Arpita Swami MBBS, Presenter: Nothing to Disclose

Eva Csilla Gombos MD, Abstract Co-Author: Research support, General Electric Company Medical Advisory Board, Bayer AG

Sona Ajit Chikarmane MD, Abstract Co-Author: Nothing to Disclose

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

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

We reviewed pectoralis muscle enhancement (PME) on breast magnetic resonance (MR) imaging in patients with history of breast conservation therapy (BCT).

This retrospective HIPAA-compliant study was approved by our IRB. Between 8/1/05 and 7/31/07, 481 women underwent post-BCT MR examinations on 1.5T scanners. Data collected included patient demographics, characteristics of PME, time interval between BCT and MR exam, location of lumpectomy in relation to the pectoralis muscle, follow-up and biopsy results. All data were entered into two computerized spreadsheets (Excel, Microsoft and SPSS, v12.0).

In 43 of 481 cases (9%), the pectoralis muscle was not adequately seen. In 333 of the 438 patients, there was no enhancement within the muscle. In 105/438 (24%) cases with treatment changes close to the muscle, variable PME was observed at 0.3 -19 years following BCT (mean of 2.1 years). In 78/105 (75%) cases the PME was diffuse and in 27/105 (25%), cases it was focal. There was no suspicious mass-like enhancement within the muscle; non-mass-like focal area or diffuse enhancement with persistent delayed kinetics was observed. Mastectomy was performed in 8 patients who were diagnosed with recurrence; in 1 case histology reported muscle involvement by recurrent tumor. Slightly nodular focal persistent enhancement was noted in this single case of proven recurrence in the pectoralis muscle. The remaining 97/105 cases were followed clinically (n=80) and by imaging (n=80) for 7 - 53 months (mean = 25 months). MR of 56 cases showed stability or resolution of enhancement at follow-up at 6 - 42 months (mean 21 months). No new recurrence was reported to date.

While in primary cancer muscle enhancement is a strong indicator of muscle invasion, in post treatment breast it is a commonly seen and benign finding; and it was present in this study in 105 out of 438 cases (24%) at a mean of 2.1 years following BCT. Pathology reported involvement of the muscle by malignancy in one case concurrently with in-breast recurrence. We conclude that cases can be followed if they demonstrate no suspicious mass-like or nodular enhancement.

Pectoralis muscle enhancement is commonly seen after breast conservation therapy. Certain types of focal as well as diffuse pectoralis muscle enhancement can be followed to ensure stability.

Swami, A, Gombos, E, Chikarmane, S, Raza, S, Birdwell, R, Imaging of the Pectoralis Muscles by Contrast-enhanced Breast Magnetic Resonance Imaging Following Conservative Therapy for Breast Cancer.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8008028.html