A 70-year-old woman presents with a pigmented skin lesion on her back that has been enlarging over 6 months. Dermoscopy shows irregular borders, color variegation, and a diameter of 8 mm. Biopsy reveals malignant melanocytes extending beyond the dermoepidermal junction into the papillary dermis. The single most important prognostic factor in this tumor is:

• A Anatomical site of the primary tumor
• B Clark level of invasion
• C Presence of tumor-infiltrating lymphocytes
• D Breslow tumor thickness (depth of invasion in mm) ✓

Explanation

Breslow thickness, measured in millimeters from the top of the granular layer to the deepest invasive tumor cell, is the single most important independent prognostic factor for melanoma. Thicker tumors correlate with higher risk of nodal and distant metastasis and worse survival. The current AJCC staging system for melanoma is primarily based on Breslow thickness for the T category. Clark level has been largely superseded by Breslow thickness in current staging, though mitotic rate is also incorporated.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.