What is the likely diagnosis and appropriate management for a firm, non‑mobile bony lump on the dorsal hand?

Bony Growth on Back of Hand: Diagnosis and Management

A firm, non-mobile bony lump on the dorsal hand is most likely an osteochondroma or Heberden's node (DIP joint osteophyte), and initial management should begin with plain radiographs to characterize the lesion and guide further workup.

Initial Diagnostic Approach

Start with plain radiographs of the hand to characterize the bony lesion, as this is the first-line imaging modality for suspected bone tumors 1. The radiographic appearance will determine all subsequent management decisions.

Key Radiographic Features to Assess

• Location specificity: Osteochondromas most commonly occur in the metaphyseal region of long bones and present as cartilage-capped bony outgrowths with cortical and medullary continuity with the parent bone 2, 3
• DIP joint involvement: If the lesion is at the distal interphalangeal joint, consider Heberden's nodes (osteophytes), which are bony prominences associated with osteoarthritis 4
• Benign vs. aggressive features: Assess for periosteal reaction, cortical destruction, or soft tissue mass that would suggest malignancy 1

Differential Diagnosis Based on Location

If Located on Bone Shaft (Osteochondroma Most Likely)

• Osteochondromas account for 30-35% of all benign bone tumors and are the most common benign bone tumor 5, 2
• These lesions appear as bony outgrowths with continuity of cortex and medullary canal with the parent bone 2, 3
• In the hand and phalanges, malignancy is extremely rare 1
• Most osteochondromas are asymptomatic and require no intervention unless causing mechanical symptoms 5

If Located at DIP Joint (Heberden's Node/Osteophyte)

• Heberden's nodes are clinical manifestations of DIP joint osteoarthritis with bony osteophyte formation 4
• Radiological DIP osteophytes are more specific than clinical Heberden's nodes for confirming osteoarthritis (poor agreement between clinical and radiological findings, K=0.36) 4
• High-resolution imaging shows these develop where soft tissue bulges through the capsule between dorsal tendons and collateral ligaments 6

When to Obtain Advanced Imaging

MRI Without Contrast Indications

Order MRI without contrast if radiographs show an indeterminate lesion or if symptoms are unexplained by radiographic findings 1:

• MRI improved grading of hand bone tumors compared to radiography alone, correctly upgrading malignant tumors in 8% and downgrading benign tumors in 12% of cases 1
• MRI provides superior soft tissue characterization and can assess for complications like bursa formation or neurovascular compromise 1
• For cartilaginous lesions specifically, MRI can help differentiate enchondroma from low-grade chondrosarcoma 1

CT Without Contrast Indications

• Reserve CT for cases where radiographs are negative but symptoms persist, or when evaluating complex osseous anatomy 1
• CT better defines cortical bone destruction and matrix mineralization than MRI 1
• Do not order CT with contrast for benign-appearing lesions, as it adds no diagnostic value 1

Management Algorithm

For Radiographically Benign Lesions

If the lesion appears definitively benign on radiographs (classic osteochondroma or DIP osteophyte):

• Asymptomatic osteochondromas require no intervention, only reassurance 5
• Symptomatic lesions causing pain, mechanical problems, or cosmetic concerns warrant surgical excision 5, 2
• Low-grade peripheral osteochondromas should be excised with a covering of normal tissue if surgery is indicated 1

For Indeterminate or Concerning Lesions

• Obtain MRI to further characterize tissue composition and anatomic extent 1
• Consider biopsy if malignancy cannot be excluded, though this is rarely needed for typical benign lesions 5
• Multidisciplinary evaluation before biopsy to determine optimal trajectory 1

Critical Red Flags Requiring Urgent Workup

Immediately escalate workup if any of these features are present:

• Pain at the site of a cartilaginous lesion may indicate malignant transformation 1
• Continued growth after skeletal maturity or cartilage cap >1.5 cm thick suggests malignancy 3
• Rapid size increase, new onset pain, or soft tissue mass 2, 3
• Malignant transformation occurs in 1% of solitary osteochondromas but is still extremely rare in hand lesions 1, 3

Common Pitfalls to Avoid

• Do not assume all dorsal hand lumps are ganglion cysts without imaging confirmation; ganglion cysts are soft and mobile, not bony and fixed 7
• Do not order MRI with contrast as first-line imaging for benign-appearing lesions, as it provides no additional diagnostic benefit 1
• Do not perform bone scan or PET/CT for definitively benign lesions on radiographs 1
• In the phalanges specifically, remember that malignancy is extremely rare, so avoid overaggressive workup 1