A proposed classification for follicular involvement by melanoma

Area of Science:

• Dermatopathology
• Oncology
• Dermatology

Background:

• Folliculotropism in melanoma is not well-defined.
• A standardized system for categorizing hair follicle involvement by melanoma is lacking.
• This study aims to establish a logical categorization system.

Purpose of the Study:

• To propose and validate a categorization system for melanoma involving hair follicles.
• To describe distinct patterns of follicular involvement by invasive melanoma and melanoma in situ (MIS).

Main Methods:

• A retrospective archive search was performed over 24 years.
• Cases mentioning "follicle," "follicular," "folliculotropic," or "folliculocentric" and melanoma were identified.
• Identified cases were analyzed for patterns of melanoma involvement within hair follicles.

Main Results:

• Ninety cases of melanoma with hair follicle involvement were identified.
• Three distinct invasive patterns were observed: primary follicular, folliculotropic, and invasive melanoma arising from MIS with follicular involvement.
• Melanoma in situ (MIS) showed lentiginous, nested, or combined patterns of follicular involvement.

Conclusions:

• A proposed categorization system includes three distinct patterns for invasive melanoma and three for MIS involvement of hair follicles.
• This system is valuable for logically categorizing hair follicle involvement by melanoma.
• Further validation may enhance clinical and research applications.