The area under your right breast sits over a layered stack of tissue that includes skin, fat, breast glandular tissue, fascia, chest wall muscles, ribs, and cartilage, with the liver and gallbladder tucked just below on the right side. Pain or a lump in this region can come from any of those layers, which is why the list of possible causes ranges from a strained intercostal muscle to a gallbladder flare to a benign breast cyst. Most causes turn out to be non-cancerous and treatable, but the sheer variety of structures crowded into this space means the same symptom can point in very different directions depending on the details.
What Actually Sits Under the Breast
The breast itself rests on the chest wall like a soft cushion draped over a frame. That frame is the pectoralis major muscle, the ribs, and the intercostal muscles that fill the gaps between them. The lower edge of the breast, called the inframammary fold, is anchored to the chest wall by layers of fascia. Anatomical studies place this fold roughly at the level of the fifth or sixth rib, though the exact position varies by individual. One dissection study found the fold is created by a multilayered fascial structure anchored mainly at the fourth and fifth ribs, with the skin effectively hanging from those attachment points rather than being stuck directly to a single rib.
Beneath the bony chest wall on the right side, things get organ-dense quickly. The lower lobe of the right lung and its surrounding pleural lining sit behind the upper ribs. The dome of the liver, the body’s largest internal organ, rises up under the right lower ribs and can extend as high as the fifth intercostal space. The gallbladder tucks in just beneath the liver’s edge. So when you press into the area under your right breast, you are pushing through skin, fat, breast tissue, muscle, bone, and potentially compressing structures that connect to your digestive or respiratory systems. That layered anatomy is exactly why pain “under the right breast” can mean so many different things.
Musculoskeletal Causes
The most common reason for pain under either breast is something going on with the chest wall itself. Costochondritis, an inflammation of the cartilage connecting the ribs to the breastbone, causes a sharp or aching pain that gets worse when you press on the affected area, take a deep breath, or twist your torso. It often affects the cartilage at the second through sixth ribs and can feel alarming because the pain seems to come from inside the chest. There is usually no swelling or lump, and the pain tends to resolve on its own or with anti-inflammatory medication over a few weeks.
A less well-known musculoskeletal culprit is slipping rib syndrome, which happens when one of the lower ribs (typically the eighth through tenth) becomes abnormally mobile and slips under the rib above it, irritating the intercostal nerve in between. This produces a clicking or popping sensation along the lower rib margin, sometimes with intense, stabbing pain that radiates into the upper abdomen or back. Because these lower ribs sit right at or just below the breast, the pain can feel like it originates in the breast itself. Slipping rib syndrome is poorly understood and often goes undiagnosed for years; a physical exam using a “hooking maneuver,” where a clinician curls their fingers under the rib margin and pulls outward, can reproduce the click and the pain, helping confirm the diagnosis.1PubMed Central. A Comprehensive Review of Slipping Rib Syndrome: Treatment and Management Dynamic ultrasound can also be useful, though the definitive proof is typically pain relief after a nerve block or surgical correction.2PubMed Central. A Review of Slipping Rib Syndrome: Diagnostic and Treatment Updates to a Rare and Challenging Problem
Muscle strains in the pectoralis or the intercostal muscles can also produce localized tenderness under the breast. These are especially common after heavy lifting, a new exercise routine, or repetitive overhead movements. The pain is usually reproducible with certain motions and improves with rest.
Gallbladder and Upper Abdominal Sources
Because the gallbladder sits directly under the right lower ribs, gallbladder pain is one of the most frequent non-breast explanations for discomfort under the right breast. A gallstone attack produces a visceral, cramping pain typically felt in the upper right abdomen or the pit of the stomach, and it often radiates to the back and right shoulder blade.3PubMed Central. ABC of the upper gastrointestinal tract. Upper abdominal pain: Gall bladder The pain can last anywhere from twenty minutes to several hours, frequently starts after a fatty meal, and may be accompanied by nausea. Because the gallbladder sits so high, many people describe this pain as being “under the breast” or “in the ribs” rather than in the belly. If the pain comes with fever or persistent tenderness, it may signal cholecystitis, an infection of the gallbladder that requires prompt medical attention.
