Dermatologie

Most common malignant skin tumor Etiology:- Sun exposure- Skin types I and II (people with light complexions, red hair, and who sunburn easily)- Nevoid basal-cell carcinoma syndrome (Gorlin syndrome) Clinical presentation:- Localization: Areas of skin exposed to sun (palms, soles, eyelid, nose)- Pearly, indurated and nodular lesion with rolled border that is usually nontender- Central depression (crater) with ulceration- Slowly growing over months to years, very rarely metastasizes Subtypes:- Nodular basal cell carcinoma→ Most common type of BCC→ Lesions: pearly nodules with a rolled border and central depression→ Most common site: face (esp. the nose)- Superficial basal cell carcinoma→ Lesions: flat, eczematous (scaly) plaque with a pearly border→ Most common site: trunk- Pigmented basal cell carcinoma Histopathology:- Palisading nuclei- Tumor cells appear similar to epidermal basal cells Treatment: - Mohs micrographic surgery: The tumor is removed layer by layer, and each layer is examined for tumor cells.- Other options: cryosurgery, laser ablation, and topical chemotherapy with imiquimod or 5-fluorouracil

Benign growths of immature keratinocytes.- Most common benign skin tumor in the elderly population (20%) Histology:- Papillomatosis- Immature keratinocytes with small keratin-filled cysts (horn cysts).- No dyskeratosis Clinical features:- Multiple darkly pigmented papules/plaques, sharply demarcated, and soft- Greasy, wax-like, and 'stuck-on' appearance- May be pruritic or bleed easily- Increase in number and size with time- Localization: trunk, back of the hands, face and neck, and forearms Diagnosis: Lesions are usually easily recognized. If in doubt, a shave or excisional biopsy can be performed to rule out malignancy. Treatment: Not necessary

Hyperkeratosis and hyperplasia of epidermis commonly caused by human papillomavirus 1-3. Localization: elbows, knees, fingers, palmsAppearance: skin-colored or whitish, rough, scaly papules or plaques (sometimes with a cauliflower-like appearance) Histology:- Irregular hyperkeratosis (thickening of the stratum corneum)- Papillomatosis: elongated rete ridges of the epidermis that point towards the center of the wart- Acanthosis Treatment:- Indications: Pain, functional impairment, cosmetic reasons- First-line: salicylic acid; daily application for a few weeks- Alternatives: 5-fluorouracil cream or topical retinoic acid for flat warts- Surgery: Cryotherapy with liquid nitrogen, surgical excision

- Lentigo maligna - Actinic keratosis - Leukoplakia - Bowen's disease and Erythroplasia of Queyrat

A UV-induced precancerous skin lesion that may progress to skin cancer. Etiology: sun exposure (e.g., from working outdoors) Clinical presentation:- Small lesion with rough surface → sandpaper-like texture- Lesions grow and become erythematous and scaly- Occurs on areas of sun-exposed skin Pathology:- Hyperkeratosis- Parakeratosis- Acanthosis- Dyskeratosis: Atypia, increased mitotic rate - Basal membrane intact, no infiltration Prognosis: Lesions may either regress, persist, or progress to squamous cell carcinoma (SCC). Treatment:- Single lesions: cryotherapy with liquid nitrogen- Multiple lesions: 5-fluorouracil (5-FU), imiquimod, photodynamic therapy

Second most common skin cancer after basal cell carcinoma. Etiology:- Malignant transformation of keratinocytes in the stratum spinosum of the epidermis.Risk factors:- Sun exposure (especially among fair-skinned individuals)- Exposure to ionizing radiation, chemical carcinogens (e.g., smoking, arsenic)- Chronic immunosuppression (e.g., HIV, transplant patients who receive immunosuppressive therapy)- Precancerous skin lesions (especially actinic keratosis and Bowen's disease) Clinical features:- Plaque-like, nodular, papillomatous, and/or verrucous- All forms eventually ulcerate. The ulcer typically has everted edges, bleeds easily, inflammed. Location: Most commonly on the face and neck- A typical location is the lower lip.- The overall rate of metastasis is 2%.- Regional metastasis to lymph nodes is more common than hematogenous spread. Marjolin's ulcer: an aggressive form of cSCC that typically develops from areas of chronically damaged skin such as ulcers (e.g., pressure ulcers, osteomyelitis) and scars (e.g., burn scars) Biopsy: - Atypical keratinocytes: polygonal cells with atypical nuclei- Keratin pearls (also called epithelial nests): deposits of keratin that are surrounded by concentric layers of atypical keratinocytes

Highly malignant tumor arising from melanocytes, is the most common life-threatening dermatological disease. Risk factors:- UV radiation exposure- Light skin- Numerous nevi, giant congenital nevi, or inherited skin conditions (e.g., dysplastic nevus syndrome, familial atypical mole, melanoma syndrome, xeroderma pigmentosa) - Immunosuppression Location: Back or chest (common in men), extremities (common in women) Types:- Superficial spreading melanoma: ∼60%→ Braf V600 E, Ras, c-kit- Nodular melanoma: ∼20%- Lentigo maligna melanoma: ∼10%- Acral lentiginous melanoma: ∼5%→ More common in dark-skinned and Asian populations→ Palms, soles, nailbed, mucous membranes- Amelanotic melanoma: Pink or skin-colored nodes → may be difficult to recognize- Uveal melanoma Metastatic melanoma may spread to lymph nodes, liver, lung, brain, and bone. Pathology shows S100-protein positive, epithelioid cells with fine granules in cytoplasm. Treatment: Surgical excision- 0.5 cm safety margin- Other margins: according to Breslow's depth- Immunotherapy: Checkpoint inhibitors (pembrolizumab, natalizumab), IFN-α and IL-2- Targeted therapy: BRAF (vemurafenib), C-Kit (imatinib) and NRAS inhibitors.- Radiation therapy for recurrent or widespread disease Negative prognostic factors:- Male sex, type, localization, and presence of ulcerations- Tumor thickness is the most important prognostic factor.