Pathology of Pilar Sheath Acanthoma

Dr Sampurna Roy MD 2022

Answer - Pilar Sheath Acanthoma

Pilar sheath acanthoma is a rare, benign follicular hamartoma described first in 1978 by Mehregan and Brownstein.

Clinical presentation: Clinically resembles a comedo and is characterized by a central pore - like opening plugged with keratin.

Lesion is 5-10mm in diameter.

Site: Solitary lesion occuring almost always on the upper lip.

Cases have been reported on other areas of the head and face.

Microscopic features:

- Central cystically dilated follicle containing keratinous material;

- Follicle opening to surface;

- Buds of squamous epithelium radiate from the central pore;

- Tumour lobules are composed of outer root sheath epithelium;

- Abundant glycogen in some of the tumour cells ;

- Epidermoid keratinisation ;

- Lesion extends into the dermis or occasionally into the subcutaneous fat.

Differential diagnosis:

1. Dilated pore (small finger-like projections extending into the dermis) ;

2. Trichofolliculoma (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) ;

3. Poroma

Dermatopathology Case 86