Liver-related issues, including hepatitis or liver congestion from heart failure, can also produce a dull ache or sense of fullness in the right upper quadrant that people localize to the underside of the right breast. These conditions are less sudden than a gallstone attack and tend to come with other clues like fatigue, jaundice, or leg swelling.
Mondor’s Disease and Vascular Causes
If you feel a firm, rope-like cord running along the skin under or on the side of your breast, especially one that appeared suddenly and is tender to touch, the cause may be Mondor’s disease. This is a thrombophlebitis of a superficial vein in the breast or chest wall, meaning a blood clot forms in one of the small veins just under the skin. The cord is often most obvious when you lift the arm on the same side or raise the breast, and it can sometimes pull the overlying skin inward, creating a dimple or groove that looks worrying.4PubMed Central. Superficial Thrombophlebitis of the Breast (Mondor’s Disease): An Uncommon Localization of Common Disease
In the early phase the cord is sore and the skin around it may be red. Over the following weeks the clot organizes and the vein recanalizes, turning the cord into a painless fibrous band that eventually resolves on its own.5PubMed Central. Postbiopsy Mondor Disease as an Early Indicator of Elevated Thrombophlebitis Risk: A Case Report On ultrasound, the hallmark is a superficial vessel with no blood flow on Doppler imaging, sometimes with a visible clot inside. On mammography, it shows up as a tubular density.6PubMed. Mondor’s disease of the breast: sonographic and mammographic findings Mondor’s disease is benign and usually self-limiting, but clinicians take it seriously because the skin retraction and palpable finding can mimic breast cancer on a physical exam. One systematic review found that roughly 15% of Mondor’s cases were associated with an underlying breast cancer, making imaging follow-up important even though the cord itself is harmless.4PubMed Central. Superficial Thrombophlebitis of the Breast (Mondor’s Disease): An Uncommon Localization of Common Disease
Benign Breast Lumps
The breast tissue that extends under and around the lower breast can develop several kinds of benign lumps. The most common in younger women is a fibroadenoma, a firm, smooth, rubbery lump that moves easily when you push on it. Fibroadenomas are noncancerous growths of breast glandular and connective tissue and typically show up as painless lumps found during self-exam or routine imaging. Diagnosis usually relies on a combination of clinical examination, breast imaging, and pathological confirmation if needed.7PubMed Central. Understanding Fibroadenoma of the Breast: A Comprehensive Review of Pre-operative and Post-operative Clinicopathological Correlations Many fibroadenomas are monitored rather than removed, especially if they are small and not growing.
Breast cysts are another frequent finding. These fluid-filled sacs often fluctuate with the menstrual cycle, becoming larger and more tender before a period and shrinking afterward. Simple cysts are almost always benign and can be confirmed with ultrasound. Complex cysts with irregular walls or internal debris occasionally need aspiration or biopsy to rule out something more concerning.
Fat necrosis is a less familiar benign condition in which fatty tissue in the breast breaks down, usually after trauma or surgery. The damaged fat undergoes a chemical process called saponification, and the result can be a firm, irregular lump that looks worryingly like cancer on imaging.8American Journal of Case Reports. Atraumatic Breast Fat Necrosis Mimicking Malignancy in End-Stage Renal Disease: A Case Report The key differentiator is usually a biopsy, though in some cases the combination of imaging findings and a clear history of injury to the area can be enough for a confident diagnosis.
Epidermoid cysts, the same type of cyst that forms elsewhere on the body when skin cells get trapped under the surface, can occasionally show up in the breast. These are extremely rare in breast tissue and can become complicated by infection or rupture.9PubMed Central. Breast epidermoid cyst: a case report They are benign, but because any unusual breast mass warrants investigation, they are typically removed and sent for pathology.
