Saturday, September 25, 2010

Histopath Diagnosis - An Outline

HistoPath Diagnosis - An Outline   View this Website

Where is the pathology – Epidermis, Dermis, Both or Fat layer
Slide looks like normal skin
Parakeratosis and acanthosis
Parakeratosis with neutrophils
Epidermal acanthosis
Epidermal atrophy
Spongiosis
Acantholysis
Basal vacuolization
Sub epidermal blister or separation
Lichenoid infiltrate
Superficial and deep perivascular infiltrate
Extravasated red cells
Dermal papillary oedema
Nodular dermal infiltrate
Diffuse dermal infiltrate – cells, substances including drugs and organisms
Panniculitis
Tumours
Epidermal cells
Dermal cells

Adnexal structures
Metastases

Introduction


The video below gives you an overview of the site and how we intend to present the material to you. Try increasing the 360 number below to 720 and click on the box with the arrows pointing out to view this video full screen in high definition. Press ESC on your computer to go back to normal. Try pressing pause to let it load a bit if you have a slow connection to have uninterrupted viewing in full screen HD mode!




Medical Dermatopathology on the contrary is much easier! If a rash is red and scaly the pathology will be in the epidermis and the condition will be under the mnemonic PMs PET(AL)  See Dermatology Made Simple for the relevant diseases under this mnemonic.
If the condition is red but non scaly then the pathology is in the dermis or fat tissue and the mnemonic CUL DVA EVIE applies . Again see Dermatology Made Simple.


It has been said that if a particular diagnosis is not in a pathologist's differential diagnosis possibilities for a slide then the diagnosis is likely to be missed! 

The use of these clinical mnemonics makes the likeliehood of that happening much less. The mnemonics can be enlarged a bit more depending on the needs of the person using them. We have a simpler variant for medical students, but steadily more detailed ones for GPs, Dermatologists and Dermatopathologists. 

For a Dermatopathologist look at the path slide to see where the pathology is. Decide if a Tumour or Inflammatory. If Inflammatory and the pathology is in the epidermis then the PMs PET (AL) applies for the clinical diagnosis in most cases. Sometimes interface pathology will irritate or damage the epidermis sufficiently to  cause either epidermal necrosis or vesicles so the Blistering mnemonic ICI should also be considered if these features are seen. 

If the pathology is in the dermis or fat layer then CUL DVA EVIE will give you the clinical diagnosis but the range of possibilities is greater! This range can be cut down by looking for inflammatory reaction Patterns and it is these that we will learn through using this website! Learn the mnemonics and learn to look at a slide to decide if the pathology is epidermal or dermal or in fat and dermatopathology becomes not only manageable but also relatively easy. 












For the Dermatopathologist to really help you , you need to submit an adequate specimen. Your options are punch, shave, incisional or excisional biopsies. You also need to submit a reasonable history of the case and some Differential Diagnoses. The video below looks at the different types of skin biopsies. 




Diagnosing by First Obvious Feature

Often when you look at a path slide an obvious feature catches your eye. It is quite useful to have a list of differential diagnoses for these features. You should still systematically examine a slide in case a less obvious feature is actually present and is of even more importance!

I also like to look at a slide and immediately state whether I think this is an Epidermal or a Dermal histological pattern. I then assign a couple of mnemonics as follows
If Epidermal then the diagnosis will be one of the Red Scaly or Skin Coloured scaly diagnoses and the mnemonic will be the PMsPET a little cat called PETAL

If dermal then the mnemonic will be CUL DVA EVIE

If pustules obvious use II  and if vesicles or blisters use ICI   (See explanation for these mnemonics below.)

So look at the slide, decide whether Epidermal or Dermal or Both, Go through the diseases in the relevant mnemonic and then look for Specific histological features or clues to decide on the likeliest diagnosis. If you need more information on a histopath feature look at Dermpath Diagnosis If you want to see clinical pictures of the skin diseases go to GlobalSkin Atlas. If you need more information on the mnemonics look at Differential Diagnosis


Epidermis.
Parakeratosis
Parakeratotic column
Alternating Ortho and Parakeratosis
Absent stratum corneum
Neutrophils in the stratum corneum
Collections of cells in the epidermis
Thickened epidermis
Thinned epidermis
Thickened basement membrane
Epidermis with Atypical keratinocytes
Dyskeratotic cells
Pale cells in the epidermis
Epidermotropism
Basal layer damage
Pagetoid spread of cells or nests
Follicular pathology

