Lump on Sternum: Understanding the Xiphoid Process, Other Causes, and When to Seek Help

What is the lump on the sternum called?

The most common anatomical "lump" perceived at the bottom of the sternum is the xiphoid process, a small, cartilaginous projection that typically ossifies and fuses with the sternum body with age.

The Xiphoid Process: Anatomy and Function

The sternum, commonly known as the breastbone, is a flat bone located in the central part of the chest. It plays a crucial role in protecting the heart and lungs and serves as an attachment point for ribs and various muscles. The sternum is composed of three main parts, from superior to inferior:

• Manubrium: The broad, upper part that articulates with the clavicles (collarbones) and the first pair of ribs.
• Body (Gladiolus): The long, flat central portion that articulates with ribs 2 through 7.
• Xiphoid Process: The smallest and most inferior part of the sternum.

What it is: The xiphoid process (pronounced ZY-foyd) is derived from the Greek word xiphos, meaning "straight sword," due to its pointed shape. In early life, it is composed of cartilage. As an individual ages, typically after the age of 40, the xiphoid process gradually ossifies (turns into bone) and often fuses with the body of the sternum. This ossification can sometimes result in a more prominent, harder structure that is easily palpable and may be perceived as a "lump."

Function: Despite its small size, the xiphoid process is an important anatomical landmark and provides attachment points for several key muscles and ligaments, including:

• Diaphragm: The primary muscle of respiration.
• Rectus Abdominis: One of the main abdominal muscles.
• Transversus Abdominis: Another deep abdominal muscle.
• Linea Alba: A fibrous band that runs down the midline of the abdomen.

Its location makes it a critical reference point for medical procedures, such as identifying the lower limit for chest compressions during cardiopulmonary resuscitation (CPR) to avoid injury to internal organs.

Normal Variations and Palpation

The xiphoid process is highly variable in its size, shape, and angle, which contributes to why it might be more noticeable in some individuals than others.

• Shape and Size: It can be pointed, bifid (split into two parts), perforated (having a hole), curved, or angled. Its length can also vary significantly from person to person.
• Angle: In some individuals, the xiphoid process may project anteriorly (forward), making it more prominent and easily palpable through the skin.
• Palpability: It is often easily felt, especially in leaner individuals, when lying down, or during deep exhalation. Its firm, bony, or cartilaginous consistency can naturally feel like a "lump" or "knot."

Understanding these normal anatomical variations is crucial to avoid unnecessary concern when palpating this structure.

Other Potential Causes of a "Lump" on the Sternum

While the xiphoid process is the most common anatomical explanation for a perceived lump at the lower sternum, other conditions can manifest as lumps or swelling on or around the sternum. It is important to be aware of these, especially if the "lump" is accompanied by pain or other symptoms.

• Costochondritis or Tietze Syndrome: These conditions involve inflammation of the cartilage that connects the ribs to the sternum.
  • Costochondritis: Typically causes localized chest pain and tenderness, often without swelling. The pain can be sharp and worsen with movement or deep breaths.
  • Tietze Syndrome: Similar to costochondritis but specifically involves swelling of the affected costal cartilage, which can feel like a lump. It is less common than costochondritis.
• Sternum Fractures: Though relatively uncommon, a fracture of the sternum, usually due to direct blunt trauma (e.g., from a car accident), can cause swelling, pain, and a palpable deformity or "lump."
• Tumors or Cysts: Benign (non-cancerous) or malignant (cancerous) growths can rarely occur on or within the sternum. These might include:
  • Lipomas: Benign fatty tumors that feel soft and movable under the skin.
  • Dermoid Cysts: Congenital cysts that can sometimes present as a lump.
  • Bone Tumors: Primary sternal bone tumors are rare, but the sternum can be a site for metastatic cancer (cancer that has spread from another part of the body).
• Keloids or Scar Tissue: Following trauma, surgery, or even severe acne in the sternal area, raised, firm scar tissue (keloids) can form, which may be perceived as a lump.
• Pectus Deformities: While not typically a "lump," structural deformities of the chest wall like pectus carinatum (pigeon chest, an outward protrusion of the sternum) or pectus excavatum (funnel chest, an inward depression of the sternum) can alter the sternal appearance and be a cause for concern regarding chest shape.

When to Seek Medical Attention

While the vast majority of "lumps" at the bottom of the sternum are simply the normal xiphoid process, it is always prudent to consult a healthcare professional if you notice a new or concerning lump anywhere on your body. Seek medical advice if the lump:

• Is painful or tender to the touch.
• Is accompanied by redness, warmth, or swelling.
• Grows rapidly in size.
• Feels hard, fixed, or irregular.
• Causes difficulty breathing or swallowing.
• Is associated with other systemic symptoms such as fever, unexplained weight loss, or fatigue.

A medical evaluation, which may include a physical examination, imaging (like X-ray, ultrasound, or MRI), or blood tests, can accurately diagnose the cause of the lump and provide appropriate management.

Conclusion

The "lump" commonly felt at the very bottom of the sternum is, in most cases, the normal anatomical structure known as the xiphoid process. Its variability in shape, size, and degree of ossification accounts for why it may be more noticeable in some individuals. While this is typically a benign finding, any new, painful, or rapidly changing lump on the sternum or elsewhere on the body warrants professional medical evaluation to rule out other potential causes and ensure peace of mind.