Pilar cyst

Pilar cyst, also known as a trichilemmal cyst, is a common benign skin cyst.

General

Very common.
Benign.

Gross

Classic location: head ~90%.^[1]

Microscopic

Features:^[2]

Keratin.
Cyst lining:
- Has no granular layer - key feature.
  - Keratohyaline granules (as seen in the granular layer) may be seen focally.
- Inner most cyst lining cells are large cells with abundant eosinophilic cytoplasm.

DDx:

Epidermal cyst - has a granular layer.

Images

Trichilemmal cyst - intermed. mag. (WC)
Trichilemmal cyst - very high mag. (WC)

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SCALP (CYST), EXCISION:
- TRICHILEMMAL CYST (PILAR CYST).

SKIN CYST, LEFT FLANK, EXCISION:
- TRICHILEMMAL CYST (PILAR CYST).

SCALP (CYST), ANTERIOR, EXCISION:
- TRICHILEMMAL CYST (PILAR CYST), RUPTURED.

Micro

The sections show a cyst that is lined by squamous epithelium without a granular layer. Focally, keratohyaline granules are seen in the cyst lining cells. The innermost cyst lining cells are large and have abundant eosinophilic cytoplasm. The cyst contains keratin.

References

↑ URL: http://emedicine.medscape.com/article/1058907-overview. Accessed on: 15 April 2012.
↑ Busam, Klaus J. (2009). Dermatopathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Saunders. pp. 309. ISBN 978-0443066542.

[1] URL: http://emedicine.medscape.com/article/1058907-overview. Accessed on: 15 April 2012.

[Ref_Derm309-2] Busam, Klaus J. (2009). Dermatopathology: A Volume in the Foundations in Diagnostic Pathology Series (1st ed.). Saunders. pp. 309. ISBN 978-0443066542.

[1]

[2]

Pilar cyst

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