A new study has identified factors likely to be associated with upstaging to invasive breast cancer (based on pathological findings after surgery to remove the tumor) after an initial core needle biopsy diagnosis of ductal carcinoma in situ (DCIS). DCIS refers to cancer cells that have formed in milk ducts but are confined there. DCIS is classified as non-invasive because the abnormal cells have not spread beyond the walls of the duct to invade the surrounding breast tissue. If left untreated, some DCIS lesions will progress to invasive breast cancer.

The study sought to find preoperative factors that predict which DCIS patients are likely to be upstaged to invasive breast cancer and thus could benefit from sentinel lymph node biopsy at the time of initial surgery to remove the tumor. This would prevent such patients from having to go back for reoperation to have their sentinel nodes assessed. The study included patients at an Australian teaching hospital diagnosed between 1994 and 2006 whose core needle biopsy findings showed DCIS or DCIS with microinvasion (carcinoma less than 1 mm).

A total of 65 of 375 cases of DCIS and 11 of 15 cases of DCIS with microinvasion were upstaged to invasive cancer after surgery. Ten of 21 cases in which the tumor could be detected manually (i.e., it was palpable) were found to have microinvasion. For DCIS that was not detectable by hand, the presence of a mass, nonspecific density, or architectural distortion on mammogram, mammographic size of 20 mm or greater, and a screening interval of at least three years each were associated with upstaging. In addition, the DCIS grade on core needle biopsy was found to be a significant predictor of progression to invasive breast cancer. The likelihood of upstaging increased with the number of these factors present in a patient: 8.3% of patients with no risk factors were upstaged; 20.8% of those with one risk factor; 39.6% of those with two risk factors; and 57.1% of those with three risk factors. The authors conclude that the risk of upstaging to invasive breast cancer can be estimated by using preoperative features in patients found to have DCIS with core needle biopsy. The authors propose a patient management strategy that includes sentinel node biopsy for patients with DCIS who have microinvasion on core needle biopsy, palpable DCIS, two or more predictive factors, and/or planned total mastectomy.