Shingles and Nerve-Related Breast Pain
One of the more surprising causes of pain under the right breast is shingles (herpes zoster). The varicella-zoster virus, the same virus that causes chickenpox, stays dormant in nerve roots along the spine and can reactivate years or decades later. When it reactivates in one of the thoracic nerve roots that supply the chest wall, the result is a band of burning or stabbing pain that wraps around one side of the body, often following the curve of a rib. Early on, the pain can precede the characteristic blistering rash by several days, during which time it is easily mistaken for a heart, lung, or breast problem.10PubMed Central. A Rare Clinical Entity in the Differential Diagnosis of Mastalgia: Thoracic Zona
Thoracic shingles involving the T4 through T6 dermatomes can produce pain that feels like it is coming from directly under or within the breast. Once the vesicular rash appears, usually in a stripe on one side of the body, the diagnosis becomes clear. Antiviral medication works best when started within 72 hours of the rash appearing, so recognizing early breast-area pain as a possible nerve-related cause matters for timely treatment.
Breast Infections and Abscesses
A breast abscess is a localized collection of pus inside the breast tissue that causes pain, swelling, redness, and warmth. It is most common during breastfeeding, when bacteria enter through a cracked nipple, but non-lactational breast abscesses also occur. One documented case involved a non-lactating 33-year-old woman who developed a painful, growing mass in the right breast over three years, accompanied by intermittent fever and general weakness.11Journal of Ayurveda and Integrated Medical Sciences. A Case Report on Ayurvedic management of Stana Vidradhi (Non-Lactational Breast Abscess) Non-lactational abscesses can be associated with smoking, diabetes, or nipple piercings. Treatment usually involves antibiotics and drainage, either with a needle or a small surgical incision.
Ectopic Breast Tissue
Some people have extra breast tissue that developed along the embryonic “milk line,” a ridge that runs from the armpit to the groin. This ectopic tissue can appear anywhere along that line, including below the normal breast boundary or in the armpit. It often goes unnoticed until hormonal changes, especially pregnancy and breastfeeding, cause it to swell and become painful. Ectopic breast tissue can undergo the same pathological changes as normal breast tissue, including fibrocystic changes, fibroadenomas, and mastitis, and in adolescents it has been linked to cyclic pain tied to menstruation.12PubMed Central. Ectopic breast tissue with milky secretions on the axillae in a lactating Filipino female: A case report If the tissue causes persistent symptoms, surgical excision is an option, and recurrence after removal is uncommon.
Lung and Pleural Causes
Because the lower lobe of the right lung and the pleural membrane that wraps it sit just behind the ribs under the breast, conditions affecting these structures can produce pain in the same area. Pleurisy, an inflammation of the pleural lining, causes a sharp pain that worsens with breathing or coughing. A pleural effusion, which is fluid collecting in the pleural space, can produce a heavy, pressure-like sensation under the breast that may be accompanied by shortness of breath. One case report described a patient who presented with right-sided pleuritic chest pain and fever that was initially treated as bacterial pleurisy, only for the underlying cause to be a spinal infection producing referred pain.13Cureus. Pleuritic Chest Pain as an Initial Presentation of Pyogenic Spondylitis The takeaway is that pain felt under the breast does not always originate in the structures directly under the breast; referred pain from the spine, diaphragm, or pleura can masquerade as a local problem.
When a Lump Under the Breast Could Be Cancer
The lower portion of the breast is a less common site for breast cancer compared to the upper outer quadrant, where about half of all breast cancers arise. But tumors do develop in the lower quadrants, and there is evidence they may carry a worse prognosis. A study of over 1,500 women with early-stage breast cancer found that tumors in the lower-inner quadrant carried roughly twice the risk of breast cancer death compared to tumors in the upper-outer quadrant, after adjusting for other variables. That increased risk was particularly pronounced for tumors larger than 10 millimeters.14PubMed. Tumor location of the lower-inner quadrant is associated with an impaired survival for women with early-stage breast cancer One theory is that lower-inner tumors are more likely to drain into internal mammary lymph nodes, which are harder to evaluate and treat than the axillary nodes typically sampled during surgery.
