Xiphoid Osteochondroma

Overview

Osteochondroma is a benign bone tumor that arises from the growth plate (physis) and is covered by a cartilage cap. While most osteochondromas occur in the long bones of the arms and legs, a xiphoid osteochondroma develops on the xiphoid process – the small, lowest portion of the sternum.

Key points:

• Who it affects: Primarily adolescents and young adults (10–30 years) because the tumor originates from the growth plate, which is still active during skeletal maturation.
• Prevalence: Osteochondromas are the most common benign bone tumor, representing 30–50 % of all benign bone lesions ^[1]. Xiphoid involvement is rare, accounting for less than 1 % of all osteochondromas ^[2].
• Gender: Slight male predominance (about 1.5 : 1) for overall osteochondromas; limited data suggest a similar pattern for sternal lesions.

Symptoms

Many osteochondromas are discovered incidentally because they cause no discomfort. When symptoms occur, they are usually related to the mass effect on surrounding structures.

Typical symptom list

• Painless lump: A firm, immobile nodule palpable at the lower sternum.
• Localized pain: Tenderness that worsens with pressure, deep breathing, or certain arm movements.
• Chest wall discomfort: A dull ache that may be mistaken for costochondritis.
• Radiating pain: In rare cases, irritation of intercostal nerves can cause pain that radiates to the upper abdomen or back.
• Skin changes: Overlying skin may become thin, reddened, or ulcerated if the lesion fractures.
• Motion limitation: If the osteochondroma interferes with the range of motion of the shoulders or trunk.
• Respiratory symptoms: Very large lesions can press on the diaphragm or pleura, causing shortness of breath or a feeling of “tightness” in the chest.
• Neurological signs: Numbness or tingling in the medial arm or upper abdomen if a nerve is compressed (extremely uncommon).
• Growth: Sudden increase in size after skeletal maturity may signal malignant transformation (see Complications).

Causes and Risk Factors

The exact cause of solitary osteochondroma is not fully understood, but several mechanisms have been identified.

Genetic factors

• Hereditary Multiple Exostoses (HME): An autosomal‑dominant condition caused by mutations in the EXT1, EXT2, or EXT3 genes. Patients develop dozens of osteochondromas, sometimes including the xiphoid process.

Developmental factors

• Aberrant enchondral ossification during growth plate maturation leads to a cartilaginous outgrowth that ossifies.
• Trauma or micro‑fractures of the growth plate may act as a trigger, though this link is weak.

Risk factors for a xiphoid osteochondroma

• Age: Growth plates close around age 20‑25, so most lesions appear earlier.
• Male sex: Slightly higher incidence.
• Family history of HME: Increases the odds of solitary lesions as well.
• Prior chest wall trauma: May predispose to localized growth plate disturbances.

Diagnosis

Because a xiphoid osteochondroma is uncommon, a systematic approach is essential to differentiate it from other chest wall masses.

Clinical evaluation

• History: onset, growth pattern, pain characteristics, prior trauma, family history of HME.
• Physical exam: palpation of a hard, non‑fluctuant, immobile mass at the inferior sternum.

Imaging studies

• Plain radiography (X‑ray): First‑line. Shows a bony protrusion continuous with the cortex and medullary cavity of the xiphoid process, often with a thin cortical “shell.”
• Computed Tomography (CT): Provides 3‑dimensional detail, delineates the cartilage cap thickness, and assesses proximity to vital structures (heart, lungs, diaphragm).
• Magnetic Resonance Imaging (MRI): Best for evaluating the cartilage cap; a thickness > 2 cm in adults raises concern for malignant transformation.
• Ultrasound: Useful in children for a quick, radiation‑free assessment of superficial lesions.

Laboratory tests

Routine blood work is usually normal. If malignancy is suspected, serum alkaline phosphatase may be modestly elevated, but imaging remains the primary diagnostic tool.

Biopsy

Rarely required because imaging characteristics are distinctive. If the cartilage cap is unusually thick or the lesion shows aggressive features, a core needle biopsy under CT guidance may be performed to exclude chondrosarcoma.

Treatment Options

Management depends on symptom severity, lesion size, and risk of complications.

