Reflectance Confocal Microscopy Characteristics for Melanocytic Nevi

Moles—formally called melanocytic nevi—are one of the most common benign skin growths, affecting nearly everyone at some point. But diagnosing and classifying them often requires invasive biopsies, which many patients and doctors wish to avoid. Now, a study from Chinese dermatologists offers hope: a non-invasive imaging tool called reflectance confocal microscopy (RCM) can reliably identify distinct patterns in different types of moles, potentially reducing the need for unnecessary biopsies.

The research, led by Yan Jing from The First Affiliated Hospital of Anhui Medical University and Yong Cui from China-Japan Friendship Hospital, analyzed 158 melanocytic nevi samples (confirmed by pathology) alongside their RCM images. The team focused on three common mole types: junctional (melanocytes only in the epidermis, the skin’s outer layer), intradermal (only in the dermis, the deeper layer), and compound (both layers). Unusual nevi (like blue or Spitz nevi) and those on hands or feet were excluded to ensure focus on typical cases.

RCM works by emitting low-power near-infrared light (830 nanometers) to scan the skin. It captures high-resolution images of the epidermis and upper dermis—up to 200 micrometers deep—without cutting or numbing the skin. As previous research in the Journal of the American Academy of Dermatology notes, RCM’s strength lies in its ability to reveal cell and tissue structure in real time, making it a “quasi-histological” tool for non-invasive diagnosis.

The team’s key finding? Each mole type has a unique RCM signature:

Junctional nevi: Most showed “ringed” or “meshwork” structures—small, bright polygonal cells outlining the skin’s dermal papillae (tiny projections that anchor the epidermis to the dermis).
Intradermal nevi: Appeared as dense or sparse nests of large, bright cells, formed by melanocytes clumping in the dermis.
Compound nevi: Combined both patterns, reflecting their mix of epidermal and dermal melanocytes.

These patterns matched pathological findings almost perfectly, suggesting RCM could classify moles without biopsies. For patients, this means fewer invasive procedures; for doctors, it means faster, more precise diagnosis—especially for low-risk moles.

Why does this matter? Currently, mole classification relies on biopsy results, which take time and carry small risks (like scarring or infection). RCM offers a safer alternative. As the team notes, it could also help monitor mole changes over time or track treatment effectiveness—all without a needle.

But the study comes with caveats. The team emphasizes their RCM-based classification is “hypothetical” rather than definitive. More research is needed to confirm these patterns in larger, more diverse populations. Still, the results align with broader trends: medical imaging is transforming how dermatologists care for skin lesions. As research in Arch Dermatology shows, RCM correlates well with dermoscopy (another non-invasive tool) but adds deeper structural details—making it a valuable addition to the clinician’s toolkit.

The work was supported by grants from the Fundamental Research Funds for the Central Universities of China (No. 3332018182), the Milstein Medical Asian American Partnership Foundation (No. MMAAP2016023), and the Open Research Funding of China Skin Image Database (No. CSID-ORF-201918). The authors report no conflicts of interest.

For patients with moles, and the doctors who treat them, this study highlights a game-changing tool. RCM won’t replace biopsies for suspicious or fast-changing lesions—those still require pathological confirmation. But for routine mole checks, it could make care safer, faster, and more patient-friendly. As the team writes, the ultimate goal is to “use non-invasive and available means to identify and classify nevi”—and this research brings that goal one step closer.

The study was published in the Chinese Medical Journal in 2019. Citation: Jing Y, Shen CB, Xue K, Li CX, Shen X, Wang ZY, Xu F, Meng RS, Yu JB, Cui Y. Reflectance confocal microscopy characteristics for melanocytic nevi. Chin Med J 2019;132:2510–2511. doi.org/10.1097/CM9.0000000000000440

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