Breast Cancers Found with Digital Breast Tomosynthesis: A Comparison of Pathology and Histologic Grade.

To compare the pathology and histologic grading of breast cancers detected with digital breast tomosynthesis to those found with conventional digital mammography. The institutional review board approved this study. A database search for all breast cancers diagnosed from June 2012 through December 2013 was performed. Imaging records for these cancers were reviewed and patients who had screening mammography with tomosynthesis as their initial examination were selected. Five dedicated breast imaging radiologists reviewed each of these screening mammograms to determine whether the cancer was visible on conventional digital mammography or whether tomosynthesis was needed to identify the cancer. A cancer was considered mammographically occult if all five radiologists agreed that the cancer could not be seen on conventional digital mammography. The size, pathology and histologic grading for all diagnosed breast cancers were then reviewed. The Mann-Whitney U and Fisher exact tests were utilized to determine any association between imaging findings and cancer size, pathologic type and histologic grade. Sixty-five cancers in 63 patients were identified. Ten of these cancers were considered occult on conventional digital mammography and detected with the addition of tomosynthesis. These mammographically occult cancers were significantly associated with Nottingham grade 1 histologic pathology (p = 0.02), were smaller (median size: 6 mm versus 10 mm, p = 0.07) and none demonstrated axillary nodal metastases. Breast cancers identified through the addition of tomosynthesis are associated with Nottingham grade 1 histologic pathology and prognostically more favorable than cancers identified with conventional digital mammography alone.