Sternalis muscle: importance in surgery of the breast

Abstract

Mastectomy is a commonly performed surgery for carcinoma of breast. During surgery, pectoral fascia is removed and pectoralis major muscle is laid bare. Sternalis is a rare muscle encountered in the subcutaneous plane. We examined the operative records of 1,152 patients who underwent modified radical mastectomies between 1990 and 2000. Patients who underwent conservative breast surgery or radical mastectomy were excluded. Among 1,152 patients who underwent modified radical mastectomy, eight were identified as having sternalis, a subcutaneously placed muscle oriented craniocaudally. The thickness of the muscle varied. The muscle was spared in all patients. Sternalis is a rare muscle in the subcutaneous plane. It should not be mistaken for a mass on mammography. During surgery it is important to be aware of this rare entity and identify the muscle early so that the dissection plane is appropriate. The depth at which internal mammary nodes are irradiated may also vary in the presence of the muscle. In addition, it should not be mistaken for recurrence on follow-up.

Two Cases of Rectus Sternalis Muscle

“…The reported differences in prevalence rates could be due to small sample size or due to the fact that one could easily miss noticing a small ill defined muscle [2]. The prevalence is not well known in India, as hardly any studies have been done on the Indian population except by Harish et al, and Katara P et al, who reported prevalence rates of 0.69% and 3.3% respectively [1,4]. However, there are about ten case reports from India by different authors [5][6][7][8][9][10][11][12][13][14], during the five year period from 2011-2015.…”

“…Identification and recognition of this rare anatomical variant can reduce the chances of misdiagnosis, avoid subsequent diagnostic procedures like biopsies, and also misinterpretation as recurrence at a later date [4]. Sternalis muscle when present can mimic a focal density and its presence can be confirmed by MRI or CT imaging [23].…”

Back to the Debate: Sternalis Muscle

“…Kida & Kudoh (1991) also described an incomplete development of the sternocostal head of the pectoralis major, as was seen in our case. The presence of SM is also associated with anomalies of the skull and adrenal gland (Harish & Gopinath, 2003). The incidence of SM in anencephaly is nearly 50% (Windle), however this may be confounded by the difficulty in observing SM in living humans other than by surgery or soft tissue imaging.…”

“…Authors describe these discoveries as a 'normal finding during breast surgery' or 'not of clinical concern' and note the importance of knowledge of the craniocaudally oriented strap of muscle (Bailey & Tzarnas;Vandeweyer, 1999;Harish & Gopinath). Bailey & Tzarnas encountered 3 patients with SM undergoing mastectomy over a 15 year period, while Harish & Gopinath found SM in 8 out of 1152 patients undergoing radical mastectomy.…”

Importância clínica do músculo esternal e suas variações anatômicas: uma revisão sistemática da literatura

“…Devido à localização paraesternal, em exames de imagem, o músculo pode ser visto como uma nodulação anormal na região da mama e ser confundido com um tumor 1,30 . Para facilitar ou até mesmo permitir a Oliveira LA, Quintana HT, Oliveira F diferenciação do músculo esternal de uma real doença, como um possível tumor, Bradley et al 31 e Kumar et al 5 sugerem o uso concomitante de ressonância magnética, mamografia ou tomografia. Ainda, dependendo da localização, pode haver invasão de tumores mamários nesse músculo, tornando necessária a sua remoção cirúrgica durante mastectomias 4 .…”