Pilar Cyst vs. Pilonidal Cyst: Key Differences
Pilar cysts and pilonidal cysts are completely different entities that share only the word "cyst" in their names—they differ fundamentally in origin, location, pathophysiology, and treatment.
Anatomic Location
Pilar Cyst:
- Occurs predominantly on the scalp (90% of cases), arising in areas with high concentrations of hair follicles 1
- Can rarely occur in other head and neck regions, including the temporal area 1
- May occasionally present in the maxillofacial region 1
Pilonidal Cyst:
- Occurs primarily in the sacrococcygeal region (intergluteal cleft near the tailbone) 2, 3
- Rarely found in other locations such as the umbilicus, axilla, interdigital spaces of hands, or penis 4
- Exceptionally rare on the scalp, typically only following trauma 5
Pathophysiology and Origin
Pilar Cyst:
- Benign lesion arising from hair follicle epithelium (trichilemmal origin) 1
- Represents a true cyst with an epithelial lining derived from the outer root sheath of hair follicles 1
- Grows slowly over time as a self-contained structure 1
- Affects approximately 10% of the population 1
Pilonidal Cyst:
- Acquired inflammatory condition caused by penetration of hair into subcutaneous tissue 3
- Results from chronic inflammation secondary to hair penetration, not a true developmental cyst 2, 3
- Nearly unanimous consensus that it is acquired rather than congenital 3
- Associated with constant friction, direct trauma, or poor hygiene in the affected area 4, 3
Clinical Presentation
Pilar Cyst:
- Presents as a slow-growing, painless subcutaneous mass 1
- Typically asymptomatic unless secondarily infected 1
- Can mimic other pathology (e.g., temporal space infection) and lead to diagnostic confusion 1
Pilonidal Cyst:
- Presents with acute inflammatory signs: pain, local infection, redness, and swelling 4
- Often symptomatic at presentation due to active inflammation 2
- May form abscesses and draining sinuses 4
- Complications include cellulitis and abscess formation 4
Treatment Approach
Pilar Cyst:
- Surgical excision is definitive treatment 1
- Complete removal of the cyst with its epithelial lining
- Low recurrence rate when completely excised 1
Pilonidal Cyst:
- Surgery is the principal treatment method 3
- Multiple surgical options exist: excision with open or closed wound healing, or incision and curettage 3
- Endoscopic treatment using fistuloscopy is a minimally invasive option with good results: mean surgical time 40 minutes, healing time 4 weeks, 7% complication rate, and 9% recurrence rate 2
- Incision and curettage may offer advantages regarding morbidity, healing, recurrence, and cure compared to excision 3
Key Clinical Pitfall
The primary pitfall is confusing these two entirely different conditions based on similar nomenclature. A pilar cyst on the scalp is a benign follicular tumor requiring simple excision, while a pilonidal cyst in the sacrococcygeal region is an acquired inflammatory disease requiring more complex surgical management with attention to recurrence prevention 1, 3. The location alone should immediately distinguish these entities in clinical practice.