Most lumps felt on or near the sternum turn out to be harmless, often something as simple as the bony tip of the breastbone itself or a swollen joint cartilage. But the sternum sits at a crossroads of bone, cartilage, muscle, and soft tissue, so the list of possibilities stretches from a normal anatomical feature you never noticed before all the way to infections, benign tumors, and occasionally something more serious. Understanding the common causes and their distinguishing features can help you figure out when to shrug it off and when to see a doctor.
The Xiphoid Process, the Most Common “Lump” That Isn’t One
The sternum has three parts: a broad upper section called the manubrium, the long middle body, and a small piece of cartilage at the very bottom called the xiphoid process. In many people the xiphoid points slightly forward, and if you press on the lower end of your breastbone you can feel it as a firm, movable bump right where the ribs meet in the center. It is completely normal anatomy, yet people discover it for the first time and panic, convinced something has grown there.
The xiphoid comes in a surprising range of shapes. It can be broad or thin, forked into two or even three prongs, curved backward, or angled forward enough to push against the skin. Some xiphoid processes contain small holes. These variations are well documented and are occasionally mistaken for masses in the upper abdomen or lower chest wall during physical exams or imaging studies.1PubMed Central. Xiphoid Process Variations: A Review with an Extremely Unusual Case Report If the bump you feel is right at the bottom of the sternum, in the soft triangle where the lower ribs converge, and it feels like bone, there is a good chance you are simply feeling your own xiphoid. A doctor can confirm this in seconds with a quick exam.
Tietze’s Syndrome
If the lump is higher up on the sternum and is tender or painful, one of the likeliest culprits is Tietze’s syndrome. This is a benign, self-limiting condition where one of the cartilage joints connecting a rib to the sternum becomes inflamed and visibly swollen. It usually affects just one joint on one side, and the hallmark trio is tenderness, pain, and a noticeable knot of swelling right at the joint.2PubMed Central. What do we know about Tietze’s syndrome? The involved joints are typically in the upper ribs, so the swelling can sit very close to the center of the chest and feel alarming.
People often confuse Tietze’s syndrome with costochondritis, but the two are not identical. Costochondritis causes pain and tenderness in the same area but does not produce a visible or palpable lump. When there is actual swelling you can see or feel, Tietze’s is the more accurate label. Neither condition is dangerous. Pain and swelling tend to resolve on their own over weeks to months, and anti-inflammatory medication usually helps in the meantime. Case series going back decades have confirmed the benign nature of the syndrome.3Mayo Clinic Proceedings. Tietze’s Syndrome: Report of 13 Cases
Pectus Carinatum
Some people notice a more generalized prominence of the sternum rather than a discrete lump. If the breastbone itself pushes outward, creating a ridge or shelf in the center of the chest, the likely explanation is pectus carinatum, sometimes called “pigeon chest.” This is a congenital chest wall deformity where the cartilage between the ribs and the sternum grows excessively, pushing the bone forward. It usually becomes more obvious during the adolescent growth spurt, so a teenager or young adult may feel like a lump appeared out of nowhere when it was actually developing gradually.
Pectus carinatum rarely causes medical problems. In most cases the concern is cosmetic. Treatment options have evolved from open surgery to bracing, where a compressive orthotic device is worn over the chest to gradually reshape the cartilage. Awareness of the condition has grown as nonsurgical treatment options have become more widely available.4PubMed Central. Pectus carinatum: When less is more If the prominence is symmetrical and you have no pain, it is worth having a clinician confirm the diagnosis, but it is unlikely to need urgent intervention.
Lipomas and Other Soft-Tissue Growths
A lump that feels soft, moves slightly under the skin when pressed, and sits in the tissue above the bone rather than on it is often a lipoma, a benign collection of fat cells. Lipomas can appear almost anywhere on the body, and the chest wall is no exception. Most are small, painless, and grow slowly enough that you might not notice one for months or years. Case reports have documented chest wall lipomas with volume doubling times ranging from roughly 235 to 412 days, meaning it could take the better part of a year for one to double in size.5PubMed Central. Rapidly Growing Chest Wall Lipoma: Case Report and Calculating Volume Doubling Time
Epidermoid cysts (sometimes called sebaceous cysts, though that term is technically imprecise) are another common cause. These feel round and firm, sit just under the skin, and occasionally become inflamed or infected, at which point they turn red, tender, and warm. Neither lipomas nor epidermoid cysts are dangerous, but a doctor should evaluate any soft-tissue lump that grows quickly, feels hard or fixed, or causes persistent pain, because those features can point toward something less benign.
