What is the differential diagnosis for a lump on the chest?

Differential Diagnosis for a Chest Wall Lump

A palpable chest wall lump has a broad differential diagnosis ranging from benign soft tissue masses to primary malignancies and metastatic disease, requiring systematic evaluation based on location, patient demographics, and imaging characteristics to guide appropriate management. 1

Primary Diagnostic Categories

The differential diagnosis can be organized into eight main categories:

Benign Etiologies

• Lipomas and soft tissue masses - most common presentation in primary care settings 2
• Nerve sheath tumors - can present as palpable axillary or chest wall masses 1
• Vascular lesions - including hemangiomas and arteriovenous malformations 1
• Infectious/inflammatory processes - including abscesses and inflammatory lymphadenopathy 1
• Autoimmune disease manifestations 1
• Benign bone and cartilage tumors - arising from ribs or sternum 3
• Hamartomas - characterized by intranodular fat and popcorn calcification on imaging 1, 4

Malignant Etiologies

Malignant chest wall tumors are classified into eight diagnostic categories: muscular, vascular, fibrous and fibrohistiocytic, peripheral nerve, osseous and cartilaginous, adipose, hematologic, and cutaneous origins 5. Additional malignancies include:

• Primary breast malignancy - particularly in women with axillary presentation 1
• Primary lung cancer invading chest wall - occurs in approximately 5% of lung cancers 2
• Sarcomas - including pleomorphic liposarcoma, osteogenic sarcoma, giant cell tumors, Ewing sarcoma, and synovial sarcoma 6, 7, 5
• Metastatic disease from non-breast malignancies 1
• Lymphoma 1

Risk Stratification by Patient Demographics

Women with Axillary Lumps

• Risk of malignancy is low (7%) in women without personal history of breast cancer, but increases with age 1
• Primary breast cancer presenting as isolated axillary adenopathy occurs in less than 1% of cases 1

Age-Related Risk

• Malignancy risk increases with an odds ratio of 1.04-2.2 for every 10-year increase in age 4

Critical Imaging Features

Features Suggesting Malignancy

• Spiculated or irregular margins - increase malignancy likelihood more than 5-fold (LR 5.5) 4, 8
• Size greater than 8 mm - approximately 1.1-fold increased odds per 1 mm diameter increase 4, 8
• Pleural retraction - increases likelihood 1.9-fold 4, 8
• Vascular sign (vessels leading into mass) - increases likelihood 1.7-fold 4, 8
• Rapid growth - volume doubling time less than 400 days 4
• Cortical bone destruction - detected on CT imaging 5
• Hypervascular soft tissue mass on ultrasound with rib erosion - highly suspicious for malignancy 2

Features Suggesting Benignity

• Diffuse, central, laminated, or "popcorn" calcification - odds ratio 0.07-0.20 for malignancy 1, 4, 8
• Smooth or polygonal margins - make malignancy 5 times less likely (LR 0.2) 4, 8
• Intranodular fat with popcorn calcification - pathognomonic for hamartoma 1, 4, 8
• Stability for at least 2 years - characteristic of benign nodules 4

Recommended Diagnostic Algorithm

Initial Evaluation

1. Obtain thorough history assessing duration, associated symptoms (pain, voice changes, dysphagia, weight loss, fever, hemoptysis), smoking history, personal/family cancer history, and risk factors 4, 9

2. Physical examination should include visualization of deeper structures if malignancy risk is elevated 9

Imaging Approach

For superficial chest wall masses:

• Ultrasound is the first-line imaging modality 9, 2
• Provides excellent detail for superficial structures and can identify hypervascularity, tissue characteristics, and bone involvement 9, 2

For axillary lumps in women:

• Diagnostic mammogram/digital breast tomosynthesis plus axillary ultrasound to evaluate for underlying breast lesions 1
• DBT increases primary breast cancer detection rate, particularly in women ages 40-49 years 1

For suspected chest wall invasion or deeper involvement:

• CT chest to determine bony involvement, chest wall invasion, or pleural space involvement 1
• More sensitive than radiography for detecting cortical destruction and calcified tumor matrix 5
• MRI allows more accurate delineation of tumor extent and invasion 5

Tissue Diagnosis

• Image-guided core biopsy is preferred over fine-needle aspiration when diagnosis remains uncertain 9
• US-guided biopsy can be performed for accessible axillary or chest wall masses 1, 2

Critical Pitfalls to Avoid

• Do not assume all enlarging superficial masses are benign lipomas - prompt investigation is essential as primary lung tumors can present as superficial chest wall masses 2
• Physical examination alone is insufficient - correctly identifies only 85% of soft tissue masses 9
• Do not use FDG-PET/CT as initial imaging for axillary masses of unknown etiology due to low yield without first confirming malignant etiology 1
• Malignant chest wall tumors typically manifest as painful, rapidly growing, large palpable masses - these features warrant urgent evaluation 5
• If benign calcification patterns are not clearly evident on initial imaging, further evaluation is mandatory 1