Causes of a Single Cyst on the Labia Minora
A single cyst on the labia minora is most commonly a Bartholin duct cyst or an epidermal (epidermoid) inclusion cyst, with Bartholin duct cysts being the most frequent vulvar cystic lesion overall. 1
Primary Etiologies
Bartholin Duct Cyst
- Bartholin glands are located at the base of the labia minora and produce vaginal lubrication. 1
- Ductal obstruction leads to accumulation of secretions and cyst formation, affecting approximately 2% of women during their lifetime. 1
- These typically pea-sized glands can enlarge significantly when blocked, forming cysts that may range from small to several centimeters. 1
- The cyst may become secondarily infected, progressing to a Bartholin gland abscess with associated pain, erythema, and potential systemic symptoms. 1
- Rare complications include fistula formation, though this is exceptionally uncommon. 2
Epidermal (Epidermoid) Inclusion Cyst
- Epidermal cysts on the labia minora are rare but well-documented, representing the first anatomic site after labia majora and clitoris for vulvar epidermal cysts. 3
- These cysts result from implantation of epithelial elements into the dermis, often following trauma, episiotomy, or spontaneous epithelial inclusion. 3
- They typically present as painless, slowly growing masses that may cause discomfort with walking or sexual activity when enlarged. 3, 4
- Definitive diagnosis requires histopathological examination after surgical excision. 3
Less Common Causes
Mucous Cysts
- Can arise from minor vestibular glands in the labia minora region
- Usually small and asymptomatic
Labial Fusion-Related Pseudocysts
- Periclitoral or labial pseudocysts may form in patients with labial fusion from conditions like lichen sclerosus, lichen planus, or childhood agglutination. 5
- These present with recurrent cyst formation, pain, and discharge. 5
Diagnostic Approach
Physical examination should specifically assess:
- Cyst location relative to the Bartholin gland opening (posterolateral aspect of vaginal introitus at 4 and 8 o'clock positions). 1
- Size, consistency, tenderness, and presence of erythema or fluctuance (suggesting abscess formation). 1
- Mobility and relationship to surrounding structures. 3
For larger masses (>5-6 cm), MRI is valuable for:
- Precise anatomic localization and relationship to adjacent tissues. 3
- Treatment planning prior to surgical intervention. 3
Critical Management Considerations
- Surgical excision provides definitive histopathological diagnosis and prevents future complications, particularly for epidermal cysts. 3
- For Bartholin duct cysts, simple needle aspiration or incision and drainage are NOT recommended due to high recurrence rates. 1
- Preferred office-based treatments for Bartholin cysts include marsupialization, Word catheter placement, or sclerotherapy, all with similar healing and recurrence rates. 1
- Malignancy is exceedingly rare in labial cysts but should be considered in the differential diagnosis, particularly in postmenopausal women or with atypical features. 6