Dermatopathology

Dermatopathology is the pathology of skin.

Pathology is a significant part of dermatology and dermatologists spend five years in residency. So, it is a huge area.

Layers of the skin

• Epidermis - outer most layer, avascular, separated from dermis by a basement membrane, epithelial tissue.
• Dermis - below the epidermis, vascular, separated from the epidermis by a basement membrane, connective tissue.
• Subdermis - below the dermis, connective tissue.

Layers of epidermis

Epidermis layers - from the surface to epidermal-dermal junction:

• Stratum corneum.
• Stratum lucidum.
• Stratum granulosum.
• Stratum spinosum (aka prickle layer).
• Stratum basale (germinativum).

Mnemonic: Corn Lovers Grow Several Bales.

Common terms

• Acanthosis = thickening of the prickle layer (stratum spinosum) of epidermis.
• Parakeratosis = retention of nuclei in the stratum corneum, normal in mucous membranes
• Dyskeratosis = abnormal keratinization, often refers to keratinization below the stratum granulosum; keratinization above may be abnormal (dependent on body site).

Adnexal structures

• Ecrine glands - spindle-shaped myoepithelial cells surround luminal cells.
• Ecrine ducts - cuboidal type subepithelial cells.

Ref.:

Skin diseases

Cancer

Main article: Dermatologic cancer

Skin cancer is very common. The basic DDx of a malignant skin lesion is:

• Squamous cell carcinoma.
• Basal cell carcinoma.
• Malignant melanoma.
• Metstases.

Non-malignant disease

Main article: Non-malignant skin disease

Non-malignant skin disease is common. It is the domain of dermatologists. It can be scary for general anatomical pathologist because the differential diagnosis is often broad, and, it's generally not something the general anatomical pathologist sees a lot of.

Presentations

Leukoplakia

DDx:

• Vitiligo (loss of pigment).
• Inflammation.
  • Chronic dermatitis.
  • Psoriasis.
• Neoplasia.
  • Vulvar intraepithelial neoplasia.
  • Paget disease.
  • Invasive carcinoma.
• Other.
  • Lichen sclerosus.
  • Lichen simplex chronicus.

Skin disease and systemic conditions

• Acanthosis nigricans: diabetes mellitus.
• Dermatitis herpetiformis: gluten enteropathy (celiac disease), thyroid disease, intestinal lymphoma.
• Pemphigus vulgaris: thymoma, myasthenia gravis, malignancy.

Inverted follicular keratosis

• Benign skin lesions.
  • May mimic squamous cell carcinoma or basal cell carcinoma.