We studied outcomes of 147 patients with stage I/II grade 1 (32 pure tubular, 115 ductal) carcinoma treated with breast-conserving therapy to evaluate the prognostic usefulness of standard and recently proposed revised criteria for tubular (tubularity percentage [proportion of neoplastic cells adjacent to open lumens], nuclear grade, and mitoses) and ductal carcinoma. Carcinomas with less than 70% tubularity were ductal. Carcinomas with 70% or more tubularity were divided into those with occasional grade 2 nuclei and mitoses and those with pure grade 1 nuclei and rare or no mitoses. The 10-year disease-free survival for patients with pure ductal vs pure tubular carcinoma was 91% vs 96% (P = .036). Overall survival rates were similar (85% vs 89%; P = .161). With the recently proposed criteria, neoplasms with less than 70% tubularity; 70% or more tubularity and occasional grade 2 nuclei and mitoses; and 70% or more tubularity, pure grade 1 nuclei, and rare mitoses had 10-year disease-free survival rates of 88%, 93%, and 100% (P < .001) and 10-year overall survival rates of 85%, 88%, and 94%, respectively (P < .001). Tubular carcinoma as a distinct morphologic entity should be restricted to neoplasms with 70% or more tubularity, pure grade 1 nuclei, and rare mitoses. Other definitions of tubular carcinoma do not guarantee the excellent prognosis.