2027 L4 Dermatopathology Part 1

Introduction to Dermatopathology

• Overview of dermatopathology, focusing on diagnosis of skin pathologies.

• Series of lectures covering key principles and diagnostic techniques relevant to skin diseases.

• Importance of understanding pathology for assignments in module.

Scope and Importance of Dermatopathology

• Dermatopathology is vital for diagnosing various skin conditions.

• Involves examination of skin diseases at microscopic and molecular levels.

• Dermatologists often rely on histology when visual inspection is insufficient.

Role of Dermatopathologists

• Dermatopathologists specialize in both dermatology and pathology.

• Their expertise aids in accurate diagnoses through classical and special staining techniques.

• These contribute to effective treatment plans for patients.

Structure of the Skin

• Understanding normal skin structure is crucial for identifying pathological changes.

• The integumentary system consists of skin and its appendages (nails, hair, glands, sensory receptors).

Skin as the Largest Organ

• Skin covers approximately 2 square meters in adults and accounts for 8% of body weight.

• Thickness varies: thinnest on eyelids (0.5 mm) to thickest on soles of feet (4 mm).

Functions of the Skin

1. Barrier Protection: Protects against injuries, harmful substances, and infections.

2. Sensory Detection: Perceives touch, temperature, and pain.

3. Temperature Regulation: Maintains homeostasis through sweat and blood vessel dilation.

4. Metabolic Processes: Synthesizes vitamin D upon sunlight exposure.

Types of Skin

• Thick Skin: Found on palms and soles, hairless, designed for pressure/friction.

• Thin Skin: Covers most body areas, usually has hair, includes hairless regions like fingertips and lips.

Layers of the Skin

1. Epidermis: Outermost layer, protective barrier, derives from ectoderm, avascular.

   • Contains dermal papillae that interlock with the dermis to strengthen the junction.

2. Dermis: Comprised of connective tissue, contains blood vessels, nerves, sweat glands, and hair follicles.

   • Papillary Dermis: Upper section, loose collagen, anchors the epidermis.

   • Reticular Dermis: Dense connective tissue, provides structural strength.

3. Hypodermis: Deepest layer, composed of fat for insulation and energy storage.

Cellular Components of the Epidermis

• Keratinocytes: Main cell type, undergo keratinization from basal layer to stratum corneum (28 days).

• Desmosomes: Intercellular connections that maintain structural integrity; can be affected in disease.

• Epidermis Layers:

  • Stratum Basale: Stem cell layer, continuously divides.

  • Stratum Spinosum: Gives spiny appearance, provides strength.

  • Stratum Granulosum: Keratin granules forming a waterproof barrier.

  • Stratum Lucidum: Occasionally seen in thick skin, transparent.

  • Stratum Corneum: Outermost layer, dead flattened keratinized cells.

Specialized Epidermal Cells

• Melanocytes: Produce melanin for UV protection. Interact with keratinocytes through dendritic processes.

• Langerhans Cells: Immune function, antigen presenting cells.

• Merkel Cells: Mechanoreceptors for light touch, concentrated in sensitive skin areas.

Sensory Receptors in the Skin

• Bare Nerve Endings: Detect pain and temperature.

• Encapsulated Nerve Endings: Specialized receptors for touch, pressure, and vibration (e.g., Meissner's corpuscles, Pacinian corpuscles).

Skin Glands

• Eccrine Glands: Most numerous, involved in thermoregulation, release sweat.

• Apocrine Glands: Located in specific areas; moisture-producing glands possibly related to pheromones.

• Sebaceous Glands: Secrete sebum for skin lubrication and protection against microbial infections.

Biopsy Techniques in Dermatopathology

• Essential for diagnosing both benign and malignant skin conditions.

• Different biopsy types include:

  • Incisional Biopsy: Removes part of a lesion for diagnosis.

  • Excisional Biopsy: Entirely removes a lesion, helpful for malignant conditions.

  • Shave Biopsy: For superficial lesions, reducing scarring.

  • Punch Biopsy: Extracts a full-thickness core, useful for autoimmune conditions.

Common Skin Conditions

• Benign: Skin tags, seborrheic keratosis.

• Inflammatory and Autoimmune: Psoriasis, lupus.

• Malignant: Basal cell carcinoma, squamous cell carcinoma, melanoma.

Importance of Early Recognition

• Recognizing premalignant conditions is vital for preventing progression to skin cancer.

• Importance of proper biopsy technique selection to achieve accurate diagnoses.

Histopathological Features and Techniques

• Understanding histological features helps in diagnosing skin conditions.

• Common staining techniques include:

  • Hematoxylin and Eosin (H&E): Standard stain for cellular architecture.

  • Special Stains: Used for identifying microorganisms, fungal elements, or amyloid deposits.

Conditions and Their Histological Characteristics

• Psoriasis: Affected by parakeratosis, hyperkeratosis, thickening and increased mitotic activity in the basal layer.

• Skin Tags: Composed of collagen and blood vessels, diagnosed primarily by H&E stain.

Preparing for Future Lectures

• Upcoming discussions on autoimmune conditions and detailed examination techniques.

• Importance of understanding immunofluorescence for accurate autoimmune diagnosis.