The sternalis muscle: an unusual normal finding seen on mammography

Bilateral Sternalis Muscles: The Clinical Significance of This Rare Discovery

This case report explores the physical characteristics and clinical significance of the sternalis muscle, an uncommon anatomical variation of the anterior thoracic wall. If present, the sternalis muscle may distort diagnostic images and can be associated with incorrect interpretation of such medical images, misdiagnoses, and even surgical complications. As such, enhancing clinicians' knowledge of this muscle and improving its recognition is of the utmost importance. In this case report, a rare bilateral sternalis muscle that was discovered during an educational human cadaveric dissection of a 73-year-old Black male is described. The right sternalis muscle fibres extended from the mid-sternal level to the right sternocostal arch, measuring 11.5 cm in length and 3.4 cm at its largest width. In contrast, the smaller left sternalis muscle fibres measured only 5.6 cm in length and 1.2 cm at its greatest width. This rare bilateral presentation of the sternalis muscle is documented in approximately one-third of all reported sternalis cases with an associated estimated prevalence as low as 1.7% among the general population. Serving as a reminder of the intricate anatomical complexities that continue to challenge and intrigue medical professionals, this report advocates for continued education of anatomical variations to enhance patient care and medical practices.

Bilateral Sternalis Muscle With the Absence of Unilateral Sternocostal Part of the Pectoralis Major and Variation of Pectoralis Minor Muscles

This study aims to report a 57-year-old male cadaver with a rare muscular variation of the sterno-pectoral region. An unusual sternalis muscle was observed on both sides, arising from the external oblique muscle aponeurosis. The fibers converged upwards and medially in a curved course, producing a bundle 99.50 mm long on the right side and 74.60 mm on the left. The muscles on both sides were supplied by the second, third, and fourth intercostal nerves. In the right pectoralis major (PM) muscle, the sternocostal head was completely absent, and the clavicular head arose from the medial two-thirds of the clavicle, whereas abdominal fibers arose from the aponeurosis of the external abdominal oblique muscle and ran upward and laterally and joined the clavicular fibers with a wide triangular gap. On the left side, there was an anatomically normal PM muscle. The origin of the pectoralis minor was unusually high on both sides. The morphological variations of sterno-pectoral musculature have significant implications for clinical practice, which allows more precise surgical or radiological outcomes. Clinicoradiological evaluation of these variations is important to achieve appropriate dissection planes during chest wall surgery.

Variations in the anterior thoracic wall with sternalis muscle and accessory pectoralis major muscle

PURPOSE

The new type of the sternalis muscle needs to be recognized, and the accessory pectoralis major muscle (AcPM) was found between the pectoralis major and minor muscle. It needs to be acknowledged those two different variations can exist in one case.

METHODS

The muscle was found on a 73-year-old male cadaver during the dissection class for the anterior thoracic wall. It was proceeded to identify the adjacent structures with precise dissection.

RESULTS

The cadaver had sternalis muscle bilaterally. Both side sternalis muscles had a medial and lateral belly and attached to pectoral fascia and rectus abdominis sheath. The pectoralis major muscle (PMaj) had a more profound slip attached to the costal cartilage of rib 4 and 5, which is AcPM. The pectoral nerve traveled through the clavipectoral fascia to the AcPM and through PMaj to the sternalis muscle.

CONCLUSIONS

This study presented a new type of sternalis muscle. Two different variations were developed along with the pectoral nerve. It needs to be recognized in the diagnostic images, the muscle rehab outcome, and the surgical complication.

Bilateral sternalis muscle in a Sudanese cadaver

Introduction and importance

Sternalis/rectus sterni is a rare muscle found in the anterior chest wall, it occurs in 35% of humans. The early detection of its presence is critical in regular mammogram screening in order to avoid possible differential diagnostic dilemma.

Case presentation

We report here a case of the sternalis muscle observed bilaterally, it was found during routine dissection session of an elderly male cadaver in the dissection room, Faculty of Medicine, University of Khartoum.

Clinical discussion and conclusion

Sternalis muscle is a familiar entity to anatomists, but can pose a diagnostic and surgical dilemma to some clinicians. Presence of the muscle can be confusing in regular mammogram screening and CT and MRI should be utilized to clear the dilemma, and further evidence needs to be explored and studied.

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Sternalis/rectus sterni is a rare muscle found in the anterior chest wall, it occurs in 3-5% of humans.

