Linear Cowden nevus: a new distinct epidermal nevus

Area of Science:

• Dermatology
• Clinical Genetics
• Pathology

Background:

• Epidermal nevi encompass a range of congenital skin conditions.
• Cowden disease is a genetic disorder associated with PTEN gene mutations.
• Distinguishing between similar-appearing nevi is crucial for accurate diagnosis and management.

Purpose of the Study:

• To define and characterize a specific type of epidermal nevus termed "linear Cowden nevus".
• To differentiate linear Cowden nevus from Proteus syndrome.
• To establish linear Cowden nevus as a distinct clinicogenetic entity.

Main Methods:

• Clinical observation and comparison of epidermal nevi.
• Genetic analysis to identify PTEN mutations.
• Histopathological examination of nevus characteristics.

Main Results:

• Linear Cowden nevus is identified as a non-organoid epidermal nevus resulting from early embryonic loss of heterozygosity in individuals with germline PTEN mutations.
• This condition is classified as a manifestation of type 2 segmental Cowden disease.
• Clinical distinctions include the papillomatous and thick nature of linear Cowden nevus compared to the flatter linear Proteus nevus.
• Associated cutaneous and extracutaneous anomalies differ between the two conditions.
• Proteus syndrome is confirmed not to be caused by PTEN mutations.

Conclusions:

• Linear Cowden nevus, also termed "linear PTEN nevus", is a distinct clinicogenetic entity.
• Accurate differentiation from Proteus syndrome is essential for correct diagnosis.
• Understanding the genetic basis (PTEN mutations) clarifies the classification of linear Cowden nevus within Cowden disease spectrum.