Observation (Watchful waiting)

• Indicated for asymptomatic, small (< 3 cm) lesions with a cartilage cap ≤ 1 cm.
• Follow‑up schedule: clinical exam and X‑ray every 12 months until skeletal maturity, then every 2–3 years.
• Advantages: avoids surgical risks.

Surgical excision

Recommended when the lesion is painful, enlarging, or causing functional impairment.

• Procedure: Midline or paramedian incision over the xiphoid process, careful subperiosteal dissection, removal of the osteochondroma with a margin of normal bone, and reconstruction of the chest wall if needed.
• Minimally invasive options: Endoscopic or video‑assisted thoracoscopic approaches have been reported for selected cases, reducing scar length and postoperative pain.
• Complications of surgery: Infection, hematoma, chest wall instability, injury to the diaphragm or internal mammary vessels.

Medications

• Analgesics (acetaminophen or NSAIDs) for pain control.
• Muscle relaxants if associated muscle spasm occurs.
• There is no pharmacologic therapy to shrink the tumor itself.

Post‑operative care

• Restrict heavy lifting and strenuous upper‑body activity for 4–6 weeks.
• Gentle range‑of‑motion exercises for the shoulders to prevent stiffness.
• Scar management: silicone gel or sheets once the wound is healed.
• Regular follow‑up imaging at 6 months and then annually for 2 years.

Living with Xiphoid Osteochondroma

Daily management tips

• Monitor size: Feel the area monthly; note any rapid growth.
• Protect the area: Avoid direct blows to the sternum (e.g., in contact sports). Use protective padding if participation is unavoidable.
• Pain control: Use OTC NSAIDs as needed, but follow dosing guidelines to protect the stomach and kidneys.
• Posture: Maintain good thoracic posture to reduce pressure on the xiphoid region.
• Exercise: Low‑impact activities (walking, swimming, stationary cycling) are safe. Gradually re‑introduce upper‑body strength work after surgeon clearance.
• Weight management: Excess body weight can increase mechanical stress on the chest wall.
• Regular check‑ups: Keep scheduled appointments; bring any new symptoms to your clinician’s attention.

Psychosocial considerations

Although benign, visible chest wall masses can cause self‑consciousness. Counseling or support groups for patients with benign bone tumors can be helpful.

Prevention

Because most osteochondromas arise from developmental cartilage growth, primary prevention is limited.

• Genetic counseling: Families with known HME should seek counseling to understand inheritance patterns.
• Injury avoidance: Use protective gear during high‑impact sports to reduce chest wall trauma that could theoretically provoke abnormal growth.
• Healthy nutrition: Adequate calcium and vitamin D support normal bone development, though they do not prevent osteochondroma formation.

Complications

While most xiphoid osteochondromas remain harmless, several complications merit attention.

• Fracture of the osteochondroma: Can cause sharp pain and skin ulceration.
• Compression of adjacent structures: Large lesions may press on the diaphragm, causing dyspnea, or on intercostal vessels, leading to bleeding.
• Malignant transformation: Rare (< 1 % of solitary osteochondromas) but possible progression to chondrosarcoma. Warning signs include rapid growth after age 30, pain at rest, and cartilage cap > 2 cm on MRI ^[3].
• Cosmetic deformity: Prominent chest wall bump.
• Infection: Post‑operative wound infection if surgery is performed.

When to Seek Emergency Care

References

1. Mayo Clinic. Osteochondroma. Updated 2023. https://www.mayoclinic.org/diseases-conditions/osteochondroma.
2. World Health Organization. Benign bone tumours: epidemiology and classification. WHO Press, 2022.
3. National Cancer Institute. Chondrosarcoma Treatment (PDQ®)–Patient Version. 2024. https://www.cancer.gov/types/bone/patient/chondrosarcoma-treatment-pdq.
4. Cleveland Clinic. Hereditary Multiple Exostoses (HME). 2023. https://my.clevelandclinic.org/health/diseases/16776-hereditary-multiple-exostoses.
5. American College of Radiology. ACR–SAR–SPR Practice Parameter for Imaging of Benign Bone Tumors. 2021.