Pilar sheath acanthoma is a
rare, benign follicular hamartoma described first in 1978 by Mehregan
Clinical presentation: Clinically resembles a comedo and is
characterized by a central
pore- like opening plugged with keratin.
Lesion is 5-10mm in
occuring almost always on the upper lip.
Cases have been reported
on other areas of the
head and face.
- Central cystically dilated follicle containing keratinous material;
- Follicle opening to surface;
- Buds of squamous epithelium radiate from the
- Tumour lobules are composed of outer root sheath
- Abundant glycogen in some of the tumour cells ;
- Epidermoid keratinisation ;
- Lesion extends into the dermis or
occasionally into the subcutaneous fat.
Dilated pore (small finger-like projections extending into the
(secondary hair follicles radiate from the wall of the primary
follicle, an outer root sheath, inner root sheath and trichohyaline
granules are noted in the secondary follicles) ;