In an otherwise healthy adult with a dermal epidermal inclusion cyst that appears hypoechoic and non‑vascular on ultrasound, how should it be managed based on its size and symptoms?

Management of Dermal Epidermal Inclusion Cysts

For an asymptomatic dermal epidermal inclusion cyst that appears hypoechoic and non-vascular on ultrasound, observation is appropriate for small lesions (<5 cm), while surgical excision should be considered for symptomatic cysts, those causing discomfort due to size, or lesions showing growth over time. 1, 2

Initial Assessment and Imaging Characteristics

Ultrasound is the first-line imaging modality for characterizing superficial soft-tissue masses including epidermal inclusion cysts. 1 The typical sonographic appearance includes:

• Ovoid or spherical hypoechoic subcutaneous mass with dermal attachment 2, 3
• Scattered echogenic reflectors within the lesion (most common pattern, seen in 42% of cases) representing lamellated keratin debris 3
• Posterior acoustic enhancement (present in 96% of cases) 3
• Absence of internal vascularity on color Doppler in uncomplicated cysts 2, 3
• Size typically <4 cm, though larger variants can occur 2, 4

Critical caveat: If the cyst shows a lobulated contour or develops color Doppler signals, this suggests rupture with granulation tissue formation and may mimic a solid mass requiring further evaluation. 3

Size-Based Management Algorithm

Small Cysts (<5 cm)

• Asymptomatic lesions: Observation with reassurance is appropriate 5
• No routine follow-up imaging required if diagnosis is confident based on characteristic ultrasound features 1, 2
• Patient education about benign nature and low risk of complications

Larger Cysts (≥5 cm) or Growing Lesions

• Surgical excision recommended due to increased risk of:
  • Discomfort from mass effect 2
  • Rupture with secondary inflammation 3
  • Diagnostic uncertainty with atypical features 1

Indications for Surgical Excision

Proceed with excision when any of the following are present:

• Symptomatic lesions causing pain or functional impairment 2
• Progressive growth documented on serial examinations 2, 6
• Atypical ultrasound features including irregular margins, solid components, or vascularity 1, 3
• Patient preference for cosmetic reasons or anxiety about the lesion 2
• Diagnostic uncertainty when imaging features are not characteristic 1

When to Escalate Evaluation

If ultrasound features are atypical or clinical assessment is nonspecific, further imaging with MRI may be warranted before deciding on management. 1 Specifically consider MRI for:

• Deep-seated lesions difficult to adequately evaluate with ultrasound 1
• Cysts showing unexpected vascularity or solid components 3
• Lesions in anatomically complex areas 1

Important pitfall: Do not assume all hypoechoic masses are benign cysts. Ruptured epidermal cysts with granulation tissue can demonstrate vascularity and lobulated contours, potentially mimicking malignant soft-tissue masses. 3 When in doubt, biopsy or excision provides definitive diagnosis.

Post-Procedural Considerations

Be aware that epidermal inclusion cysts can develop as a complication following percutaneous procedures or trauma due to implantation of epidermal cells into deeper layers. 6 If a mass lesion develops months after a procedure in the absence of infection signs, ultrasound evaluation is recommended to assess for this possibility. 6