Histological Structure of Skin and Dermatopathology

Comprehensive practice flashcards covering skin histology, primary lesions, microscopic pathology, and skin oncology based on the lecture transcript.

Epidermis

The outermost layer of the skin, consisting of layers like the stratum corneum, granular layer, Malpighian layer, and basal cell layer.

Langerhans cells

Dendritic cells originating from myogenic bone marrow cells, located in the upper part of the stratum spinosum (Malpighian layer).

Merkel cells

Specialized cells found within the basal cell layer of the epidermis, involved in sensory perception.

Macule (Makula)

A flat lesion at the level of the skin; examples include vitiligo (white) and ephelides (brown).

Papule (Papula)

A raised skin lesion with a diameter up to $5\,mm$ (e.g., molluscum contagiosum).

Plaque (Plak)

A raised skin lesion > 5\,mm in diameter, often formed by the merging of papules, as seen in psoriasis.

Nodulus (Nodule)

A lesion that protrudes above the surrounding skin but also extends into the dermis or subcutis (e.g., cysts and tumors).

Vesicle (Vezikula)

A raised lesion up to $5\,mm$ in diameter filled with fluid (e.g., herpes simplex).

Bulla

A fluid-filled vesicle larger than $5\,mm$ in diameter, common in burns, pemphigus, and pemphigoid.

Acantholysis (Akantoliza)

An intraepidermal split, vesicle, or bulla caused by the loss of intercellular connections.

Acanthosis (Akantoza)

A thickening of the epidermis.

Hyperkeratosis

A thickening of the stratum corneum (horny layer) of the epidermis.

Parakeratosis

The presence of nuclei within the stratum corneum (horny layer) of the epidermis.

Spongiosis (Spongioza)

The widening of intercellular spaces between epidermal cells due to edema.

Naevus flammeus (Wine stain)

A congenital vascular lesion most commonly found on the face.

Albinism

An autosomal recessive hereditary disease where the number of melanocytes is normal but they are unable to produce melanin.

Solar keratosis (Actinic keratosis)

A precancerous lesion caused by long-term sun exposure that may progress to planocellular carcinoma.

Impetigo

A bacterial infection caused by Staphylococcus aureus appearing as pustules on an erythematous base, common in children.

Erysipelas (Erzipel)

A purulent cellulitis of the dermis and superficial subcutis caused by beta-hemolytic streptococcus, characterized by tense, red skin.

Herpes zoster

A viral infection caused by the reactivation of the varicella virus from ganglia, resulting in painful vesicles along a nerve path.

Molluscum contagiosum

An umbilicated papule caused by the pox virus, characterized by basophilic viral inclusions called molluscum bodies.

Pemphigus

An autoimmune disease where antibodies target surface antigens of keratinocytes (desmoglein 3), causing intraepidermal bullae.

Psoriasis

A chronic, recurring disease showing scaly plaques, acanthosis, parakeratosis, and pinpoint bleeding known as the Auspitz phenomenon.

Auspitz phenomenon

Point-like bleeding that occurs after the peeling of a psoriatic plaque.

Leser-Trélat phenomenon

The sudden appearance of multiple seborrheic keratoses, which may be a paraneoplastic sign of gastrointestinal carcinoma.

Basalioma (Basal cell carcinoma)

A type of skin cancer also known as Ulcus rodens that never metastasizes.

Gorlin syndrome

A condition involving multiple basaliomas and internal organ neoplasms due to a mutation in the PATCH tumor suppressor gene.

Breslow depth

A staging method for melanoma based on tumor thickness in $mm$; each stage increases by $0.76\,mm$.

Clark level

A staging method for melanoma based on the specific layer of skin the tumor has infiltrated.

Superficial spreading melanoma (SSM)

The most common type of melanoma ($70\%$), showing biphasic growth and pagetoid melanocytes.

Nodular melanoma (NM)

A melanoma showing only vertical (monofasic) growth, often appearing de novo as epithelioid cells.

Acral lentiginous melanoma (ALMM)

A type of melanoma found on palms, soles, or under nails, more common in colored races.

CDKN2A

The gene for cyclin-dependent kinase 2A, which is mutated in $40\%$ of patients with dysplastic nevoid syndrome and melanoma.

Merkel cell carcinoma

A neuroendocrine skin carcinoma appearing on sun-exposed areas that rapidly metastasizes to lymph nodes, brain, and lungs.

Mycosis fungoides

A primary T-cell lymphoma of the skin.