Adenosquamous carcinoma of the breast, an uncommon diagnosis with poor prognosis-Lessons learned from a 12-year analysis of the National Cancer Database.

We compared the clinicopathologic characteristics and prognosis of adenosquamous carcinoma (ASQ) of the breast with invasive ductal carcinoma (IDC), utilizing the National Cancer Database (NCDB) from 2004 to 2015. 1 932 688 female patients had invasive breast carcinoma; 1 421 250 had IDC (73.5%); and 453 had ASQ (0.0002%). When compared to IDC, ASQ patients were significantly (P < .05) older and had grade 1 tumors; negative lymph nodes; ER/PR/HER2-negative tumors; and worse 5-year overall survival (64.9% vs 74%, respectively). Our study, largest to date on ASQ, revealed an aggressive carcinoma with a significantly worse prognosis than IDC. "Personalized medicine" treatment approach for patients with this uncommon carcinoma is needed.