Large Subpectoral Lipoma on Screening Mammography

Abstract

A 61 year-old woman presenting for bilateral screening mammogram was found to have an oval fat-density mass in the posterior right breast, partially visualized, with anterior displacement and thinning of the pectoralis major muscle. This mass was found on CT and MRI correlation to represent a large fat-containing mass, likely a lipoma, deep to the pectoralis major. On subsequent screening mammograms, the visualized portion of the mass remained stable. Subpectoral lipomas and intramuscular lipomas within the pectoralis major are rare, and their appearance on mammography may not be familiar to most radiologists. A review of the literature and a discussion of their appearance on multiple imaging modalities is provided.

Keywords: MRI; chest; mammography; pectoralis major; subpectoral lipoma.

Figure 1

61 year-old woman presenting for screening mammogram. Findings: On MLO view of the right breast (a), an oval, circumscribed, fat-density mass (arrows) is partially visualized in the posterior breast, deep to the pectoralis major muscle, with anterior displacement and thinning of the muscle margin. No correlate is seen on CC view of the right breast (b). Diagnosis: Subpectoral lipoma. Technique: 106 mAs, kVp 30

Figure 2

61 year-old woman presenting for CT for abdominal pain. Findings: On the axial images, superiormost slices, an incompletely visualized, homogeneously fat-density mass (arrows) displaces the pectoralis major muscle anteriorly, and measures up to 4.5 × 0.8 cm on the available images. Diagnosis: Subpectoral lipoma. Technique: 306 mA, kVp 120

Figure 3

62 year-old woman presenting for MRI of the abdomen for further delineation of pancreatic hypodense lesion identified on CT. On the superiormost axial post-contrast T1-weighted images with fat suppression (a), a large intermuscular mass is partially visualized displacing the right pectoralis major anteriorly. The mass demonstrates uniform low signal on fat-suppressed images without any thick septation, nodular component, or internal enhancement. The mass is homogeneous and follows fat intensity on the non-fat-saturated coronal T2-weighted images as well (b). Diagnosis: Subpectoral lipoma. Technique: MR was performed on a GE® 3 T magnet. The parameters are as follows: a) axial T1-weighted sequence with fat suppression after administering 13 mL Multihance® gadolinium intravenous contrast (TR 4.063; TE 1.674), slice thickness 4.6 mm; b) coronal single-shot fast spin echo T2 (TR 1260.8; TE 98.736), slice thickness 5 mm.

Figure 4

62 year-old woman presenting for screening mammogram, with MLO and CC views respectively at one year (a, b) and four years (c, d) after initial screening mammogram. On the most recent mammogram, the mass was included for the first time on CC view (d) in the far posterior depth, resembling the contour of the normal pectoralis major muscle, but distinguished from muscle by the presence of fat density (arrows). Diagnosis: Subpectoral lipoma. Technique on 4/22/2013 mammogram (a, b): 139 mAs, kVp 30 Technique on 10/06/2016 mammogram (c, d): 103 mAs, kVp 30