Radiologic Features of Triple Negative Breast Cancer

Triple negative (TN) breast cancer is defined as cancer with negative expressions of hormone receptors and human epidermal growth factor receptor 2 (HER2). This subtype is characterized as a cancer with a high malignancy potential and a poor prognosis. Endocrine therapy and anti-HER2 therapy are ineffective in the treatment of TN breast cancer as they have less specific targets compared with other subtypes of breast cancer. At present, chemotherapy is the only option to treat this type of cancer. This subtype is found in approximately 15.5% of all breast cancer cases in Japan (Iwase et al., 2010). The percentage of other subtypes are as follows; Luminal A (hormone receptors positive and HER2 negative), 69.0%; Luminal B (hormone receptors positive and HER2 positive), 7.3% and HER2-enriched (hormone receptor negative and HER2 positive), 8.2%. Some reports described a subtype of DCIS that correlates to the progression to invasive carcinoma; comedo type DCIS progresses to invasive carcinoma, both more often and more rapidly than low-grade DCIS (Pinder SE & Ellis IO, 2003; Ketcham AS & Moffat FL, 1990). This may be a reason for the rarity of TN DCIS. The incidence of TN DCIS accounts for less than 5% of DCIS. If this is true, early detection of this particularly aggressive type of breast cancer is vital. (Moriya et al, 2010) There have been reports claiming that TN IDC occurs from ER negative, HER2 positive DCIS lesion and loses its HER2 expression when it progresses to an invasive cancer, which may indicate a precursor process is at work (Bradley BB et al., 2006; Livasy CA et al., 2007; Flora Z et al., 2007). To clarify these hypotheses, comparison between TN IDC and TN DCIS is also essential. There are no other reports that we were able to find that focus specifically on TN DCIS. We cannot predict the outcome of TN DCIS, if it is not diagnosed and treated, because this has not been researched nor documented (Page DL et al., 1995; Page DL et al., 1982; Betsill WLJ et al., 1978). We reviewed another report on a series of cases in which DCIS was not completely excised. The findings from those reports indicate that a more frequent and rapid progression from DCIS to invasive cancer is related to the comedo subtype of DCIS, which is comparable to low-grade DCIS (Pinder SE & Ellis IO, 2003; Simpson JF, 2009). We need to investigate the specific features of this subtype, and we need to determine the radiological and pathological features of TN breast cancer via retrospective evaluation in a large population, in order to make a more precise diagnosis.