Dermis 
Grenz zone
Papillary oedema
Material laid down
Black staining
Pink staining
Blue staining
Clear cells
Clear spaces between cells
Indian filing of cells between collagen
Cells with anything within them
Papillary microabscesses
Flame figures in the dermis
Busy dermis
Giant cells
Ectopic tissue
Lichenoid infiltrate
Perivascular infiltrate
Mid dermal infiltrate
Desmoplasia
Involvement of fat

Tumours
Blue cells in dermis
Spindled cells
Granular cells
Clear cells
Balloon cells
Excess eccrine ducts
Excess Sebaceous glands
Excess vascular spaces
Keratin cysts in the dermis
Indian filing
Atypical cells with prominent nucleoli

Adapted from Dermatopathology - Diagnosis by first impression. Christine J Ko and Ronald Barr Wiley-Blackwell

The conventional approach to teaching the pathological diagnosis of inflammatory skin disease has been to assign the slide to a particular reaction pattern and look for the subtle features that distinguish one disease from another that conventionally are known to cause that reaction pattern. This works quite well but if you get the reaction pattern wrong you will have trouble arriving at the correct diagnosis. You can combine the first obvious feature with reaction patterns to minimise this risk.


1. Diagnosing skin diseases is not difficult. You look at a rash and decide if it is red and scaly or red and non scaly. If it is red and scaly you use the mnemonic PMs PET (PET is Psoriasis, Eczema and Tinea. This is the Prime Minister'S Pet ( I used to always think of Kevin Rudd with a Siamese cat called Petal sitting on his lap!) The first P of PM is for Pityriasis rosea or Pityriasis versicolour, Pityriasis rubra pilaris, Pityriasis lichenoides and the M is for Mycosis fungoides, a T cell lymphoma of the skin.) The S is for Solar damage and Scabies

 Now we know that his pet cat is called PETAL. This helps us to remember Psoriasis, Eczema and Tinea but also the less common red scaly diseases of A for Annular erythemas and L for Lupus erythematosus ,Lichen Planus, Light eruption and Lues (an old name for syphilis)

2. If it is red but not scaly consider Cellulitis, Urticaria, Lupus, Light eruption, Drug reaction, Viral exanthem or Annular erythema .The mnemonic is C U L at the Department of Veterans Affairs EVIE(your girlfriend Evie) (CUL DVA EVIE) where EVIE stands for Erythema multiforme, Vasculitis and Erythema nodosum and Infiltrates

3. If there are Pustules then the mnemonic is II
(aye aye) Infective( viral, bacterial, fungal) or Inflammatory eg psoriasis or a pustular drug reaction. Common causes include Staph folliculitis , modified fungal infection or if the vesicles are grouped herpes simplex. Pustules on the face are Acne, Rosacea, Staph folliculitis or H Simplex if grouped.

4. If there are Blisters or vesicles The mnemonic is ICI(Imperial Chemical Industries) Inflammatory including Immunological, Contact dermatitis and Infective.
Inflammatory causes can include drugs but remember Immunological causes in the elderly particularly bullous pemphigoid. Contact dermatitis usually gives smaller vesicles rather than blisters but individual vesicles can join up into blisters. If blisters are linear and itchy it is probably a Plant contact dermatitis. Infective blisters are usually bullous impetigo due to a staph infection. If in a dermatomal distribution blisters are likely to be Herpes Zoster.

5. If Skin Coloured and Scaly The mnemonic is ( I am coming Don't go away) Ichthyosis, Acanthosis nigricans, Confluent and Reticulate papillomatosis, Dariers, Grovers and Acrokeratosis verruciformis) but these are mostly uncommon conditions.

6. Skin coloured and Non scaly  No good mnemonic except ICS (Infiltrates of cells or substances)     Most cases are Infiltrates of cells or substances  eg Granuloma annulare, Sarcoidosis, Mucinosis, Scleromyxedema, Scleredema, Scleroderma,  Metastases,

Introduction to skin histopathology

This video will look at the structure of the skin and the cells within it because you really need to know what is normal and be able to recognise the normal cells there before you can appreciate what is abnormal! If you want a more detailed view of skin anatomy have a look at this excerpt from Lever's Textbook

Try increasing the 360 number below to 720 and click on the box with the arrows pointing out to view this video full screen in high definition. Press ESC on your computer to go back to normal. Try pressing pause to let it load a bit if you have a slow connection to have uninterrupted viewing in full screen HD mode!



















Skin Biopsies and the Histopathology Report

Try increasing the 360 number below to 720 and click on the box with the arrows pointing out to view this video full screen in high definition. Press ESC on your computer to go back to normal. Try pressing pause to let it load a bit if you have a slow connection to have uninterrupted viewing in full screen HD mode!
















Check out this excellent review of alternative nail biopsy.








Skin Stains