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We report here a case of the sternalis muscle observed bilaterally, it was found during a routine dissection session of an elderly male cadaver in the dissection room, Faculty of Medicine, University of Khartoum.

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Presence of the muscle can be confusing in regular mammogram screening and CT and MRI should be utilized to clear the dilemma, and further evidence needs to be explored and studied.

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Considering its insignificant function, it could be used as a muscle flap in surgical reconstructions of the head, neck, chest wall and breast.

The prevalence and distribution of sternalis muscle: a meta-analysis of published literature of the last two hundred years

The sternalis muscle (SM) is an anatomical variant that lies subcutaneously and is superficial to the pectoralis major muscle or sternum. The present meta-analysis was conducted to analyze the prevalence, anatomical features, and variance of the SM in different population. In total, 98 studies were included for this meta-analysis. Eighty-two studies dealt with adult subjects, and sixteen studies with fetuses. The worldwide prevalence of SM was observed to be 6% or 0.06 [0.05-0.7, 95% CI] in 27,470 adults, whereas it was 0.29 [0.20-0.39, 95% CI] in 673 fetuses. In 259 anencephalic fetuses, the prevalence was 44% or 0.44 [0.26-0.63, 95% CI], while the same in 414 fetuses without anencephaly was 16% or 0.16 [0.06-0.27, 95% CI]. The reported prevalence rate in Asian mongoloid population (9.1% = 0.091) was three times that of the Asian Caucasian population (3.33% = 0.0333). The prevalence in European descent was 3.93%. Interestingly, the reported prevalence rates in North and South American populations were 3.44% and 3.66%, almost being equivalent. The cadaveric investigations revealed that the SM had an overall prevalence of 5.96% in adults based on 76 studies, which was higher than other modalities of investigations. The multi-detector computerized tomography (MDCT) had shown the prevalence of approximately 4.33%. The same was reported in surgical studies and mammographic studies as 0.47% and 0.02%, respectively. The SM is not an unusual variant of the chest wall musculature. MDCT could be a new method to precisely demonstrate the morphology, course, and size of the SM in vivo.

Sternalis muscle in jordanian population: a prevalence study and level of physicians' awareness

Sternalis muscle (SM) is an anatomical variant that lies parallel to the sternum. It is present in (8%) of human population. Awareness about its presence during thoracic imaging is important, since it might be misdiagnosed as a tumor. This study is the first that discusses the prevalence of SM in the Jordanian population and document the level of awareness about SM among intern doctors and surgery and radiology residents. Our aims are to know the prevalence of SM in the Jordanian population, using thoracic multi-detector computerized tomography (CT) images, and to assess the awareness about SM among a sample of intern and resident Jordanian physicians. Random anonymous axial thoracic multi-detector CT images of 1,709 (801 females and 908 males) Jordanian patients, were examined for the presence or absence of unilateral and/or bilateral SM. A questionnaire aiming to identify SM was distributed among 175 intern doctors, 26 surgery resident and 28 radiology resident doctors, their answers were summarized. The prevalence of SM among Jordanians is 5.9%. The prevalence of unilateral SM is 2.1% on the right side of the thorax and 1.9% on the left side, bilateral prevalence was 1.8%. While 35.7% of the radiology residents could identify SM using CT and/or anatomy images, only 3.9% of surgery residents and none of the intern doctors could. We concluded that SM is present in the Jordanian population, with a prevalence of 5.9% which falls within the global average. Intern doctors and surgery and radiology residents are almost unaware and unfamiliar about SM.

Evidence of the sternalis muscle in two South African cadavers

The sternalis muscle is an infrequent, non-pathological anatomical variant typically misrepresented in a clinical context. It presents with 3-8% prevalence, according to cadaveric studies. The muscles were identified during routine cadaver prosection at the School of Anatomical Sciences, University of the Witwatersrand. Here, we report two cases of the sternalis muscle in two South African White cadavers. Analysis of the sternalis muscles revealed unilaterally present, distinctly defined muscle masses on the right (case number 1, female) and left (case number 2, male) hemithorax, lateral to the sternum. The muscles occurred with a prevalence of 2.25% within the cadaveric population examined. The prevalence of the sternalis muscle is generally low, especially in the European population. Their presence represents the remnants of the cutaneous muscles in the ventral thorax of lower animals. Clinically, the sternalis muscle may be misinterpreted as a pathological mass or lesion, thus accurate knowledge regarding its variations and prevalence is of importance.

