Re-evaluation of the Anatomical Distribution Patterns in Large Congenital Melanocytic Nevus.

Area of Science:

• Dermatology
• Medical Genetics
• Developmental Biology

Background:

• Large congenital melanocytic nevi (LCMNs) are classified by distribution patterns, potentially reflecting embryological development.
• Current classification systems for LCMNs exist but require validation in larger cohorts.

Purpose of the Study:

• To assess the clinical validity of existing classification systems for LCMNs.
• To identify potential new patterns or sub-patterns in LCMN distribution.

Main Methods:

• Retrospective cohort study of 111 LCMN patients.
• Analysis focused on the anatomical distribution of the nevus's main mass.
• Evaluation against established 6B and 7B classification systems.

Main Results:

• The trunk was the most frequently affected area, followed by lower extremities.
• Most cases aligned with the 6B/7B classification patterns (bolero, back, bathing trunk, breast/belly, body extremity, bonce).
• Identified potential new sub-patterns: 'hood' (head/neck), 'half-bathing trunk,' and 'atypical bolero,' plus two extremity lesion patterns.

Conclusions:

• The 6B and 7B classification systems provide a useful framework for LCMNs.
• The 'hood' pattern for head and neck involvement and variations in other patterns warrant further investigation.
• Subclassifications may be needed to capture the full spectrum of LCMN distribution observed clinically.