The shape of breast cancer

Purpose Little is known about the three-dimensional shape of breast cancer. Implicit to approaches that localize the center of the tumor for breast-conserving surgery (BCS) of non-palpable cancers is the assumption that breast cancers are spherical about a central point, which may not be accurate. Methods Pre-operative supine breast MRI images were obtained of 83 breast cancer patients undergoing partial mastectomy using supine MRI-guided resection techniques. Three-dimensional (3D) tumor models were derived after radiologists outlined tumor edges on successive MRI slices. Ideal resection volumes were determined by adding 1 cm in every dimension to the actual tumor volume. Geometrically defined parameters were used to define tumor shapes and associations between clinical variables and shapes were examined. Results Seventy-five patients had invasive cancer. Breast cancers were categorized into four tumor shapes: 34% of tumors were discoidal, 29% segmental, 19% spherical, and 18% irregular. If hypothetical spherical excisions were performed, non-spherical cases would excise 143% more tissue than the ideal resection volume. When the 3D shape of each tumor was provided to the surgeon during MR-guided BCS, the percentage of tissue overexcised in non-spherical cases was significantly less (143% vs. 66%, p