A dent in the armpit, or axilla, is a change in the normal surface contour of the skin and underlying tissues. Noticing any alteration often leads to concern. The axilla is a complex area, housing a variety of muscles, fat, lymph nodes, and blood vessels. A dent can arise from natural body structure or changes resulting from past medical events. Understanding the typical causes helps determine whether the dent is a harmless feature of your anatomy or if a medical evaluation is warranted.
The Role of Normal Anatomy
The structure of the axilla is complex, and variations in its components can easily create the appearance of an indentation without any underlying medical issue. The boundaries of the armpit are formed by large muscle groups: the Pectoralis major muscle in the front and the Latissimus dorsi muscle in the back. These muscles create the familiar anterior and posterior axillary folds, and the space between them can naturally appear recessed or dented, particularly in leaner individuals.
The distribution of subcutaneous adipose tissue, or body fat, also plays a significant role in the armpit’s visible shape. A reduction in overall body weight can lead to a decrease in the axillary fat pad, making the space between the muscle folds more pronounced. Furthermore, lifting the arm stretches the skin and soft tissues, which can temporarily exaggerate a natural depression or crease. These anatomical contours are generally symmetrical and are not considered pathological.
Scars and Chronic Skin Issues
Permanent indentations in the armpit are frequently the result of past damage to the skin and underlying connective tissue from chronic dermatological conditions. The armpit is a high-friction area prone to inflammation, which can lead to scar tissue formation that pulls the skin inward.
One such condition is Hidradenitis Suppurativa (HS), a long-term inflammatory skin disease. HS involves repeated blockage and rupture of hair follicles, leading to painful, boil-like lumps and abscesses deep beneath the skin. As these inflammatory lesions heal, they form dense, fibrous scar tissue, sometimes creating tunnels, or sinus tracts. This extensive scarring is often atrophic, meaning it is indented or pitted, permanently altering the skin’s texture. Similarly, an older, deep infection or a severe cyst that required drainage can cause a localized area of retraction as the scar tissue contracts.
Underlying Tissue and Post-Surgical Changes
Dents can also be caused by alterations to the tissues beneath the skin’s surface, often resulting from the removal of a mass. A common benign mass in the axilla is a lipoma, a soft, slow-growing tumor composed of fat cells. When a lipoma or a fluid-filled cyst is surgically excised, the removal of this internal volume can leave a temporary void that results in a visible depression in the overlying skin contour.
The body usually attempts to fill this space over time, but a noticeable indentation can persist, especially if the mass was large or located deep within the axilla. Surgical procedures involving the lymphatic system also frequently cause contour changes.
An axillary lymph node dissection, often performed for cancer staging, removes a significant amount of fibrofatty tissue and lymph nodes. This permanently changes the underlying architecture and often results in a permanent depression or concavity. Scar tissue from this surgery can also create a condition called cording, or axillary web syndrome, where tight bands of tissue form, further contributing to the dented appearance.
When to Consult a Doctor
While many armpit dents are harmless anatomical variations or old, stable scars, certain characteristics suggest the need for professional medical evaluation. A doctor should be consulted if the indentation is a new development and is accompanied by other concerning symptoms.
These warning signs include rapid changes in the size or shape of the dent, or if it suddenly becomes painful, red, or warm to the touch. It is also important to seek medical advice if the dent is accompanied by a persistent lump or swelling, especially if that lump is firm and feels fixed in place. Furthermore, if the dent appears alongside systemic symptoms such as unexplained weight loss, night sweats, or a persistent fever, a prompt evaluation is necessary. These additional signs can indicate that the underlying cause is an active medical issue requiring diagnosis and treatment.