Context.-Mammographic screening has increased the incidence of ductal carcinoma in situ (DCIS), but this has not been accompanied by a decline in the incidence of invasive carcinoma (IC). Consequently, the surgical treatment of DCIS has recently been questioned, with some advocating only surveillance (with or without neoadjuvant endocrine therapy) after a core biopsy diagnosis of DCIS.Objectives.-To examine the predictive value of a core biopsy diagnosis of DCIS, particularly the upgrade rate to IC, and to identify associated factors.Design.-Using the pathology database, we identified 2943 cases of DCIS diagnosed on core biopsy from 2000 to 2015, of which 229 cases (8%) later had the stage upgraded to IC.Results.-Ages ranged from 25 to 90 years (mean, 59 years). The DCIS presented with calcifications in 151 of 229 cases (65.9%), was widespread in 26 of 151 cases (17%), had a mass or density present in 70 of 229 cases (31%), with heterogeneous echogenic features in 44 of those 70 cases (63%), and an enhancement upon magnetic resonance imaging in 8 of 229 cases (3.5%). Of the 229 cases, the DCIS grades were as follows: low in 29 cases (13%), intermediate in 79 cases (36%), and high in 121 cases (53%). Of the 229 cases, necrosis was present in 152 (66.4%) and was comedo necrosis in 99 cases (43%). Of the 229 cases of IC, the tumor stage was as follows: microIC in 36 (16%), T1a in 119 (52%), T1b in 35 (15%), T1c in 28 (12%), T2 in 8 (3%), and T3 in 3 cases (1%). Axillary lymph nodes were staged in 167 patients as follows: N0, 141 cases (84%); N0(iþ), 14 cases (8%); and N1, 12 cases (7%). The 12 N1 cases were subclassified by T stage as follows: T1a, 1 case (8%); T1b, 4 cases (33%); T1c, 2 cases (17%); T2, 4 cases (33%); and T3, 1 case (8%). The IC cases of stage upgrading were predominantly smaller than 2 cm (218 of 229; 95%), and more than twothirds were smaller than 0.5 cm (155 of 229; 95%), most of which were accompanied by extensive DCIS.Conclusions.-Approximately one-half of the upgrades were associated with high-grade DCIS, especially with comedo necrosis; nevertheless, the other one-half of the upgrades were due to low-and intermediate-grade DCIS and should not be underestimated. There were few positive results from axillary lymph node biopsies, but they occurred in 3% (7 of 218) of the carcinomas smaller than 2 cm. Our findings indicate that caution is needed when DCIS cases diagnosed by core biopsy are treated nonsurgically with surveillance (with or without neoadjuvant endocrine therapy), given the number of cases (229 of 2943; 8%) that are upgraded to IC and those with axillary lymph node metastases (12 of 167; 7%).
