Movable Mass on Forehead: Evaluation and Management
Most Likely Diagnosis
A movable mass on the forehead is most commonly a benign lipoma, specifically a frontalis-associated lipoma located within or just beneath the frontalis muscle. 1, 2, 3
Key Clinical Features to Assess
- Mobility and consistency: Lipomas present as slowly growing, smooth masses with soft or firm consistency that are mobile beneath the skin 1, 3
- Age and gender: Mean age at presentation is 48 years, with male predominance 3
- Solitary presentation: 100% of forehead lipomas present as a single swelling 3
- Duration: These are slow-growing lesions, typically present for months to years 1, 3
- History of trauma: Blunt trauma has been postulated to contribute to formation, though etiology remains unknown 3
Critical Differential Diagnoses to Exclude
Benign Lesions
- Epidermal inclusion cyst: Most common misdiagnosis; these are typically more superficial than lipomas 2
- Pilar-type keratinous cyst: Can present as subcutaneous forehead mass 4
- Hematoma: Consider with recent trauma history 4
Malignant Lesions (Red Flags)
- Metastatic carcinoma or systemic malignancy: A significant number of subcutaneous scalp/forehead masses represent metastatic disease and may be the initial manifestation 4
- Plasmacytoma: Most frequent malignant diagnosis in one series (6/16 malignant cases) 4
- Melanoma, lymphoma, or other carcinomas: Can present as forehead masses 4
High-Risk Features Requiring Urgent Evaluation
If any of the following are present, consider malignancy and proceed with imaging before surgical intervention:
- Firm or fixed consistency (not mobile) 5
- Rapid growth (present <2 weeks or rapidly enlarging) 5
- Size >1.5 cm 5
- Non-tender mass 5
- Age >40 years with new mass 5
- Ulceration of overlying skin 5
- History of malignancy 4
Recommended Diagnostic Approach
For Low-Risk, Mobile, Soft Masses (Presumed Lipoma)
Surgical excision under local anesthesia is both diagnostic and therapeutic, with no preoperative imaging required. 3
- Surgical technique: Transverse forehead-crease incision is most commonly adopted 3
- Critical anatomical consideration: Exploration beneath the frontalis muscle is often required for complete excision, as these lipomas are typically located within or just below this muscle 2, 3
- Alternative approach: Endoscopic removal via small scalp incision behind hairline for superior cosmesis, though this has limitations for large masses 6
For High-Risk Features or Diagnostic Uncertainty
Obtain imaging before surgical intervention to exclude intracranial extension or malignancy:
- MRI orbits, face, and neck without and with IV contrast: Best characterizes soft-tissue components and can distinguish benign from malignant features 7
- CT maxillofacial with IV contrast: Alternative if MRI unavailable; useful for evaluating osseous involvement 7
- Fine-needle aspiration (FNA): Provides rapid diagnosis for suspected malignancy and can guide appropriate therapy 4
Common Pitfalls to Avoid
- Assuming all forehead masses are benign cysts: Malignancy can present as subcutaneous forehead masses and may be the initial manifestation of systemic disease 4
- Inadequate depth of dissection: Forehead lipomas are often misdiagnosed as superficial cysts, but the correct anatomical plane is beneath the frontalis muscle 2, 3
- Performing open biopsy before imaging in high-risk patients: This can seed tumor cells and worsen outcomes if malignancy is present 5
- Incomplete removal: Ensure complete excision to prevent recurrence; endoscopic approach has higher risk of incomplete removal 6
Expected Outcomes
- Recurrence: No evidence of recurrence after complete excision of benign lipomas 1
- Cosmetic results: Excellent with proper surgical technique, especially with endoscopic approach or forehead-crease incision 3, 6
- Complications: Hematoma and swelling are most common; apply compressive dressing for 2 days postoperatively 6