What causes an epidermoid cyst to grow?

Causes of Epidermoid Cyst Growth

Epidermoid cysts grow primarily due to the continuous accumulation of keratin material from the cyst lining, which occurs when there is obstruction of a pilosebaceous follicle. 1

Primary Causes of Growth

• Follicular Obstruction: Epidermoid cysts originate from the follicular infundibulum, which when obstructed by keratin, results in cyst formation and continued growth 2

• Keratin Accumulation: The cyst wall continuously produces keratin material that accumulates within the cyst cavity, causing gradual enlargement 1

• Incomplete Removal: Previous incomplete removal of a cyst wall is a major factor in recurrence and continued growth, with recurrence rates ranging from 2.2-8.3% 1

Secondary Factors That Accelerate Growth

Inflammation and Infection

• Rupture-Induced Growth: Inflammation often occurs as a reaction to rupture of the cyst wall and extrusion of its contents into the dermis, which can accelerate growth 1

• Infection: Secondary infection of the cyst can cause rapid enlargement and pain

  • Common pathogens include Staphylococcus aureus and streptococci 1
  • Infected cysts are more difficult to excise, and it's often preferable to postpone excision until inflammation has subsided 3

Trauma

• Physical Trauma: Injury to the cyst can cause rupture of the cyst wall, leading to inflammation and accelerated growth
• Manipulation: Repeated attempts to express the contents without removing the cyst wall can lead to inflammation and faster growth

Warning Signs of Concerning Growth

Pay attention to these features that may warrant further investigation:

• Rapid Growth: Sudden enlargement may indicate infection or, rarely, malignant transformation
• Suspicious Features: Nodular mass, ulceration, extensive scarring, or localized crusting 1
• Size >1.5 cm: Larger cysts should be evaluated pathologically 1
• Fixation to Surrounding Tissues: May indicate either inflammation or, rarely, malignant change 1

Management Considerations

For growing epidermoid cysts:

• Non-inflamed Cysts: Complete surgical excision with removal of the entire cyst wall is recommended to prevent recurrence, with a minimum 4-mm margin around the cyst border 1

• Inflamed Cysts: Incision and drainage is the definitive treatment, with antibiotics only necessary when there are signs of systemic inflammatory response syndrome or in immunocompromised patients 1

• Minimal Excision Technique: Less invasive than complete surgical excision, involves making a 2-3 mm incision, expressing the cyst contents, and extracting the cyst wall 3

• Emerging Treatments: Intralesional administration of hydrolytic enzymes (hyaluronidase, collagenase, and lipase) represents an innovative technique for management of epidermoid cysts, though further studies are needed 2

Important Caveats

• Histopathological examination is recommended for cysts with suspicious features or unusual clinical presentation to rule out potential malignancy 1
• Incomplete removal of the cyst wall is the main cause of recurrence, emphasizing the importance of complete excision 1
• Inflamed cysts are difficult to excise, and it's often preferable to postpone excision until inflammation has subsided 3