Improvement in Existing Chest Wall Irregularities During Breast Reconstruction

Mastectomies for both cancer resection and risk reduction are becoming more common. Existing chest wall irregularities are found in these women presenting for breast reconstruction after mastectomy and can pose reconstructive challenges. Women who desired breast reconstruction after mastectomy were evaluated preoperatively for existing chest wall irregularities. Case reports were selected to highlight common irregularities and methods for improving cosmetic outcome concurrently with breast reconstruction procedures. Muscular anomalies, pectus excavatum, scoliosis, polythelia case reports are discussed. Relevant data from the literature are presented. Chest wall irregularities are occasionally encountered in women who request breast reconstruction. Correction of these deformities is possible and safe during breast reconstruction and can lead to improved cosmetic outcome and patient satisfaction.

Two Cases of Rectus Sternalis Muscle

The sternalis muscle, an uncommon anatomical variant of the chest wall musculature, though perhaps well known to anatomists, is quite unfamiliar to clinicians and radiologists despite attempts to highlight its clinical importance in recent years. During routine dissection for undergraduate medical teaching, in the department of anatomy, we came across two cases of sternalis muscle. The first was a unique case of unilateral right sternalis with contralateral insertion on the left sternocleidomastoid, and the second case where bilateral presence of the muscle was noted with ipsilateral insertion. The former was supplied by medial pectoral nerve and the latter by lower intercostal nerves. Usually present between the pectoral and superficial fasciae, wide ranging prevalence and morphology have been attributed to this muscular variant. Opinions differ on its development and nerve supply. Its presence can be misdiagnosed as a wide range of benign and malignant anterior chest wall lesions and tumours, but it is also of great use as a pedicle flap or flap microvascular anastomosis in reconstructive surgeries of anterior chest wall, head and neck and breast. In this paper, two cases of sternalis muscle which presented very differently from each other are discussed.

Sternalis muscle, what every anatomist and clinician should know

The sternalis muscle is a well documented but rare muscular variation of the anterior thoracic wall. It lies between the superficial fascia and the pectoral fascia and is found in about 8% of the population. It presents in several morphological variants both unilaterally and bilaterally and has no apparent physiological function. There is still much disagreement about its nerve supply and embryological origin. With the advent of medical imaging and thoracic surgery the clinical importance of this muscle has been re-emphasized. It has been implicated in misdiagnosis of breast masses on routine mammograms owing to its parasternal location and relative unfamiliarity among radiologists. When undetected before any thoracic surgery, it has the potential to interfere with and prolong such procedures. When present and detected preoperatively it can be used as a muscular flap in reconstructive surgeries of the breast and neck. This article will present the sternalis muscle with special emphasis on its morphology, homology, and clinical significance.

Prevalence and variance of the sternalis muscle: a study in the Chinese population using multi-detector CT

OBJECTIVE

To analyze the prevalence, anatomical features, as well as variance of the sternalis muscle in the Chinese population using multi-detector computed tomography (MDCT).

METHODS

We retrospectively reviewed 6,000 adult axial MDCT images to determine the overall and gender prevalence of the sternalis muscles. We also analyzed the side prevalence and anatomical features, including shape, size, location and course.

RESULTS

The sternalis muscle was present in 347 (5.8 %) of 6,000 adults. This muscle was more common in males (6.0 %, 187/3091) than in females (5.5 %, 160/2909). Among the 347 adults, 118 (34.0 %) had bilateral sternalis muscles; 148 (42.7 %) had right sternalis muscles; and 81 (23.3 %) had left sternalis muscles. The sternalis muscle was either flat or nodular and located superficial to the major pectoral muscles on CT axial transverse images. According to the muscle morphology and course, we classified sternalis muscles as three different types and nine subtypes. The muscles appeared with a single head and single belly in 58.5 %, double or multiple heads in 18.1 %, and double or multiple bellies in 23.4 %. The mean length, width and thickness were 111.1 ± 33.0, 17.7 ± 9.9 and 4.1 ± 1.7 mm measured on MDCT.

CONCLUSION

The sternalis muscle was highly prevalent in normal Chinese adults. MDCT is an effective method to demonstrate this muscle in vivo.

