Disease directory
Proliferating trichilemmal cyst
Published: September 18, 2026Updated: September 18, 2026
Important: Informational content intended for healthcare professionals. It does not replace clinical evaluation or establish a doctor-patient relationship.
Overview
- Names: Proliferating trichilemmal cyst; proliferating hairy tumor; proliferating trichilemmal (pilar) tumor (PTT). Satyaprakash 2007 .
- First description: Jones described in 1966 the entity “proliferating epidermoid cyst”, now recognized as QTP/“Wilson-Jones tumor”. Jones 1966 , Kamal 2021 .
- Epidemiology (typical): Rare lesion; predominates in older women and scalp ; may arise from a pre-existing trichilemmal cyst; malignant transformation is infrequent but possible. F olpe 2003 , Satyaprakash 2007 , Osto 2021 .
- Codes (indicative): ICD-10: L72.1/L72.11 (trichilemmal/pilar cyst); for neoplastic variants use local benign neoplasm/CIHN codes; ICD-11: EK70.1 (trichilemmal cyst).
- Diagnostic checklist (quick)
- Compatible clinical presentation (scalp nodule ± ulceration/growth). Satyaprakash 2007 .
- Biopsy showing trichilemmal keratinization and lobulated-cystic pattern. Folpe 2003 .
- Targeted IHC if in doubt vs SCC: CD34 , p53/Ki-67 , ± calretinin. Chaichamnan 2010
- CT/MRI imaging in large lesions/suspected invasion/lymphadenopathy. Kawaguchi 2021 .
- Classify risk (benign vs MPTT) and indicate complete excision or Mohs . Tierney 2005 ,
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