eP129 - Appendiceal Goblet Cell Carcinoma: Comparison of Current Classification and Staging Systems with Evaluation of Prognostic Role of Immunohistochemistry Stains

Purpose/Background: There is no standardization or consensus among institutions or scientific literature regarding the classification of appendiceal GCC. Similarly to the staging of adenocarcinoma, TNM staging has been used as a predictor for outcomes of GCC. Tang, Yozu, and Lee grading systems have been proposed to be more accurate in determining GCC outcomes when considering histological features. Inconsistence utilization of classification and staging systems make integrating and literature comparisons challenging. This study aims to evaluate a single institution patient population with GCC of the appendix. By comparing the four current classification systems, we hope to determine and further stratify which classification system should be utilized as the gold standard and whether there is a role for immunohistochemistry stains in determining the prognosis and outcomes of this tumor burden.Methods/Interventions: An electronic medical records review of patients who were diagnosed with GCC of the appendix in our hospital system from 2010 to 2020. Data was collected regarding the age at diagnosis, gender, initial diagnosis at presentation, operation(s) performed, final pathology results (staging and stains performed), current survival status, and year of recurrent disease or year of death (if applicable). Staging and grading of the patients used TNM, Tang, Yozu, and Lee classification systems.Results/Outcomes: Ten patients were evaluated. Nine patients presented as acute appendicitis, while one patient presented as a small bowel obstruction. Seventy percent of patients were above the age of fifty years at diagnosis; age range from 37-84 years old. One patient underwent reoperation secondary to positive margins. Post-discharge survival ranged from 1 month to 109 months post-diagnosis. Two patients expired from GCC at 13 months and 54 months following diagnosis; with one patient's death attributed to COVID-19. TMN staging, treatment, and survival outcomes demonstrated T1 (10%), T2 (20%), T3 (50%), and T4 (20%) disease. Using the Tang grading system, patients were classified as A (30%), B (60%), and C (10%). The Yozu system classified patients as low (60%), intermediate (30%), and high (10%). The Lee grading system classified patients as low (60%) and high (30%). When comparing the classification systems, Lee categorized more patients as high risk than Tang and Yozu. Immunohistochemical staining was analyzed using four staining methods: Ki67, E cadherin, Beta-catenin, and p53, this can be seen in Table 3. Ki67 ranged from 7% to 80% and was not significantly elevated in the patients who died from their disease. Our patient population was focally weak for p53. It is difficult to conclude which classification system is the most consistent. TNM staging has supportive evidence for worsening prognosis and overall survival secondary to the depth of invasion of the tumor.Conclusion/

Discussion: TNM staging may be superior to other classification systems in predicting overall mortality. Tang, Yozu, and Lee grading systems failed to determine survival outcomes accurately. It remains unclear which classification system should be used routinely. Our study demonstrated that immunohistochemistry staining does not appear to have a significant impact in determining the prognosis for GCC of the appendix. The most significant limitation of our study was a small sample size (n = 10). A multi-institutional study to further evaluate which classification system is most consistent when considering prognosis and survival for appendiceal GCC would be beneficial."Table 1

Summary of patient epidemiology, classification systems, treatments and overall survival outcomes. * Represents the patients who expired.
Table 2

Immunohistochemistry staining used to evaluate role in prognosis "