Proliferating trichilemmal cyst

Proliferating trichilemmal cysts are dermal or subcutaneous tumors with squamoid cytologic features and trichilemmal-type keratinisation usually arising in the scalp.

A variety of names have been used for this pathology, including proliferating epidermoid cyst, pilar tumor of the scalp, proliferating trichilemmal cyst, proliferating epidermoid cyst, giant hair matrix tumor, hydatidiform keratinous cyst, trichochlamydocarcinoma, and invasive hair matrix tumor 1.

Proliferating trichilemmal cysts have female predominance 3,4.

Proliferating trichilemmal cysts present as lobulated masses within the scalp. They vary considerably in size from a few millimeters to large masses many centimeters in diameter. Occasionally clinical presentation will be with superimposed infection or malignant transformation, although both of these complications are uncommon 3

Although they are mostly benign, they have local invasive and malignant types 2. They show extensive epithelial proliferation, variable cytologic atypia and mitotic activity.

Proliferating trichilemmal cysts usually are located within the scalp and appear as multiple complex subcutaneous solid or cystic masses. The cystic components contain high-density proteinaceous material which sometimes layers dependently 3. Ring-like patterns of mineralisation are also encountered 3

Proliferating trichilemmal cysts were first defined by Edward Wilson Jones, an English dermatopathologist, in 1966 2

In some situations, consider an epidermal inclusion cyst

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Article information

rID: 56540
System: Head & Neck
Synonyms or Alternate Spellings:
  • Pilar tumor of the scalp
  • Hydatidiform keratinous cyst
  • Proliferating epidermoid cyst
  • Giant hair matrix tumour
  • Proliferating trichilemmal tumour

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