Biceps sternalis: a Y-shaped muscle on the anterior chest wall

The sternalis muscle is an accessory muscle located in the anterior thoracic region, which is relatively unfamiliar to clinicians and surgeons. To date, no data from the Iranian population have been published. Here, a rare case of a sternalis muscle is presented. In addition, this anomalous muscle was observed along with other visceral and vascular anomalies. This case is unique and provides significant information to radiologists, angiologists and surgeons seeking to apply safer interventions. It is also imperative for better interpretation of mammographic images and in reconstructive surgery.

The sternalis muscle: radiologic findings on MDCT

PURPOSE

The purpose of this study was to characterize and determine the prevalence of the sternalis muscle using 64-row multidetector computed tomography (MDCT).

MATERIALS AND METHODS

We retrospectively reviewed MDCT chest scans that were performed in a hospital during the course of a month. The study population consisted of 948 consecutive patients (511 males and 467 females). On the MDCT scans the sternalis muscle was defined as the longitudinal muscle lying on and superficial to the pectoralis major muscle.

RESULTS

The prevalence of the sternalis muscle was 10.5 %. The muscle was present more frequently in females (13.0 %) compared to males (8.4 %) (P = 0.02). In the majority of patients, the muscle was located longitudinally in the parasternal position; however, in two patients it was positioned across the sternum. One hundred twenty were flat types, while the remaining five had oblique shapes. The muscle mean height, width and depth were 77.9 ± 25.1, 19.4 ± 12.2 and 2.8 ± 1.3 mm, respectively. The muscle was wider in males compared to females (P < 0.001).

CONCLUSION

Using MDCT, its prevalence was shown to be 10.5 %. This variant muscle can be differentiated from other pathological structures using its specific characteristic appearance.

Sternalis muscle: an underestimated anterior chest wall anatomical variant

Over the recent years, an increased alertness for thorough knowledge of anatomical variants with clinical significance has been recorded in order to minimize the risks of surgical complications. We report a rare case of bilateral strap-like sternalis muscle of the anterior chest wall in a female cadaver. Its presence may evoke alterations in the electrocardiogram or confuse a routine mammography. The incidental finding of a sternalis muscle in mammography, CT, and MRI studies must be documented in a patient's medical records as it can be used as a pedicle flap or flap microvascular anastomosis during reconstructive surgery of the anterior chest wall, head and neck, and breast. Moreover, its presence may be misdiagnosed as a wide range of benign and malignant anterior chest wall lesions and tumors.

Sternalis muscle revisted in South Indian male cadaver: a case report

Introduction

Sternalis/rectus sternalis is a rare muscle found in the chest wall. Only 3-5% of the cases are found world wide.

Case presentation

Here we report the case of Sternalis in the 60-year-old South Indian male cadaver. This report discusses the origin, orientation, relations of this muscle.

Conclusion

Importance of the knowledge of the presence of these rare muscles in clinical diagnosis and therapeutic implications is discussed.

Use of the rectus sternalis in augmentation mammoplasty: case report and literature search

Breast augmentation is by far one of the most common aesthetic procedures currently performed by plastic surgeons. The plane of dissection for prosthesis placement is quite often partial submuscular. The rectus sternalis, an nomalous muscle, may interfere with the submuscular pocket dissection when an intraalveolar or submammary approach is used. The use of this muscle to cover the prosthesis in its most medial part is presented.

The Sternalis Muscles

OBJECTIVE

We studied the incidence and appearance of the sternalis muscles on multidetector computed tomography (MDCT) to permit the differentiation of the sternalis from significant pathologic condition.

METHODS

We retrospectively evaluated consecutive contrast-enhanced 16 row MDCT scans of the chest obtained in 1387 Korean patients (790 males and 597 females) between September 2003 and January 2005. All computed tomography scans were obtained in the supine position. Age ranges were 16 to 87 years and average was 59.2 years. Imaging analysis was based upon distribution (unilateral or bilateral, size, shape, and location). Statistical differences were evaluated by chi tests and Independent Samples t tests.

RESULTS

The sternalis muscle was present in 86 (6.2%) of 1387 patients. This muscle was more common in female (44 of 597, 7.3%) than in male (42 of 790, 5.3%) patients, but statistical significance was not noted (P=0.058). Twenty-three patients showed bilateral sternalis muscles. Among 63 patients with unilateral sternalis muscles, 28 patients showed left sternalis muscles and 35 patients showed right sternalis muscles. Unilateral distribution was more common. The height, AP diameter, and width of the sternalis muscle were not significantly different between unilateral and bilateral muscles (P=0.182, 0.911, and 0.114, respectively). The height and AP diameter showed no significant difference between male and female (P=0.470, 0.329, respectively) patients, but the width was wider in male (P<0.001) patients. All sternalis muscles showed flat appearance, except for 1 case. The sternalis muscles were located longitudinally in parasternal position in all cases.

