What are the different types of normal and abnormal skin lesions and their corresponding differential diagnoses?

Normal and Abnormal Skin Lesions: Types and Differential Diagnoses

Understanding the different types of normal and abnormal skin lesions is essential for accurate diagnosis and appropriate management of skin conditions that may impact morbidity and mortality.

Normal Skin Lesions

Normal skin lesions are benign growths that typically do not require treatment unless they cause symptoms or cosmetic concerns:

• Sebaceous Hyperplasia: Asymptomatic, discrete, soft, pale yellow, shiny bumps typically found on the forehead or cheeks near hair follicles with no clinical significance except for cosmetic concerns 1

• Acrochordons (Skin Tags): Extremely common, small, typically pedunculated benign neoplasms that can be treated with simple scissor or shave excision, electrodesiccation, or cryosurgery if symptomatic 1

• Lipomas: Soft, flesh-colored nodules that are easily moveable under the overlying skin, generally benign and asymptomatic 1

• Dermatofibromas: Idiopathic benign proliferation of fibroblasts that typically require no treatment unless there is a change in size or color, bleeding, or irritation from trauma 1

• Cherry Angiomas: Benign vascular lesions that generally do not require treatment 1

• Milia: Small, white, keratin-filled cysts that commonly appear on the face 2

Abnormal Skin Lesions

Abnormal skin lesions may indicate premalignant or malignant conditions that require closer monitoring or intervention:

Premalignant Lesions

• Actinic Keratoses (AKs): Common lesions caused by cumulative sun exposure with progression rates to squamous cell carcinoma reported between 0.025% and 16% 3

• Atypical Moles (Dysplastic Nevi): Melanocytic nevi that indicate a higher risk of melanoma and may rarely transform into malignant melanoma, particularly in patients with dysplastic nevus syndrome or familial atypical multiple mole-melanoma syndrome 3

• Bowen's Disease: A form of squamous cell carcinoma in situ, most probably secondary to the effects of internal carcinogens 4

• Keratoacanthomas: Rapidly growing, squamoproliferative tumors that resemble squamous cell carcinomas; early simple excision is recommended as they may occasionally transform into invasive squamous cell carcinoma 4, 1

Malignant Lesions

• Melanoma: Malignant tumor of melanocytes that often presents as a changing pigmented lesion; early excision is critical for improved survival 5

• Squamous Cell Carcinoma (SCC): Malignant lesion that may develop from precursor conditions like actinic keratoses 5

• Basal Cell Carcinoma: Most common skin cancer, typically presenting as a pearly papule with telangiectasias 5

Inflammatory and Infectious Lesions

• Psoriasis: Characterized by scaling patches and plaques; therapy typically consists of topical emollients and corticosteroids 2

• Atopic Dermatitis/Eczema: May present with scaling patches and plaques or bullous and vesicular changes 2

• Impetigo: Bacterial infection presenting as a bullous eruption or as an erosion with a honey-colored crust 2

• Lichen Sclerosus: Characterized by thinned epidermis with hyperkeratosis, a wide band of homogenized collagen below the dermoepidermal junction and a lymphocytic infiltrate 6

Differential Diagnoses by Lesion Type

For Pigmented Lesions

• Melanoma vs. Benign Nevus: Melanoma can be phenotypically diverse; benign nevi, seborrheic keratoses, pigmented basal cells, hematomas, and vascular growths may mimic melanoma 6

• Seborrheic Keratosis vs. Melanoma: Seborrheic keratoses are benign but may sometimes be confused with melanoma 6

• Pigmented Basal Cell Carcinoma vs. Melanoma: Both can present as pigmented lesions requiring careful examination 6

For Nodular Lesions

• Pyogenic Granuloma vs. Amelanotic Melanoma: Pyogenic granuloma is a rapidly growing nodule that bleeds easily and may be confused with amelanotic melanoma 1

• Epidermal Inclusion Cyst vs. Lipoma: Both present as subcutaneous nodules but have different characteristics on examination 1

• Cutaneous Abscesses vs. Inflamed Epidermoid Cysts: Cutaneous abscesses are collections of pus within the dermis and deeper skin tissues, while epidermoid cysts contain cheesy keratinous material 6

For Ulcerative Lesions

• Furuncles/Carbuncles vs. Cutaneous Abscesses: Furuncles are infections of the hair follicle, usually caused by S. aureus, while carbuncles involve several adjacent follicles 6

Diagnostic Approach

• Physical Examination: Precancerous lesions can be identified by physical examination; diagnostic accuracy is enhanced by dermatoscopy 3

• Biopsy Indications: Biopsy is indicated when definitive diagnosis is deemed necessary for suspicious lesions, particularly those that are growing, spreading, pigmented, or occur on exposed areas of skin 5, 3

• Complete Excision: For melanocytic lesions thought to be malignant, complete excision with a narrow rim (2 mm) of normal skin is the standard practice rather than partial biopsy 6

Management Considerations

• Premalignant Lesions: Early identification and treatment of premalignant lesions will reduce the occurrence of malignant disease 5

• Malignant Lesions: Almost all skin cancers can be cured by early excision or destruction 5

• Surveillance: Should include patient self-examination and regular follow-up skin examinations performed by the physician, especially for patients with risk factors 3

• Risk Reduction Education: Physicians should educate patients about risk factors for skin cancer and risk reduction strategies 5