The Sternalis Muscle
Here is a cause most people never hear about: a small percentage of the population has an extra strip of muscle running vertically along one or both sides of the sternum, called the sternalis muscle. It is a normal anatomical variant, not a disease, but because it sits right on top of the breastbone it can feel like a firm lump under the skin, especially in lean individuals. The sternalis muscle has been documented during surgery, imaging, and routine mammography, where it can appear as an irregularly shaped density near the sternal edge of the image and raise concern for a mass.6PubMed. The sternalis muscle: an unusual normal finding seen on mammography
If the “lump” is symmetric, long rather than round, and feels like firm tissue rather than a discrete nodule, it could be this variant muscle. Cross-sectional imaging like CT or MRI readily distinguishes the sternalis from a tumor.7PubMed Central. The Sternalis Muscle—Incidental Finding of a Rare Chest Wall Muscle Variant During Keloid Excision-Chest Wall Reconstruction It does not need treatment and has no clinical significance beyond occasionally startling a radiologist.
Sternal Fracture Nonunion
If you have had a significant chest injury, even one that happened years ago, a bump on the sternum could be a nonunion, meaning the bone broke and never fully healed. The sternum can fracture from seatbelt impact, falls, or direct blows. While most sternal fractures heal without incident, some leave behind a palpable ridge or lump of callus where the bone attempted to repair itself. With the rise in surgical fixation of chest wall injuries worldwide, clinicians are seeing more patients present later with painful nonunions or prominent healed fracture sites.8Journal of Orthopaedic Trauma. Rib and Sternum Nonunions: Diagnosis and Treatment and Awareness of Other Potential Posttraumatic Pathology The lump in these cases is typically right over the fracture line and may be tender with deep breathing or pressing.
Infections of the Sternum
A sternal lump that is warm, red, and increasingly painful, especially if you also have a fever, could signal an infection of the bone itself. Primary sternal osteomyelitis, meaning a bone infection without prior surgery, is uncommon but well documented. It tends to present with chest pain, fever, chills, and a tender, swollen mass on the front of the chest.9PubMed Central. Primary Sternal Osteomyelitis caused by Staphylococcus aureus in an Immunocompetent Adult Even people with otherwise healthy immune systems can develop it. Case reports describe patients arriving at emergency departments after a couple of weeks of worsening chest pain and swelling, only to be diagnosed with a sternal infection.10PubMed Central. Primary sternal osteomyelitis: A case report
More commonly, sternal infections follow cardiac surgery that involves splitting the breastbone, but primary cases without prior surgery do occur. The key red flags are systemic illness (fever, feeling generally unwell) alongside local swelling. If the bump is hot and expanding and you feel sick, that combination warrants prompt medical attention rather than a wait-and-see approach.
Gout and the Sternum
Gout is best known for attacking the big toe, but it can flare in almost any joint, including the manubriosternal joint, the horizontal seam where the upper and middle portions of the sternum meet. When gout strikes there, it produces acute pain and visible swelling right in the center of the chest, which can be mistaken for a cardiac problem or a tumor. The diagnosis has been confirmed by joint aspiration showing urate crystals under polarized microscopy.11PubMed. Acute gout presenting in the manubriosternal joint If you have a history of gout or elevated uric acid levels and develop a sudden, very painful lump at the midchest, a gout flare deserves a place on the list of possibilities.
Primary Bone Tumors of the Sternum
Primary bone tumors that originate in the sternum are rare, making up only about half a percent of all primary bone tumors.12La Tunisie Médicale. Primary tumors of the sternum: about six cases When they do occur, they tend to present as a gradually enlarging, firm mass on the front of the chest. The most common malignant primary tumor of the sternum is chondrosarcoma, a cancer of cartilage. It often arises at the junction where the ribs attach to the sternum and presents as a painful, expanding mass.13PubMed Central. Chondrosarcoma of the Sternum: Surgical Challenges, Chest Wall Reconstruction, and Postoperative Management Other tumors documented in this location include osteosarcoma, plasmacytoma, and lymphoma.
Benign bone tumors can also occur. Osteomas and osteochondromas sometimes grow at the sternal surface or at the manubriosternal junction, creating a hard, bony lump that imaging may initially struggle to categorize. In one reported case, radiographic changes at the manubriosternal junction were initially read as a chronic inflammatory process before biopsy revealed a different picture entirely.14MOJ Clinical & Medical Case Reports. Surgical management of rare benign tumors of the sternum The rarity of these tumors is actually reassuring for most people. But a hard, painless mass that keeps growing is the classic profile that prompts imaging and often biopsy.
