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Histology of the Normal Skin

Dr Sampurna Roy MD


 
Benign Sweat Gland Tumour

         

http://www.histopathology-india.net/SwTu.htm

 

The skin consists of a keratinised squamous epithelium (epidermis) and a fibroelastic connective tissue layer (dermis) separated by a basement membrane zone (dermal-epidermal junction).

The dermis is attached to underlying loose connective tissue (subcutaneous layer or hypodermis) which contains primarily adipose tissue.

The junction between the epidermis and dermis is characterised by downward folds of the epidermis called epidermal ridges or rete which interdigitate with upward projections of the dermis called dermal papillae.

             

Epidermal layers:

1. Stratum basale
2. Stratum spinosum 
3. Stratum granulosum   
4. Stratum corneum  
         

Dermal layers:

1. Papillary
2. Reticular

Specialized cell of the epidermis: (non-keratinocytes):

1. Melanocytes 
2. Langerhans cells
3. Merkel cells


Epidermal appendages :

Hair follicles
Sebaceous glands
Sweat glands (eccrine and apocrine glands)

Regional variation of skin:

Scalp - The terminal hair follicles extend into subcutaneous fat.

Face - Numerous piloseaceous units are present. Sebaceous  glands are particularly large and prominent on the nose.

Eyelid - The epidermis is thin and there are glands of Moll in the dermis

Trunk - Thicker reticular dermis than elsewhere.

Palms and soles - The stratum corneum is thick and compact. There is no basket weave pattern of keratin and no pilosebaceous units are present in the dermis. 

Lower leg  - Thick walled venules in the papillary dermis due to effects of gravity & stasis. 

Genitalia and areola  - Contain muscle fibres.

NOTE:   Some normal features such as keratinization & dermal thickening occur in inflammatory conditions therefore  site of the biopsy should be taken into account before making any diagnosis.

Hair Follicle:

The hair follicles are cylindrical downgrowth of surface epithelium.

The pilosebaceous unit  consists of follicle, attached smooth muscle (arrector pili muscle) and a sebaceous gland.

 

                                                

Hair follicle is divided into 3 regions:  

     

     

   

1. Lower segment (bulb & suprabulb)-  

Extends from the base of the hair follicle to the insertion of the arrector pili muscle.

2. Middle segment (isthmus) -

Extends from the insertion of the arrector pili muscle to the entrance of the sebaceous gland duct.

3. Upper segment (infundibulum)-  

Entrance of the sebaceous gland duct to the follicular orifice.
The hair bulb encloses dermal papilla.
The hair follicle consists of five concentric layers:

1. Medulla
2. Cortex
3. Cuticle
4. Internal root sheath
5. External root sheath

 March 2014

Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)

 

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Benign sweat  gland tumours

Cysts:

Hydrocystoma -Eccrine/Apocrine

Hamartomas:

Eccrine/Apocrine naevus

Eccrine  Angiomatous Hamartoma

Porokeratotic   eccrine ostial naevus

Benign Neoplasms:

Syringo cystadenoma Papilliferum

Hidradenoma Papilliferum

Nipple Adenoma

Syringoma

Spiradenoma

Cylindroma

Chondroid Syringoma (benign mixed tumour)

Poroma

Hidradenoma

Apocrine adenoma

Papillary eccrine adenoma

Syringo fibroadenoma

Malignant sweat gland tumour 

Low grade:

Microcystic adnexal carcinoma

Eccrine epithelioma

Adenoid cystic carcinoma

Mucinous  carcinoma


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