A perceived “gap” in the center of the chest usually refers to one of two anatomical features: the space between the breasts (the intermammary cleft) or a depression in the bony structure of the chest wall. This space or indentation is typically a harmless manifestation of normal human variation. While often related to soft tissue distribution, a noticeable depression can occasionally point to an underlying structural difference. Understanding the specific cause helps determine if it is a natural feature or requires medical attention.
Normal Anatomical Variation
The most frequent reason for a visible separation or gap between the breasts is the natural placement and distribution of soft tissue over the sternum, or breast bone. The sternum forms the central boundary of the chest, and the breasts rest on the pectoralis major muscles that attach to this bone. The intermammary cleft, the natural groove separating the breasts, exists because the breast tissue does not fuse across the midline.
The appearance of this gap is highly variable, influenced by factors like tissue density, subcutaneous fat, and genetics, which dictate where the breast base begins and ends. The distance between the pectoralis major muscles at the sternum commonly ranges from one to three centimeters, reflecting normal genetic variation in muscle and chest shape. Natural asymmetry also plays a role, as one breast is often slightly larger or positioned differently, affecting how the central space appears. These variations in soft tissue and bony structure are simply a reflection of normal human diversity and typically present no health concerns.
Understanding Structural Causes
When the perceived gap is a true structural depression in the bony chest wall, it is often due to a congenital condition known as Pectus Excavatum, or “funnel chest.” This is the most common chest wall deformity, affecting approximately 1 in 400 individuals, and it results in the sternum and surrounding rib cartilage growing inward. The condition is thought to be caused by the abnormal growth of the costal cartilage that connects the ribs to the breast bone. While the exact cause is not fully known, it often runs in families and can be associated with connective tissue disorders like Marfan syndrome.
The appearance of Pectus Excavatum varies widely, ranging from a mild cosmetic indentation to a severe, deep concavity that may be symmetrical or asymmetrical. This structural abnormality can become more pronounced during rapid growth periods, such as puberty. In severe cases, the inward pressure on the chest cavity can displace or compress the heart and lungs, leading to functional impairment. While many patients remain asymptomatic, the condition can cause decreased exercise tolerance and a restrictive pattern in pulmonary function tests.
Postural and Muscular Influences
Beyond fixed skeletal variations, the appearance of a chest gap or depression can be temporarily influenced by modifiable factors like posture and muscle development. Poor posture, particularly a tendency toward a hunched or rounded upper back, known as thoracic kyphosis, can make the sternal area appear more recessed. This slouching posture compresses the chest cavity and causes the shoulders to roll forward, which visually exaggerates the appearance of a sunken chest.
Postural kyphosis is the most common form and often develops during adolescence. Correcting this alignment can immediately minimize the perceived depth of the gap. The development of the pectoral muscles also plays a role in the overall contour of the chest wall; a lack of muscle development or an imbalance can contribute to a sunken appearance. Engaging in exercises that strengthen the core and back muscles can help support better posture and improve the overall chest alignment.
When Medical Evaluation Is Necessary
While most variations in the chest are harmless and purely cosmetic, a medical evaluation becomes necessary if the chest gap or depression is accompanied by certain functional symptoms. These signs suggest that the underlying structural issue may be severe enough to affect the heart or lungs. A person should seek professional advice if they experience persistent shortness of breath, especially during physical exertion, or a noticeable decrease in exercise tolerance.
Other concerning symptoms include unexplained chest pain, a rapid heartbeat, or palpitations, as the inward sternum can sometimes compress the heart. An evaluation is also warranted if the depression appears to be rapidly worsening or is associated with other conditions, such as scoliosis or a connective tissue disorder. The physical and psychological impact of a chest wall deformity is a valid reason for consultation, even if functional symptoms are mild. A healthcare provider may use imaging tests, such as a computed tomography (CT) scan, to measure the severity and assess any potential impact on internal organs.