Introduction to dermatopathology

Introduction to Dermatopathology

Peter Pavlidakey, MD

Definition of Dermatopathology

• Subspecialty of dermatology and pathology focused on performing and interpreting tests on human tissue samples to provide scientific data and consultative opinions to referring clinicians

• Interpretation of skin biopsies

Dermatopathology thought process

• Clinical problem

• Biopsy planning

• Biopsy technique

When to perform a skin biopsy

• What can a skin biopsy tell us?

• What are the limitations?

• How do these limitations apply to the clinical scenario?

When to perform a skin biopsy

• When is a skin biopsy most likely to be fruitful?

– When it is performed to investigate a focused hypothesis

Example: biopsy for alopecia

• Why is she losing her hair?

• Is the etiology of this patient’s hair loss lupus erythematosus or lichen planopilaris?

Example: Dermatitis

• Why is this patient’s rash not responding to therapy

• Biopsy out of need

• Is our presumed clinical diagnosis correct or are we in fact dealing with another process?

• Prior therapy?

When is a biopsy least likely to yield useful information?

• The biopsy without a clinical hypothesis or in which the clinical hypothesis is not communicated to the dermatopathologist

Biopsy planning

• Where to biopsy

• How to biopsy

Where to biopsy

• Biopsy the area most likely to distinguish among the considerations or most likely to confirm the primary consideration.

Where to biopsy: NMSC

• Preferable to sample entire lesion

• Sample lesion and adjacent normal skin

• Sample entire deep edge of small lesions

Best

Better

Worst

Good

Where to biopsy: Rash

• Sample border of process and unaffected skin

• Different morphologies? – Consider multiple samples

• Prefer new lesions for most conditions –exceptions exist – no substitute for knowledge of process being sampled

Worst

BetterBest

Where to biopsy: Blister

Biopsy of pigmented lesions

• Dysplastic nevus vs melanoma: elipse, punch, or “scoop” shave – at least 1 mm!

• Try to avoid transecting lesion – peripheral or deep

• Shave-punch vs double shave

• What information will the surgeon and oncologist need?

Classification Thickness Ulceration/Mitosis

T1 ≤1.0 mm A: w/o ulceration and mitosis < 1/mm²B: with ulceration or mitosis ≥ 1/mm²

T2 1.01- 2.0 mm A: w/o ulcerationB: with ulceration

T3 2.01- 4.0 mm A: w/o ulcerationB: with ulceration

T4 >4.0 mm A: w/o ulcerationB: with ulceration

Melanoma Staging

Types of sampling

• Shave

• Punch

• Ellipse

• Curettage

• Extraction

• Fine needle aspiration

• Scraping

• Special sampling for hair and nail

Shave biopsy: definition

• Horizontally transects the epidermis

• Usually with a specialized flexible blade or small scalpel

• Deep shave often referred to as saucerizationor “scoop”

Shave biopsy: Advantages and limitations

• Breadth and depth can be tailored infinitely to the process being sampled

• Ideal for sampling processes restricted to the epidermis and superficial dermis

• Usually neoplasms

• Neoplastic conditions with findings restricted to the epidermis which can be sparse: mycosis fungoides, superficial EAC, PUPPP, etc.

• Potentially excellent cosmesis

Punch biopsy

• Uses a specialized cylindrical instrument to vertically transect all levels of the skin

• 1 mm to 1 cm

• Often used to sample dermatitis and selected neoplasms

Punch biopsy: Advantages and limitations

• Potentially samples all layers of the skin

• Much quicker than ellipse

• Variety of sizes available: balance sampling and cosmesis

• Potential to under sample and miss sparse findings

Punch biopsy: Tips and techniques

• Use the smallest size which will adequately sample the disease process

• Use 6 mm or larger to sample subcutis

• Never sample suspected panniculitis with 2 mm punch!

• >3 mm preferred to sample dermatitis

• Do not use crushing instruments to extract the sample

Ellipse

• Incision to subcutis

• Incisional or excisional

Ellipse: Advantages and limitations

• Greatest potential for one step management

• Excellent cosmesis with good technique and planning

• Least likely to yield false negative or uninformative result

If all else fails…

• Use shaves to sample neoplasms

• Use punches to sample rashes

• Consider elliptical excisional biopsy to sample when suspicion for malignancy is high.

Specimen labeling and handling

• Patient identifiers in duplicate

• Precise site designation in duplicate

• State the clinical hypothesis

• Indicate type of procedure and intent of procedure

• Indicate desire for margin evaluation

• Minimize requests of adjuvant diagnostic testing

Submit a clinical photo

Thank you

Dr Kim Hiatt Dr Peter Pavlidakey