What are the differential diagnoses for a diploic skull mass in an infant?

Differential Diagnosis of Diploic Space Mass in an Infant

The most common diploic space masses in infants are epidermoid/dermoid cysts and Langerhans cell histiocytosis, followed by vascular lesions including cavernous hemangiomas and intraosseous hemangiomas. 1

Primary Differential Diagnoses

Most Common Lesions

• Epidermoid/Dermoid Cysts: These represent the most frequently encountered skull lesions in the pediatric population, typically presenting as painless masses with slow growth 1

• Langerhans Cell Histiocytosis: The second most common diagnosis, often appearing as osteolytic lesions in the skull 1

Vascular Lesions

• Cavernous Hemangioma: Although rare in neonates, these can develop within the diploic space and should be considered in the differential diagnosis of suspected ossified cephalohematoma 2

  • These lesions can be present since birth and may be associated with prior hemorrhages 2
  • Ultrasound with color Doppler is essential to distinguish high-flow from low-flow vascular malformations 3

• Intraosseous Hemangioma: Another vascular lesion that occurs in the diploic space of pediatric patients 1

Fibro-Osseous Lesions

• Fibrous Dysplasia: Can present as early as 4 months of age with a hard, painless, progressively expanding mass 4
  • MRI shows an expansile lesion with dense calcification in the diploic space 4
  • Radiographs demonstrate irregular osteolytic lesions 4

Other Benign Lesions

• Infantile Myofibroma: A rare but documented cause of skull lesions in infants 1

• Osteoblastoma: Uncommon but possible in the pediatric skull 1

Clinical Presentation Patterns

• Most lesions present as painless masses (most common presentation) 1
• Median age at diagnosis is 9.5 years, though neonatal presentation is possible 1, 2
• Location: Most commonly affects occipital bone, followed by frontal, parietal, and temporal bones 1

Diagnostic Approach

Initial Imaging

• Ultrasound with color Doppler should be the first-line imaging modality to distinguish solid from cystic lesions and characterize vascularity without radiation exposure 3

• MRI with contrast provides superior soft tissue characterization and defines the relationship to adjacent structures, particularly for deep involvement or indeterminate findings 5, 3

• CT scan is reserved for evaluating bone involvement, calcification patterns, and osteolytic changes 4

Key Imaging Features to Assess

• T1-weighted MRI: Look for expansile lesions with calcification in the diploic space 4
• Radiographs: Identify osteolytic versus sclerotic patterns 4
• Vascular characteristics: Doppler assessment differentiates vascular from non-vascular masses 3

Important Clinical Pitfalls

• Do not assume all neonatal skull masses are cephalohematomas: Cavernous hemangiomas can mimic ossified cephalohematomas and require different management 2

• Intracranial extension is rare but must be excluded: Only 1 in 19 cases showed intracranial extension in a large pediatric series 1

• Malignancy is extremely rare in this age group and location, but tissue diagnosis through surgical excision is required when diagnosis remains uncertain after imaging 3, 1

• Recurrence after complete surgical resection is uncommon (only 2 of 19 cases in one series), making complete excision the definitive treatment 1

Management Principles

• Observation alone may be appropriate for small, asymptomatic lesions with characteristic benign imaging features 1

• Surgical excision is indicated for:

  • Persistent or enlarging masses 2
  • Lesions causing cosmetic deformity 4
  • Uncertain diagnosis requiring tissue confirmation 3, 1
  • Symptomatic lesions 4

• Complete surgical resection prevents recurrence and is curative for most benign lesions 1