This does not mean every lump under the breast is cancer. The vast majority of breast lumps are benign. But it does mean that a new, persistent lump in the lower breast deserves the same workup as one anywhere else, and possibly extra attention because of the drainage pattern.
How Doctors Evaluate Under-Breast Pain and Lumps
If you go to a clinician with a complaint of pain or a lump under the right breast, the evaluation typically starts with a detailed history: when the pain started, whether it changes with your cycle or with breathing, whether you have had any trauma, surgery, or recent illness. A physical exam will involve pressing on the chest wall, the rib cartilage, and the breast tissue to see whether the tenderness is superficial (suggesting a musculoskeletal or skin cause) or deep (pointing toward organs beneath the ribs).
Imaging is the next step when the cause is not obvious. Ultrasound and mammography are both highly sensitive for picking up breast cancer in patients with focal breast pain. One study evaluating patients who had breast pain without a palpable lump found that both mammography alone and ultrasound alone had 100% sensitivity for detecting cancer in that group, though both also flagged many non-cancerous findings.15PubMed. Role of breast ultrasound and mammography in evaluating patients presenting with focal breast pain in the absence of a palpable lump For suspected gallbladder or liver pathology, an abdominal ultrasound is standard. For possible pleural issues, a chest X-ray or CT scan provides answers. The choice of imaging depends largely on where the clinician thinks the problem is coming from after the exam, which is why describing your symptoms precisely, especially whether pain is affected by breathing, eating, or movement, helps direct the workup.
Rib Anatomy and the Inframammary Fold
One reason the under-breast area is so prone to confusing symptoms is that the inframammary fold itself is a complex anatomical boundary. Rather than being a simple crease, the fold is formed by a multilayered fascial structure that repeatedly fuses and separates as it connects the skin to the deep fascia of the pectoralis muscle, mainly around the fourth and fifth ribs.16PubMed. The fascial structure of the breast: New findings on the anatomy of the inframammary fold Imaging studies using CT and MRI have confirmed that the fold position correlates closely with specific rib levels, though different methods have placed it at the fifth intercostal space or the sixth rib depending on the technique used.17PubMed Central. The inframammary fold: Structure, clinical considerations, and reconstructive techniques This matters because the fold is the dividing line between what your brain registers as “breast” pain and “rib” or “abdominal” pain, and that dividing line sits differently on different people. A condition involving the fifth rib could feel like it is under the breast on one person and in the breast on another.
Moisture and friction in the fold also create their own set of issues. Intertrigo, a fungal or bacterial skin infection that thrives in warm, moist skin folds, is extremely common under the breasts and produces redness, itching, and sometimes a raw, weeping rash. It is not a lump and is usually not dangerous, but it can be persistent and uncomfortable without treatment. Keeping the fold dry and applying antifungal cream typically clears it up.
Right Side Versus Left Side
People often wonder whether pain under the right breast is more or less worrying than pain under the left. The answer depends on the suspected cause. The gallbladder and most of the liver sit on the right, so gallstone pain and hepatic causes are overwhelmingly right-sided. The heart sits slightly to the left, so cardiac-related chest pain is more often left-sided, though it can present on the right in atypical cases. Musculoskeletal causes, breast lumps, Mondor’s disease, shingles, and pleural problems can occur on either side with roughly equal frequency. The right-sided location does narrow the differential somewhat by making gallbladder disease a more prominent suspect and heart disease a slightly less likely one, but it does not eliminate any category entirely. Any new, unexplained lump or severe pain under either breast warrants evaluation, regardless of side.