcinoid (GCC) is a rare appendiceal malignancy with both neuroendocrine and glandular features. Clinical outcomes of patients with GCC vary widely and a histology-based 3-tiered prognostic scheme has been previously suggested; however, this scheme is subjective and challenging to apply in day-to-day practice. We sought to construct a simplified and prognostic grading system based on objective histologic features with specific criteria. A continuous population-based cohort of GCC with clinical outcome data and archival tissue available for review was extracted from regional databases. For the 78 patients with confirmed appendiceal GCC, specific histologic features, including cytologic atypia, peritumoral stromal desmoplasia, and solid growth pattern, were recorded, and a scoring system was devised, which separates patients with GCC into low-grade (n = 55; 71%) or high-grade (n = 23; 29%) histology. Correspondingly, clinical follow-up data show good prognosis in those with low-grade histology with median and 10-year overall survival of 51.0 months and 80.5%, respectively, whereas those with high-grade histology have a poor prognosis with median and 10-year overall survival of 16.5 months (P = .006) and 0% (P < .001), respectively. Multivariate Cox proportional hazard modeling demonstrates that this 2-tier histologic system remains predictive of overall survival when controlled for TNM clinicopathological stage. These data show that a simple and objective histologic scoring system separates GCC into low- and high-grade histology with divergent clinical outcomes.