What could be the cause of an acute enlarged soft lump above the lateral edge of the eyebrow in an adult male?

Acute Enlarged Soft Lump Above Lateral Eyebrow in Adult Male

The most likely diagnosis is a dermoid cyst, epidermoid (inclusion) cyst, or lipoma, but given the acute presentation with enlargement, urgent ultrasound imaging within 2 weeks is mandatory to exclude soft tissue sarcoma, as any unexplained lump that is increasing in size requires immediate imaging evaluation. 1, 2

Immediate Diagnostic Approach

Obtain urgent ultrasound within 2 weeks, as this is the single most important first-line diagnostic tool for triaging soft tissue masses suspicious for malignancy. 1 The acute enlargement is a critical red flag—increasing size is the single most important warning sign for soft tissue sarcoma and warrants urgent investigation. 1

Key Clinical Features to Assess

• Size measurement: Masses >5 cm have significantly higher malignancy risk and require direct specialist referral. 1
• Depth assessment: Determine if the mass is superficial (above fascia) or deep (beneath fascia), as deep location is highly concerning for sarcoma. 1
• Pain characteristics: The presence of pain, especially night pain, is a red flag requiring investigation. 1
• Growth rate: Document the timeline of enlargement—rapid growth over days to weeks versus months. 1
• Mobility: Assess whether the mass is mobile or fixed to underlying structures. 3

Differential Diagnosis by Likelihood

Most Common Benign Lesions (Superficial Location)

• Dermoid cyst: Most common soft tissue lesion of the eyebrow region, typically present for months without substantial size change, located in deep periosteal plane. 4, 2
• Epidermoid (inclusion) cyst: Part of standard differential for eyebrow masses. 2
• Lipoma: Common subcutaneous lesion, though acute enlargement is atypical. 2
• Pilomatrixoma: Common eyebrow region lesion. 4

Uncommon but Important Diagnoses

• Pleomorphic adenoma: Rare in eyebrow region (typically salivary/lacrimal gland origin), presents as prominent soft tissue lesion in deep periosteal plane. 4
• Sebaceous carcinoma: Unilateral intense bulbar conjunctival infection, may appear as hard nodular mass with yellowish discoloration, often misdiagnosed as chalazion. 3

Malignant Considerations (Critical to Exclude)

Soft tissue sarcoma must be excluded when any of these red flags are present: 1

• Increasing size (present in this case)
• Size >5 cm
• Deep location
• Pain

Imaging Algorithm

First-Line: Ultrasound

Characteristic ultrasound features by diagnosis: 5

Benign lipoma:

• Well-circumscribed, hyperechoic or isoechoic compared to surrounding fat
• Thin, curved echogenic lines within encapsulated mass
• Minimal to no internal vascularity on Doppler
• No acoustic shadowing 5

Concerning features requiring advanced imaging or biopsy: 5

• Atypical ultrasound features
• Size >5 cm
• Deep-seated location
• Rapid growth
• Pain or tenderness

Second-Line: MRI

Obtain MRI if: 6, 5

• Ultrasound shows atypical features
• Deep-seated mass
• Mass >5 cm
• Rapid growth documented
• Diagnostic uncertainty on ultrasound

MRI provides the most accurate information for diagnosis and surgical planning for soft tissue tumors. 6

Staging if Malignancy Suspected

If ultrasound or MRI findings suggest sarcoma: 6

• CT chest to exclude pulmonary metastases (predominant metastatic pattern)
• Regional lymph node assessment by ultrasound or cross-sectional imaging

Referral Pathways

Urgent Specialist Referral (Within 2 Weeks)

Refer via suspected cancer pathway if: 1, 6

• Ultrasound findings suggestive of soft tissue sarcoma
• Uncertain ultrasound findings with persistent clinical concern
• Multiple red flag features present (increasing size, >5 cm, deep location, pain)

All suspected soft tissue sarcomas must be managed by a specialist Sarcoma MDT. 6

Routine Referral

For typical benign features on ultrasound in small (<5 cm), superficial, asymptomatic lesions, observation with clinical follow-up is sufficient. 5

Critical Pitfalls to Avoid

• Never assume all superficial masses are benign: Atypical lipomatous tumors can mimic benign lipomas but require different surgical management with MDM-2 amplification testing. 1, 5
• Do not rely on "normal" appearance alone: A painless mass can be deceptive—the most common presentation of sarcoma is a painless enlarging soft tissue mass. 1
• Avoid biopsy before imaging: Complete imaging assessment should precede any biopsy to allow proper surgical planning. 6
• Do not dismiss recent trauma history: History of recent injury does not exclude sarcoma. 1

Tissue Diagnosis When Indicated

If malignancy suspected after imaging: 6

• Percutaneous core needle biopsy is the standard approach
• Multiple cores should be obtained under image guidance
• Biopsy tract must be planned for safe removal during definitive surgery
• Fine needle aspiration is NOT recommended as primary diagnostic modality