Histopathology findings of non-mass cancers on breast ultrasound

Background There is little research done on non-mass cancers (NMCs) on breast ultrasound (US). Purpose To evaluate large-sectional histopathology findings of NMCs on breast US. Material and Methods The mammographic and histopathology features of biopsy proven 36 breast cancers which showed pure non-mass lesions on US were retrospectively reviewed. Results The most common mammographic finding was microcalcification (23/35, 65.7%); fine pleomorphic microcalcification was predominant (18/23, 78.3%). The main tumor type was pure ductal carcinoma in situ (DCIS) (14/36, 38.9%) and DCIS with micro- or minimal invasion (11/36, 30.6%). Among the 25 DCIS, histologic grade was high in 15 (60.0%) and intermediate in nine (36%); comedo necrosis was seen in 17 (68%). Immunohistochemical analysis was available in 27 lesions and showed HER2-overexpression in 12 (44.4%) and triple-negative in two (7.4%). Conclusion According to our limited patient sample, NMCs on breast US were mainly associated with high-grade DCIS.