Skin cysts

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Author: Mikael Häggström [notes 1]

Microscopic evaluation

Major initial clues are:

  • Whether the lining of the cyst is stratified squamous epithelium, non-stratified squamous epithelium, or absence of epithelium (pseudocysts):[1]
  • Location of the cyst.[1]

Stratified squamous epithelium

Relative incidence of cutaneous cysts.[2]
Location Main diagnoses[1]
Face
  • Epidermoid cyst
  • Milium
  • Pigmented follicular cyst (men)
  • Dermoid cyst (along embryonic fusion planes such as lateral eyebrows in infants)
  • Verrucous cyst
Scalp
  • Proliferating trichilemmal cyst
Trunk
Pelvic, anogenital
  • Proliferating epidermoid (infundibular) cyst
Axilla and groin
Preauricular
Upper gluteal cleft and sacrococcygeal area
  • Pilonidal cyst

Non-stratified squamous epithelium

Location Main diagnoses[1]
Face
  • Hidrocystoma
  • Eccrine at lower eyelid and cheek
  • Apocrine at eyelid margin
Suprasternal notch
  • Bronchogenic cyst (infants)
Midline anterior neck
  • Thyroglossal duct cyst
Lateral neck, preauricular, mandibular
  • Brachial cleft cyst (teenagers and young adults)
Lower extremities
  • Cutaneous ciliated cyst (young women)
Labia majora
  • Ciliated cyst of the vulva
Ventral glans and penile shaft
  • Median raphe cyst
Umbilical or periumbilical
  • Omphalomesenteric duct cyst

Absence of epithelium (pseudocyst)

Location Main diagnoses[1] Histology Image
Oral mucosa Mucocele (lower labial)
Dorsal aspect of distal phalanx of finger or toe
  • Digital mucous cyst/pseudocyst
Wrist (and generally other locations close to joints or tendon sheaths) Walls composed of bland fibrous tissue. Histopathology of ganglion cyst wall.jpg
Scaphoid fossa of the ear
  • Pseudocyst of the auricle (adult men)
Sites of surgical trauma
  • Cutaneous metaplastic synovial cyst/pseudocyst

Diagnoses

Epidermoid cyst

Main article: Epidermoid cyst
Epidermoid cyst

Also known as epidermal inclusion cyst (EIC) and sebaceous cyst. Typical findings:[3]

  • 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

Trichilemmal cyst

Trichilemmal cyst.

The constitution of a trichilemmal cyst, from external (top) to internal (bottom):[4]

  • Fibrous capsule
  • Small, cuboidal, dark-staining basal epithelial cells in a palisade arrangement, with no distinct intercellular bridging
  • Swollen pale keratinocytes, which increase in height closer to the interior
  • Solid eosinophilic-staining keratin

There is no granular cell layer (in contrast to an 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. 1.0 1.1 1.2 1.3 1.4 page 1917 in: Bolognia, Jean (2018) (in de). Dermatology . Philadelphia, Pa: Elsevier. ISBN 978-0-7020-6342-8. OCLC 1011508489. 
  2. Pakistan: Kamyab, Kambiz; Kianfar, Nika; Dasdar, Shayan; Salehpour, Zahra; Nasimi, Maryam (2020). "Cutaneous cysts: a clinicopathologic analysis of 2,438 cases ". International Journal of Dermatology. doi:10.1111/ijd.14808. ISSN 0011-9059. 
  3. 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
  4. Anne Elizabeth Laumann. Which histologic findings are characteristic of trichilemmal cyst (pilar cyst)?. Medscape. Updated: Jun 11, 2020,