Epidermoid cyst

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Author: Mikael Häggström [note 1]
Generally presents as a skin cyst. Also known as epidermal inclusion cyst (EIC) and sebaceous cyst.

Microscopic evaluation

Epidermoid cyst
A ruptured epidermoid cyst, with a foreign body reaction including multinucleated giant cells, surrounding keratin fragments. A cyst wall is not necessary for diagnosis in a clinical context of skin cyst.

Typical findings:[1]

  • Stratified squamous epithelium with a granular layer
  • Cyst wall does not contain eccrine glands, sebaceous glands or hair follicles
  • Abundant keratin flakes in cyst lumen
  • Often giant cell granuloma in ruptured cysts, similar to foreign body granuloma

Differential diagnosis

Mainly:

Further information: Skin cyst

Further workup

Look for signs of cyst rupture, which may manifest as inflammation, including granulomas and microabscesses.

Microscopic report

Example:

Scalp skin cyst, excision:
Ruptured epidermoid cyst.

Notes

  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.

Main page

References

  1. V. Claire Vaughan, M.D., Joshua Wisell, M.D.. Skin nonmelanocytic tumor - Cysts - Epidermal (epidermoid) type. pathology Outlines. Topic Completed: 9 May 2019. Revised: 13 December 2019
  2. Anne Elizabeth Laumann. Which histologic findings are characteristic of trichilemmal cyst (pilar cyst)?. Medscape. Updated: Jun 11, 2020,
  3. Punnya V Angadi (2009-06-01). Skin: Pilomatricoma. Atlas of Genetics and Cytogenetics in Oncology and Haematology.

Image sources