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 Table of Contents  
CASE REPORT
Year : 2017  |  Volume : 2  |  Issue : 2  |  Page : 118-120

Rectus sternalis


Department of Surgical Oncology, Zen Multispeciality Hospital, Mumbai, Maharashtra, India

Date of Submission14-Sep-2017
Date of Acceptance06-Nov-2017
Date of Web Publication15-Dec-2017

Correspondence Address:
Dr. Tanveer Abdul Majeed
Department of Surgical Oncology, Zen Multispeciality Hospital, Mumbai, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/bjhs.bjhs_24_17

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  Abstract 


The sternalis muscle is an uncommon variant of the anterior thoracic chest wall musculature. During mastectomy of a patient, we observed a left-sided unilateral vertical band of texture sternalis muscle fiber overlying the lateral edge of the sternum. We are reporting about the same in this case. The origin of this muscle is a debatable topic. It can be misdiagnosed by the clinicians on a routine mammography. The presence of this muscle can cause alterations in electrocardiography during investigation.

Keywords: Mammography, mastectomy, rectus sternalis muscle


How to cite this article:
Sarodaya VR, Majeed TA. Rectus sternalis. BLDE Univ J Health Sci 2017;2:118-20

How to cite this URL:
Sarodaya VR, Majeed TA. Rectus sternalis. BLDE Univ J Health Sci [serial online] 2017 [cited 2020 Aug 13];2:118-20. Available from: http://www.bldeujournalhs.in/text.asp?2017/2/2/118/220943



The sternalis muscle is an uncommon anatomical variant of the anterior thoracic region musculature which is well documented. It is familiar to anatomists but quite unknown among clinicians and radiologists.[1] The incidence of rectus sternalis is about 3%–6%.[2] It has different nomenclatures, namely, musculus sternalis, presternalis, sternalis muscle, sternalis brottrum, or thoracis.[3],[4] Unilateral occurrence is the most common.[5] Embryologically, this accessory muscle is derived from myotonic hypomeres, which form the muscles of the ventral and lateral body walls in the thorax and abdomen.[6] It represents a remnant of panniculus carnosus present in quadruplets.[7] The muscle usually arises from the upper sternum and the infraclavicular region and gets inserted into various points such as the pectoral fascia, lower ribs, costal cartilages, rectus abdominis muscle sheath, or the abdominal external oblique muscle aponeurosis.[8],[9] It is innervated by perforating branches of the intercostal nerves and its vascular supply comes from perforating branches of the anterior intercostal arteries.[10] We here by present a case associated with “rectus sternalis” muscle.


  Case Report Top


A 65-year-old postmenopausal woman presented with a lump in her right breast of 2-month duration. Her obstetric score was G3P2A1L2. She was a known diabetic for 10 years but well controlled on oral hypoglycemic agent. On examination, the right breast showed nipple retraction and minimal peau d' orange. Her ultrasonography (USG) breast revealed a mass lesion measuring 4 cm × 3 cm × 2 cm in the central quadrant of the right breast with subcentimeter axillary nodes. Chest X-ray and mammogram showed a 4.0 cm × 3.0 cm × 2.0 cm spiculated lesion in central quadrant with clustered microcalcification and architectural deformity [Figure 1]. On physical examination, a 4 cm × 3 cm × 3 cm mass was palpated in the central quadrant of the right breast which was freely mobile with no tethering or fixity to pectoralis major. Core needle biopsy was confirmatory of infiltrating duct carcinoma. Her USG abdomen, chest X-ray, and bone scan were normal. She was diagnosed as locally advanced breast carcinoma with T4aN1M0. She received three cycles of neoadjuvant CEF regimen (cyclophosphamide, epirubicin, 5-fluorouracil) followed by response evaluation. In view of good response, she was planned for the right radical mastectomy with axillary dissection and she underwent the same. Intraoperatively, we found a vertical band of muscle fiber overlying the lateral edge of the sternum and getting inserted into the deep fascia of the neck, and lower insertion was on the anterior part of rectus sheath, which represented “rectus sternalis” muscle [Figure 2].
Figure 1: (a) Cranial-caudal view. (b) Mediolateral-oblique view. Bilateral mammogram right breast showing architectural distortion and stippled microcalcification (white arrow) and pectoralis major muscle (black arrow)

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Figure 2: A unilateral strip of rectus sternalis muscle. (PM: Pectoralis major, RS: Rectus sternalis)

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  Discussion Top


The rectus sternalis muscle is occasionally present in the pectoral region in human beings but regularly seen in lower animals.[11] The incidence of this muscle varies with race, ethnicity, and sex, Asians 11.5%, Africans 8.4%, Indians 4.8%, and Europeans 4.4%.[6] It is unilateral or bilateral.[12] Patients diagnosed with rectus sternalis muscle are usually asymptomatic.[13]

The first reported literature pertaining to sternalis muscle was done by Cabrollius (1604), but its formal description was done only in 1776 by Dupuy. There are various postulations about its origin: (a) pectoralis major; (b) rectus abdominis; (c) sternocleidomastoideus; (d) panniculus carnosus, which is more developed in lower animals.[10] Panniculus carnosus is a subcutaneous muscle such as platysma which is very prominent in dogs and is responsible for wrinkling the trunk skin.[10] It is believed that the defective precursor migration of the prepectoral mass which gives rise to the pectoralis major and minor muscles may also contribute to the sternalis muscle development while mechanical disturbances may lead to atypical clockwise rotation of the muscle fibers.[14],[15] It gets inserted into rectus sheath, costal cartilage, or lower ribs and is situated between anterior thoracic superficial fascia and pectoral fascia.[16]

Intercostal nerves and the anterior thoracic cutaneous nerves provide the sternalis muscle's innervation.[10] The arterial supply of this muscle is from perforating branches of the internal thoracic artery. The contraction of this muscle can elevate the lower part of the chest because of its superficial location. Thus, it plays only an accessory role in lower chest wall elevation.[12],[17] However, there are no reports that suggest it acts as an accessory muscle of respiration.

