Sebaceous Cysts and Size Fluctuation
True sebaceous cysts (more accurately termed epidermoid or epidermal cysts) do not typically fluctuate in size—they either remain stable or gradually enlarge over time. This is fundamentally different from functional ovarian cysts, which can wax and wane.
Key Characteristics of Sebaceous Cysts
Sebaceous cysts are benign encapsulated subepidermal nodules filled with keratin material that demonstrate progressive growth patterns rather than cyclical size changes. 1
- These cysts are lined by stratified squamous epithelium and contain keratin debris and cholesterol, creating a stable structural lesion 2
- They commonly occur on hairy areas including the scalp, face, neck, back, and scrotum 1, 2
- The cysts typically remain asymptomatic and gradually progress in size over months to years 3, 4
Growth Pattern vs. Fluctuation
The natural history of epidermoid cysts involves slow, progressive enlargement rather than size fluctuation:
- Cases document cysts present since childhood that gradually progressed to enormous sizes (up to 10cm x 8cm) over decades 3
- A 75-year-old patient presented with a colossal epidermal cyst on the upper back that had grown progressively over time 4
- Multiple sebaceous cysts can remain present for several months to years, maintaining or increasing their size 2
Important Clinical Distinction
The term "sebaceous cyst" is actually a misnomer—these are epidermoid cysts, not true sebaceous gland lesions. 1
- Epidermoid cysts contain cheesy keratinous material with normal skin flora even when uninflamed 1
- When inflammation occurs, it results from rupture of the cyst wall and extrusion of contents into the dermis, not from infection 1
- This inflammatory response may cause temporary swelling, but this represents acute inflammation rather than true size fluctuation 1
Clinical Management Implications
Effective treatment requires complete excision of the cyst wall to prevent recurrence:
- A minimal-incision technique demonstrated only 0.66% recurrence rate over 18 months when the entire cyst was properly removed 5
- Incomplete removal leads to recurrence, as documented in cases where initial excision was followed by cyst reformation 6
- For infected or inflamed cysts, incision and drainage alone is insufficient—complete excision is necessary 1
Malignant Potential
While malignant transformation is exceedingly rare, long-standing cysts should be monitored: