Anatomic Pathology / REFINED MORPHOLOGIC CRITERIA FOR TUBULAR CARCINOMA

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. Invasive tubular carcinoma is a morphologically distinct subtype of carcinoma with a favorable outcome compared with grade 1 ductal carcinoma.1-13 The excellent prognosis of tubular carcinoma stems from studies in which most patients were treated with mastectomy and were compared with patients with ductal carcinomas that were several centimeters larger. We recently completed a complete pathologic review of 607 invasive breast carcinomas from 583 patients treated with breast-conserving therapy at our institution and found invasive carcinoma morphologic features were not associated independently with outcome.14 This prompted us to question whether patients with tubular carcinoma continued to have significantly better outcomes than patients with grade 1 ductal carcinoma among contemporary breast carcinoma patients treated with breast-conserving therapy. The definition of tubular carcinoma is not precise. Authors have allowed 0% to 25% admixture of usual-type ductal carcinoma.3,4,6,8,10,11,15-17 Furthermore, it often is difficult to determine whether an individual duct is sufficiently “tubular” in appearance to qualify as tubular carcinoma. Invasive ductal carcinomas with some but not all morphologic features of tubular carcinoma are common.18 These morphologic issues recently were addressed in a study in which the authors found tubularity percentage, defined as the proportion of neoplastic cells that were adjacent to open lumens, nuclear grade, and mitoses, could be used to separate tubular and ductal carcinomas.18 Invasive carcinomas with more than 70% tubularity, grade 1 nuclei, and very rare mitoses had no lymph node metastases or breast carcinoma–associated deaths. To our knowledge, the prognostic strength of these morphologic criteria has not been examined by another group of authors and compared with standard criteria for tubular carcinoma. Anatomic Pathology / ORIGINAL ARTICLE Am J Clin Pathol 2004;122:728-739 729 729 DOI: 10.1309/9FEP8U8AUGQNGY3V 729 © American Society for Clinical Pathology The goals of this study were to evaluate whether tubular carcinoma continued to have a more favorable prognosis than grade 1 ductal carcinoma in contemporary breast carcinoma patients and to compare the prognostic strength of the recently proposed tubular carcinoma criteria with standard criteria. Materials and Methods