Magnetic resonance imaging accurately defines the rectus sternalis as a flat structure that runs parallel to the overlying pectoralis major muscle.[12]

Usually, patients with rectus sternalis are asymptomatic however:

  1. The presence of pectoralis major muscle can cause alterations in electrocardiography during investigation [12],[18]
  2. During routine mammography, sternalis muscles can be mistaken for a tumor in the craniocaudal view during initial investigation or as a recurrence during follow-up in the postoperative period.[12],[19]


Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Bailey PM, Tzarnas CD. The sternalis muscle: A normal finding encountered during breast surgery. Plast Reconstr Surg 1999;103:1189-90.  Back to cited text no. 1
    
2.
Loukas M, Bowers M, Hullett J. Sternalis muscle: A mystery still. Folia Morphol (Warsz) 2004;63:147-9.  Back to cited text no. 2
    
3.
Sadler TW. Langmans Medical Embryology. 9th ed. Baltimore: Lippincott Williams & Wilkins; 2004.  Back to cited text no. 3
    
4.
O'Neill MN, Folan-Curran J. Case report: Bilateral sternalis muscles with a bilateral pectoralis major anomaly. J Anat 1998;193:289-92.  Back to cited text no. 4
    
5.
Bharathi D, Sarala HS, Padmalatha N, Balakrishna. Morphology of rectus sternalis: A cadaveric study. Int J Life Sci Res 2014;2:65-7.  Back to cited text no. 5
    
6.
Mehta V, Arora J, Yadav Y, Suri RK, Rath G. Rectus thoracis bifurcalis: A new variant in the anterior chest wall musculature. Rom J Morphol Embryol 2010;51:799-801.  Back to cited text no. 6
    
7.
Barlow RN. The sternalis muscle in American whites and Negroes. Anat Rec 1935;64:413-26.  Back to cited text no. 7
    
8.
Raikos A, Paraskevas GK, Yusuf F, Kordali P, Ioannidis O, Brand-Saberi B, et al. Sternalis muscle: A new crossed subtype, classification, and surgical applications. Ann Plast Surg 2011;67:646-8.  Back to cited text no. 8
    
9.
Georgiev GP, Jelev L, Ovtscharoff VA. On the clinical significance of the sternalis muscle. Folia Med (Plovdiv) 2009;51:53-6.  Back to cited text no. 9
    
10.
Silveira D, Sousa LM, Siqueira SL, Oliveira BVM, Silva AT, Costa JP, et al. Sternalis muscle: An anatomic variation of the anterior chest wall. J Morphol Sci 2012;29:76-8.  Back to cited text no. 10
    
11.
Katara P, Chauhan S, Arora R, Saini P. A unilateral rectus sternalis muscle: Rare but normal anatomical variant of anterior chest wall musculature. J Clin Diagn Res 2013;7:2665-7.  Back to cited text no. 11
    
12.
Raikos A, Paraskevas GK, Tzika M, Faustmann P, Triaridis S, Kordali P, et al. Sternalis muscle: An underestimated anterior chest wall anatomical variant. J Cardiothorac Surg 2011;6:73.  Back to cited text no. 12
    
13.
Scott-Conner CE, Al-Jurf AS. The sternalis muscle. Clin Anat 2002;15:67-9.  Back to cited text no. 13
    
14.
Kida MY, Izumi A, Tanaka S. Sternalis muscle: Topic for debate. Clin Anat 2000;13:138-40.  Back to cited text no. 14
    
15.
Paraskevas GK, Raikos A. Bilateral pectoral musculature malformations with concomitant vascular anomaly. Folia Morphol (Warsz) 2010;69:187-91.  Back to cited text no. 15
    
16.
Jelev L, Georgiev G, Surchev L. The sternalis muscle in the Bulgarian population: Classification of sternales. J Anat 2001;199:359-63.  Back to cited text no. 16
    
17.
Bhat KM, Potu BK, Gowda S. Sternalis muscle revisted in South Indian male cadaver: A case report. Cases J 2009;2:6318.  Back to cited text no. 17
    
18.
Cherian SB, Gandhalam AJ. Rectus sternalis muscle: An anatomical variant of anterior chest wall. OA Anatomy 2014;2:16.  Back to cited text no. 18
    
19.
Vaithianathan G, Aruna S, Rajila RH, Balaji T. Sternalis “mystery” muscle and its clinical implications. Ital J Anat Embryol 2011;116:139-43.  Back to cited text no. 19
    


    Figures

  [Figure 1], [Figure 2]



 

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