squamoid adnexal tumors

Types

 eosinophilic cells
 clear cells
 squamous cells with central keratinization

 (a) Solid lobules of eosinophilic cells :

• pilar sheath acanthoma (connected to crater-like cavity)
• acrospiroma (not connected to crater-like cavity)

 (b) Lobules with clear cells :

• acrospiroma (luminal differentiation)
• trichilemmoma (epidermal connection, peripheral palisading, thick basement membrane)
• sebaceous tumors

 (c) Lobules of squamous cells with central keratinization

• proliferative trichilemmal tumor

References

 from Sternberg: Diagnostic Surgical Pathology, 5th Edition, 2009 http://www.pathologyoutlines.com/topic/skintumornonmelanocyticadnexaltumorsgeneral.html