Melanoma Classification and Diagnosis

Study Notes

Clark Levels of Melanoma

Clark Level 1: Intraepidermal location of melanoma.
Clark Level 2: Junctional melanoma, extends up to the interface of the superficial and deep dermis.
Clark Level 3: Involvement from the superficial dermis down through the deep dermis.
Clark Level 4: Melanoma extends to the reticular dermis.
Clark Level 5: Involvement of subcutaneous fat or hypodermis.

Breslow Thickness

Measures the depth of melanoma from the skin surface to the deepest tumor point.
Distance is taken from the superficial epidural granular cell layer to the deepest intradermal tumor cells.

Melanoma Staging

Utilizes Clark Levels and Breslow Thickness together for comprehensive clinical assessment.
Breslow depth indicates the extent of melanoma invasion, while Clark levels provide depth staging.

Onycholysis

Defined as the separation of the nail plate from the nail bed.

Skin Lesions

Papule: Elevated, dome-shaped or flat-topped lesion, typically up to 5 mm, and often discolored.
Acanthosis: Characterized by exaggerated interdigitating papillary dermis, thickened epidermis, and rete ridge changes.
Erosion: Represents a discontinuity of the skin with incomplete loss of epidermis.
Exocytosis: Infiltration of the epidermis by inflammatory or circulating blood cells.

Melanocytic Nevus and Associated Conditions

Freckle (Ephelis): Increased melanocytes to keratinocytes ratio; small (1 mm to several mm), often tan-red.
Lentigo: Oval, tan-brown macules (5-10 mm), may involve mucous membranes.
Dysplastic Nevi: Larger (often >5 mm), uniformly pigmented, possible irregularities in shape and color.

Maturation Sequence of Nondysplastic Melanocytic Nevi

Nevus cells progressively grow from the dermoepidermal junction into the dermis, correlating with oncogene-induced changes.
Features observable include:
- Superficial nevus cells: larger, pigment-producing, grow in nests.
- Deeper nevus cells: smaller, less pigment, appear as cords/single cells.
- Mature nevus cells: fusiform contours, grow in fascicles resembling neural tissue.

Risk Factors for Melanoma

Genetic Predispositions:
- CDKN2A gene mutation in 40% of familial melanoma cases.
- BRAF mutations in 40-50% and NRAS in 15-20% of tumors.
- TERT mutations present in approximately 70% of melanoma cases.
Environmental Factors:
- Ultraviolet radiation (UVR) from sun exposure is a primary risk factor.
- Melanomas typically arise on sun-exposed areas, particularly upper backs in men and backs and legs in women.
Demographics: Lightly pigmented individuals have a higher risk than those with darker pigmentation.

Description

This quiz covers the various levels of melanoma classification, including Clark Levels and Breslow Thickness. It emphasizes the importance of staging in assessing melanoma and includes related topics such as onycholysis and skin lesions. Test your understanding of these essential dermatological concepts.