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Pathology of Pilar Sheath


Dr Sampurna Roy MD

Dermatopathology Case 86

Diagnosis: Pilar Sheath Acanthoma


February 2016


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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 .

Further reading:

Postauricular pilar sheath acanthoma.

Pilar sheath acanthoma.

Pilar sheath acanthoma--report of a case with review of the literature.

Pilar sheath acanthoma - a benign follicular hamartoma. 

Pilar sheath acanthoma. A new benign follicular tumor.

Pilar Sheath Acanthoma. 

Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)


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