Metastatic Cancer and Lymph Node Swelling
Cancers that start elsewhere in the body occasionally spread to the sternum. The bone marrow inside the sternum has a rich blood supply, making it a potential landing site for circulating tumor cells. Sternal metastases have been documented from lung cancer, breast cancer, kidney cancer, and thyroid cancer, among others. These lesions can destroy bone from the inside and eventually produce a palpable mass that pushes through the outer surface. Metastatic deposits may appear as bone-destroying (lytic) or bone-forming (sclerotic) lesions on imaging.15PubMed Central. Sternal Metastasis of Lung Cancer: A Case Report and a Review of the Literature
In some cases the sternal mass is the very first sign that cancer exists. One case report described a woman who presented to her doctor with a small, hard lump in the middle of her sternum and no other symptoms. Workup eventually revealed metastatic breast cancer, despite a normal breast exam and no enlarged lymph nodes in the armpit.16PubMed Central. The Elusive Primary: Metastatic Adenocarcinoma of the Breast Presenting Solely as a Hard Sternal Mass Similarly, breast cancer can cause swelling along or beside the sternum when it spreads to the internal mammary lymph nodes, a chain of nodes running just behind the breastbone. This swelling can be the first clinically obvious sign of advanced disease.17PubMed. Sternal or parasternal involvement from breast cancer: a misleading clinical sign
These scenarios are uncommon, but they underline why a new, hard, painless, and growing sternal mass in an adult warrants imaging and possibly biopsy, especially in someone with a personal history of cancer.
Vascular Abnormalities
Very rarely, a pulsatile or expanding mass over the sternum can be vascular in origin. Large aneurysms of the ascending aorta sit directly behind the sternum, and in extreme cases an aneurysm can erode through the bone and present as a visible or palpable mass on the chest wall. One case report described a man in his seventies with a history of chest trauma who developed a saccular aortic aneurysm that protruded through the sternum and skin.18PubMed. Impending rupture of aortic aneurysm eroding skin and sternum: a rare condition This is an extraordinary finding and not something most people with a sternal bump need to worry about, but it is a reminder that any rapidly expanding, pulsating mass over the sternum is a medical emergency.
How Doctors Figure Out What the Lump Is
When you point out a sternal lump to a doctor, the first step is a physical exam. Location, texture, mobility, tenderness, and whether the lump seems to be in the skin, the soft tissue, or the bone itself all guide the next steps. Many lumps (xiphoid process, Tietze’s syndrome, lipomas) can be diagnosed clinically without any imaging at all.
When imaging is needed, a plain chest X-ray is usually the starting point. CT and MRI are the workhorses for evaluating chest wall masses in more detail, each with different strengths: CT excels at showing bone destruction and calcification, while MRI is better at characterizing soft-tissue involvement and the relationship of a mass to surrounding structures.19PubMed. Diagnostic and Imaging Approaches to Chest Wall Lesions In cases where cancer is suspected, PET/CT scanning can help assess whether a sternal lesion is metabolically active and whether disease exists elsewhere. Imaging also guides percutaneous biopsy when tissue sampling is needed to make a definitive diagnosis.20PubMed. Radiology of chest wall masses
When to Worry and When to Wait
With so many possible causes, the practical question is which lumps deserve a doctor’s visit and which can safely be monitored at home. A few features help sort them:
- Likely benign: The lump is at the very bottom of the sternum and feels like bone (probably the xiphoid). It is soft and movable under the skin (probably a lipoma or cyst). It appeared after a period of coughing, heavy lifting, or chest illness and is tender at a rib-sternum junction (probably Tietze’s syndrome).
- Worth getting checked soon: The lump is hard, fixed, and painless and has been growing over weeks. It appeared without any obvious cause. You have a personal history of cancer. You are losing weight, feeling unusually tired, or having night sweats.
- See a doctor promptly: The lump is warm, red, and accompanied by fever. It is pulsating. It appeared suddenly with severe pain. It is growing visibly over days rather than weeks.
Most people who notice a bump on their sternum for the first time are feeling their own anatomy or dealing with a minor inflammatory condition. The sternum is a bone you rarely poke at until something draws your attention there, and once you start pressing around, normal ridges and cartilage joints can feel surprisingly lumpy. Still, a lump that is new, growing, or accompanied by other symptoms deserves evaluation rather than reassurance from the internet alone.