Clinicopathological features and survival outcomes of rare histologic variants of gallbladder cancer.

Background: Adenocarcinoma (AC) is the most common histological type in gallbladder carcinoma (GBC). Squamous cell carcinoma (SCC), adenosquamous carcinoma (ASC), and papillary carcinoma (PC) are rare histologic variants of GBC.

Methods: Patients with AC, SCC, ASC, and PC of the gallbladder between 2004 and 2013 were identified from the National Cancer Database. Univariate and multivariate analyses were performed, and Kaplan-Meier curves were used to compare overall survival (OS) based on histological subtype.

Results: A total of 5956 patients ≥18 years of age were included in the final analysis. Most patients (n = 5398; 90.6%) had AC compared with variant histologies. PC (n = 227; 3.8%) was the most common variant, followed by ASC (n = 216; 3.6%) and SCC (n = 115; 1.9%); 70.3% were female and 78.9% Caucasian. The median age was 70 (range, 25-90) years. Surgical resection was performed in 77.7% of AC, 53.0% of SCC, 88.9% of ASC, and 96.9% of PC (P < .001). Systemic therapy after surgery was administered in 25.1% of AC, 18.3% of SCC, 35.7% of ASC, and 19.4% of PC (P = .001). In multivariate analysis, multiagent chemotherapy was associated with improved OS in all histologies except for SCC and PC (p < .001), and adjuvant systemic therapy was associated with improved OS in ASC and AC (P < .001).

Conclusion: Survival differs between the gallbladder variants. Except for SCC, GBC variants underwent surgical resection more often than AC. Adjuvant systemic therapy was associated with improved OS in ASC and AC.