The Musculus Sternalis: Ultrasonographic Verification of a Rare but Benign Mammographic Finding

Abstract

Screening mammography requires high-quality images and experienced radiologists. An improved technique with a systematic approach to patient positioning enables visualization of the deep parts of the breast. The sternalis muscle is occasionally observed in mammograms as a variant of the deep normal structures and may mimic a mass. The sternalis muscle is an uncommon anatomic variant of the chest wall musculature. It is located subcutaneously over the pectoralis muscle and has a parallel course to the sternum. It runs from the infraclavicular area to the caudal aspect of the breast. This inconsistent muscle has varying shapes, contours and sizes and may mimic a mass lesion on the craniocaudal (CC) mammogram. Familiarity with its mammographic appearance and ultrasonographic correlation is essential to avoid confusion with a malignant lesion. In this case report, we describe mammographic and ultrasonographic imaging findings of the sternalis muscle and review the literature. The sternalis muscle is a supernumerary muscle located in the anterior thoracic region, running parallel to the sternum. Different anatomical studies have reported the prevalence of the sternalis muscle to be 1.923.5% (4). It was first shown on mammography by Bradley et al. (5), who described it in six women. Case ReportA forty-eight year old patient was interpreted in our centre for screening mammography. Standard CC and MLO views were obtained and interpreted with previous mammograms. CC mammogram demonstrated a developing density in the medial posterior part of the breast. The density was round in shape and the edges were well defined ( Figure 1). As we interpreted that lesion as a developing density, ultrasound examination was performed. Ultrasonographic views showed approximately 5x35x70 mm muscle tissue over the right pectoralis muscle. The muscle tissue was well

The Importance of Sternalis Muscle in Breast Surgery

“…If doubt still exists, a multidedector CT scan or magnetic resonance imaging (MRI) can confirm the presence of the sternalis muscle. So, unnecessary biopsy of this normal variant can be avoided if one is aware of the entity [12,13].…”