Dermatopathology 1 Lecture PDF

Dermatopathology 1 Dermatopathology is a branch of pathology that focuses on the study of skin diseases through the examination of skin tissue under a microscope. Specialists in this field analyze skin samples (such as biopsies) to diagnose various ski...

Dermatopathology 1 Dermatopathology is a branch of pathology that focuses on the study of skin diseases through the examination of skin tissue under a microscope. Specialists in this field analyze skin samples (such as biopsies) to diagnose various skin conditions, including skin cancers, infections, inflammatory disorders, and genetic skin disorders. PATHOLOGY II Dermatopathologists examine microscopic tissue changes to detect abnormalities or damage in the skin cells and tissues, helping in the accurate diagnosis of skin diseases. 8/12/2024 First 2024/2025 Dr KHALID SOBHI MOWAQET 9 week  Upon completion this lecture the students should define and understand the following terms and items Define and understand primary and secondary skin lesions Define and understand some important non cancerous lesions of the skin such as 1. Acute Inflammatory Dermatoses (Acute Eczematous Dermatitis) 2. Infectious Dermatoses (Impetigo) 3. Chronic inflammatory dermatosis (Psoriasis) (Acne vulgaris) (Lichen Planus) 4. Allergic dermatitis (Erythema multiform) 5. Seborrheic dermatitis 2  What are a primary & secondary skin lesions? Primary skin lesions Secondary skin lesions originate on previously healthy develop from the evolution of a primary skin skin and are directly associated lesion, either due to traumatic manipulation, with a specific cause. such as scratching or rubbing, or due to its treatment or progression Examples of primary skin lesions include freckles, Examples of secondary skin lesions include moles, crusts, and blisters ulcers, and scars. 3 4  Acute Inflammatory Dermatoses NON-INFECTIOUS INFLAMMATORY DERMATOSES 1 1. Acute Eczematous Dermatitis Definition: inflammatory response to a variety of agents acting on the skin from outside or from within the body such as chemicals and drugs. 3 2 Based on initiating factors, eczematous dermatitis can be subdivided into the following categories: (1)Allergic contact dermatitis, (2) Atopic dermatitis, (3) Drug-related eczematous dermatitis, (4) Primary irritant dermatitis. 5 4  Pathogenesis Eczematous dermatitis typically results from T cell– mediated inflammatory reactions (type IV hypersensitivity). Type IV hypersensitivity is a type of delayed-type immune response, in which the immune system responds to an antigen several hours or days after exposure. It is also known as cell-mediated hypersensitivity because tissue damage involves T cells (interaction of T cells with antigens) 6  Morphology Eczematous dermatitis is characterized by considerable spongiosis (intercellular edema) that may lead to formation of intraepidermal vesicles or bullae. The vesicles and bullae as well as the edematous epidermis are spread by acute inflammatory cells. The upper dermis shows congested blood vessels and mononuclear inflammatory cell infiltrate, especially around the small blood vessels 7  2. ERYTHEMA MULTIFORME (EM) Is a skin self-limited disorder that's considered to be an allergic reaction to medicine or an infection. Causes This disorder is associated with the following conditions: (1)Infections such as (herpes simplex), (2) administration of certain drugs (penicillin) (3) malignant disease (carcinomas and lymphomas); (4) collagen vascular diseases (lupus erythematosus). 8 Clinical features Affected individuals present with an array of “multiform” lesions, including Macules, Papules, Vesicles, and Bullae as well as the characteristic target lesion consisting of a (red macule or papule with a pale, vesicular, or eroded center) Symmetrical involvement of the extremities frequently occurs. An extensive febrile form of the disease, (Stevens- Johnson syndrome) also may occurs. Typically, erosions and hemorrhagic crusts involve the lips, conjunctiva and oral mucosa, 9  ACNE VULGARIS Acne vulgaris is a very common chronic inflammatory dermatosis found predominantly in adolescents in both sexes. The lesions are seen more commonly on the face, upper chest and upper back How acne develops? Acne develops when sebum — an oily substance that lubricates the hair and skin — and dead skin cells plug hair follicles. then Bacteria can trigger inflammation and infection resulting in more severe acne It is believed to occur as a result of physiologic hormonal (Androgen) 10  Pathogenesis The condition affects the hair follicle, the opening of which is blocked by keratin material resulting in formation of comedones. Comedones may be open having central black appearance due to oxidation of melanin called black heads, or they may be in closed follicles referred to as white heads. A closed comedone may get infected and result in pustular acne 11  1. IMPETIGO. Is a common superficial bacterial infection caused by staphylococci and streptococci. The condition may commonly involves hands and face. The lesions appear as vesico-pustules which may rupture and are followed by characteristic yellowish crusts. (circumscribed, elevated lesion filled with purulent fluid) Histologically, the characteristic feature is the collection of neutrophils under the stratum corneum. Often, a few acantholytic cells and gram-positive bacteria are found 12 within the pustule  2. VERRUCAE (WARTS). Verrucae or warts are common viral lesions of the skin. They are caused by human papillomaviruses (HPV) a type of DNA oncogenic virus Infection with HPV is acquired by direct contact Depending upon the clinical appearance and location, they are classified into different types the most important are. i) Verruca vulgaris is the most common human wart, commonly caused by HPV-1 and The lesions are often multiple, less than 1 cm in size, firm, papules occurring on the dorsal surfaces of hands and fingers. 13  ii. Condyloma acuminatum or venereal wart occurs on the genital organs, anus and oral cavity they are commonly caused by HPV-6. The lesions appear as soft, mass that may grow fairly large in size transformation into verrucous carcinoma may occur 14  Psoriasis Psoriasis is a chronic inflammatory dermatosis that appears to have an autoimmune basis. It usually appears first between the age of 15 and 30 years. The lesions are characterized by brownish-red papules and plaques covered with fine, silvery white scales. As the scales are removed by gentle scrapping, fine bleeding points appear termed Auspitz sign. Commonly involved sites are the scalp, upper back, sacral region and extensor surfaces of the extremities, especially the knees and elbows. 15  Histologically, the following features are observed in fully- developed lesions i) Acanthosis with down growth of rete ridges ii) Elongation and edema of the dermal papillae with broadening of their tips. iii) Absence of granular cell layer. iv) Prominent parakeratosis. v) Presence of Munro microabscesses in the parakeratosis horny layer is diagnostic of psoriasis 16  Lichen Planus Is a chronic dermatosis characterized clinically by irregular, shining, pruritic papules. The lesions are distributed symmetrically with sites of predilection being flexor surfaces of the wrists, forearms, legs, external genitalia and Buccal mucosa Pathogenesis It is possible that expression of altered antigens in basal epidermal cells or the dermoepidermal junction elicits a cell- Histologically, mediated cytotoxic (CD8+) T-cell response. the features are i) Marked hyperkeratosis. ii) Focal hypergranulosis. iii) Irregular acanthosis iv) Basal layer liquefactive degeneration v) A band-like dermal infiltrate of mononuclear cells, 17  SEBORRHEIC DERMATITIS Is a chronic inflammatory dermatosis even more common than psoriasis, affecting 1% to 3% of the general population. It classically involves regions with a high density of sebaceous glands, such as the scalp, forehead, and auricular area, The etiology of seborrheic dermatitis is unknown. However, recent studies suggest that the lesion has fungal etiology Clinical features: The individual lesions are macules and papules on an erythematous-yellow, often greasy base, Dandruff is the common clinical expression of seborrheic dermatitis, particularly behind the ears. 18