CONCLUSIONS

The sternalis muscle is an unusual normal variant of the chest wall musculature running parallel to the sternum with various sizes and most sternalis muscles are flat on MDCT. Unilateral distribution is more common, and the size of muscle is larger in males. Its incidence is 6.2% in Korean population. Radiologists should be familiar with the image findings of the sternalis muscle to avoid any confusing pathologic lesions and facilitate its clinical use such as flap.

[Sternalis muscle in breast surgery]

The sternalis muscle is a normal anatomic variant, which exists in about 5 to 8% of people. It runs longitudinally superficial to pectoralis major, alongside the sternum. Although the sternalis seems common in cadaveric studies, physicians are not familiar with it, which may lead to confusion in diagnosis. Occasionally, the sternalis may be misinterpreted as a breast mass on mammogramm. In that case, computed tomography and magnetic resonance imaging are useful. We report herein two cases of sternalis muscles encountered during mastectomy.

The Conjoined Sternalis-Pectoralis Muscle Flap in Immediate Tissue Expander Reconstruction After Mastectomy

The sternalis muscle is an accessory muscle of the anterior chest wall. This is a rare anatomic variant reported in approximately 8% of the population, with variation among races. While several anatomic studies of the sternalis muscle exist, nothing in the literature addresses the implications of this muscle on reconstruction of the breast after mastectomy. Based on several encounters of this muscle variant by the senior author over a 15-year period, we offer a strategy and rationale for dealing with this rare, but known, anatomic variant during immediate tissue expander reconstruction of the breast after mastectomy. First is the importance of recognizing the presence of a sternalis muscle, which may present in a variety of configurations. We offer our technique of conjoined sternalis-pectoralis muscle flap during tissue expander reconstruction of the breast. This allows for the creation of a larger, more properly placed submuscular pocket with adequate muscle coverage of the tissue expander. Our experience illustrates that the reconstructive surgeon must be familiar with the sternalis muscle and be prepared to adapt his or her technique for tissue expander placement when faced with this accessory muscle.

The normal breast and its variations in mammography

The mammographic appearance of the breast varies along the lifetime due to physiological modifications or use of hormonal therapies. Density of the glandular tissue is due to amount of cellular elements of the gland and to hydratation of the tissues. Normal variations are encountered as for example breast asymmetry. The currently breast composition should be described with the BI-RADS lexicon classification. Mammary asymmetry is frequent and has to be differentiated from pathologic changes. A good mammographic technique is mandatory for an adequate visualisation of the breast tissues.

Sonography of the thoracic and abdominal walls

Pathologic processes that may involve the thoracic or abdominal wall occasionally raise diagnostic challenges because of the low specificity of physical findings. Congenital and developmental anomalies may mimic soft-tissue or bone tumors; tumors may mimic inflammatory and infectious diseases, and vice versa. Furthermore, these disorders may produce remote manifestations that are frequently misdiagnosed as visceral pain. Many of these parietal processes have typical sonographic appearances that allow definitive diagnosis. This article reviews characteristic sonographic appearances of thoracic and abdominal wall disorders. Familiarity with these sonographic features facilitates accurate diagnosis and optimal patient treatment.

Left musculus sternalis

During routine dissection in the Morphological Sciences Department II of the Universidad Complutense de Madrid, the presence of a sternalis muscle was observed in the left hemithorax of a 70-year-old male cadaver. We report on its position, relationships, and innervation, as well as its clinical relevance, indicating some guidelines for its physical examination. We also present a brief overview of the existing literature regarding the nomenclature, historical reports, and incidence of this muscle.

Variants of sternal insertion of the pectoral muscle on mammography: a pictorial review

The aim of this pictorial review is to demonstrate the diverse presentations of the medial insertion of pectoralis major on mammography. A collection of cases demonstrating the variations in appearance of this muscle insertion are presented. The factors contributing to the appearances of this artifact, the differential diagnoses and useful further investigations are discussed. Familiarity with the different presentations of this muscle insertion will facilitate recognition and prevent unnecessary investigations.