Meera Sekar MD, Presenter: Nothing to Disclose

Sughra Raza MD, Abstract Co-Author: Research grant, Hitachi, Ltd

Eugene Mun Wai Ong MBBS, FRCR, Abstract Co-Author: Nothing to Disclose

Robyn L. Birdwell MD, Abstract Co-Author: Nothing to Disclose

To evaluate outcome of MR detected breast lesions ≤ 5 mm by correlating imaging characteristics with pathology.

Review of 565 lesions biopsied with MR guidance from 3/04–2/09 identified 68 masses in 61 patients, ≤ 5 mm in greatest dimension. Diagnostic MR examinations leading to biopsy were prospectively read by 1 of 13 breast radiologists. For this study, 2 radiologists, blinded to final pathology, re-reviewed the MR exams recording the following by consensus: lesion size, location, shape, margins, kinetics (visually assessed), and T2 signal intensity, using ACR BI-RADS lexicon-based terms. While by BI-RADS definition an enhancing lesion <5 mm is a focus, for this study where margins were assessed and biopsy recommended, we refer to such lesions as masses. Chart review provided indication for MR including extent of disease, surveillance, problem solving, monitoring chemotherapy, or follow-up of previous findings; pertinent history including risk factors, and final pathology.

Of 68 masses, 36 were 5mm, and 32 were 3-4 mm. Biopsy revealed malignancy in 15 of 68 for an overall malignancy rate of 22.1 %. Of masses < 5mm, 9 of 32 (28.1%) were malignant. Of 15 malignancies 7 (46.7%) were in patients with a recently diagnosed breast cancer, 6 in the same breast. Of these 6, 4 (66.7%) were in the same quadrant. However, the higher likelihood of malignancy based on proximity to known cancer was not statistically significant. No difference in proportion of malignancies was found based on shape or margins. There was a higher proportion of malignancies in patients who had MR for follow up of a previous MR finding (n=4, p=0.04), and those with washout kinetics (p=0.04). T2 signal did not predict benign or malignant outcome.

PPV for malignancy of ≤ 5mm MR detected masses was 22.1%. For masses < 5mm, it was 28.1%. The decision to biopsy small lesions should therefore be based on carefully assessed MR features and patient risk factors, not solely on size.

Compared to the previously published data with low malignancy rate for small MRI-detected masses, our malignancy rate of 22% suggests that small size alone should not dissuade from biopsy.

Sekar, M, Raza, S, Ong, E, Birdwell, R, Small Masses on Breast MR: Is Biopsy Necessary?.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8004846.html