Breast ductal carcinoma in situ with microinvasion

Abstract

BACKGROUND The significance of microinvasion is still debated and clinical management is controversial. The authors defined ductal carcinoma in situ with microinvasion (DCIS‐MI) as DCIS with infiltration of the periductal stroma by a few tumor cells, singly (type 1) or in clusters (type 2). With this definition, the authors attempted to evaluate the clinical significance of microinvasion. METHODS The authors compared the clinical, pathologic features, and survival (median follow‐up, 7.3 years) of 1248 patients with, respectively, DCIS (722 patients), DCIS‐MI with microinvasion type 1 and type 2 (243 patients), and invasive ductal carcinoma in situ with a predominant DCIS component greater than or equal to 80% of the tumor (IDC‐DCIS, 283 patients). RESULTS Microinvasion was associated with DCIS histologic type, grade, and extent (respectively, P < 10⁻⁸, P < 10⁻³, P < 10⁻⁴). Axillary lymph node metastases were observed in a few patients with DCIS and DCIS‐MI type 1 (respectively, 1.4% and none), in 10.1% with DCIS‐MI type 2 and in 27.6% with IDC‐DCIS. Metastasis free and overall survival probabilities were significantly different between three groups in the following order from best to worst prognosis: 1) the group comprising DCIS and DCIS‐MI type 1, 2) the DCIS‐MI type 2 group, and 3) the IDC‐DCIS group. CONCLUSIONS The authors' results suggest there are two types of DCIS‐MI: 1) type 1 that behaves like DCIS and should be managed as such; 2) type 2 that is less pejorative than IDC‐DCIS but is more so than type 1. Cancer 2002;94:2134–42. © 2002 American Cancer Society. DOI 10.1002/cncr.10451