Beyond Melanoma: Utilizing Dermoscopy for the Diagnosis of Other Dermal Nevi Variants

I. Introduction: Dermoscopy Beyond Melanoma Screening

For decades, the primary and most celebrated role of dermoscopy in clinical dermatology has been its unparalleled ability to improve the early detection of melanoma, thereby saving lives. However, to view dermoscopy solely as a melanoma-screening tool is to vastly underutilize its potential. The technique, which allows for the non-invasive, in vivo visualization of subsurface skin structures in the epidermis, dermo-epidermal junction, and papillary dermis, is equally transformative for the diagnosis and management of a wide spectrum of benign and malignant lesions. This article focuses on expanding this role into the nuanced realm of dermal nevi variants. These are melanocytic nevi where the nest of nevus cells is primarily located within the dermis. While often clinically benign, certain variants can present with alarming features that closely mimic melanoma, leading to unnecessary surgical excisions and patient anxiety. The dermoscopy examination provides a critical bridge between gross clinical inspection and histopathology, offering a detailed morphological roadmap.

Common dermal nevi variants, such as Spitz nevi, Reed nevi, blue nevi, and halo nevi, each pose unique diagnostic challenges. Clinically, a Spitz nevus may appear as a rapidly growing, pink or pigmented nodule in a child, raising immediate concern. A Reed nevus can present as a jet-black, irregularly bordered macule, indistinguishable from early melanoma to the naked eye. Herein lies the immense value of dermal nevi dermoscopy. By revealing specific architectural patterns and color distributions not visible to the unaided eye, dermoscopy significantly improves diagnostic accuracy. It allows dermatologists to move beyond a binary "suspicious or not" mindset towards a more refined, pattern-based diagnosis. In a busy Hong Kong dermatology clinic, where a 2022 audit from the Hong Kong Dermatological Society noted that pigmented lesions constitute over 30% of outpatient consultations, mastering the dermoscopic signatures of these variants is not an academic exercise but a clinical necessity to optimize patient care and resource allocation.

II. Dermoscopic Features of Specific Dermal Nevi Variants

A. Spitz Nevus

The Spitz nevus, historically termed a "juvenile melanoma" due to its histological similarities, is a classic example where dermoscopy is indispensable. The archetypal dermoscopic pattern is the starburst pattern, characterized by prominent, regularly distributed radial streaks or pseudopods at the entire periphery of the lesion. These streaks are often dark brown or black and converge symmetrically. Other classic patterns include the globular pattern (multiple, tightly packed brown globules) and the homogeneous pattern (a structureless, pink or light-brown area). A pink Spitz nevus may show dotted or comma vessels over a milky-red background. The critical application is in differentiating it from melanoma in children and young adults. While melanoma in this age group is rare, it does occur. Asymmetry, atypical streaks that are not uniform, and the presence of blue-white structures over regression areas are more concerning features favoring melanoma. A thorough dermoscopy procedure for a suspected Spitz lesion involves careful evaluation of symmetry, color uniformity, and the regularity of peripheral structures.

B. Reed Nevus (Pigmented Spindle Cell Nevus)

Reed nevi are typically darkly pigmented, flat or slightly raised lesions, most common on the limbs of young women. Dermoscopically, they are renowned for their striking homogeneous blue-black pigmentation, which may appear as a solid, structureless, dark blue to black blot. A common variant is the "peripheral globular" type, where the center is blue-black and the periphery is surrounded by a rim of brown globules. The primary challenge is distinguishing it from melanoma, especially nodular melanoma, which can also present with homogeneous blue-black color. Key reassuring features for a Reed nevus include its symmetry, sharp demarcation, and the classic "starburst" pattern (similar to Spitz), where dark, radial streaks are seen at the periphery. The absence of multiple colors (e.g., red, white, blue-gray), ulceration, or polymorphous vessels supports a benign diagnosis. However, any deviation from this classic picture warrants extreme caution and often excision.

C. Blue Nevus

The diagnosis of a blue nevus is one of the most straightforward for dermoscopists, thanks to its pathognomonic pattern. The classic dermoscopic finding is a homogeneous blue pattern—a structureless, steel-blue to blue-gray pigmentation that is uniform throughout the lesion. This blue hue is caused by the Tyndall effect, where light scatters as it passes through the collagen overlying deeply dermal melanocytes. Common blue nevi are typically smaller (

D. Halo Nevus

A halo nevus is characterized clinically by a central pigmented nevus surrounded by a symmetrical zone of depigmentation (the halo). Dermoscopy dramatically enhances the evaluation of both components. The central nevus can be of any type (e.g., compound, dermal) and is assessed for its own benign dermoscopic features. The surrounding halo appears as a structureless, white area with a well-defined inner border and a fading outer border. Critically, dermoscopy allows for the assessment of the regression features. In a benign halo nevus, the white area is pure and lacks the blue-gray peppering (fine blue-gray dots) that is often associated with regression in melanoma. The presence of such blue-gray granules within the halo, asymmetry of the halo itself, or atypical features in the central component should raise suspicion for a regressing melanoma simulating a halo nevus. Thus, the dermoscopy examination provides crucial insights into the biological process at play.

III. Case Studies: Dermoscopic Diagnosis of Dermal Nevi Variants

A. Case 1: Diagnosing a Spitz Nevus with Dermoscopy

A 7-year-old boy presented with a 4-month history of a rapidly growing pinkish nodule on his cheek. The parents were highly anxious about melanoma. Clinical examination revealed a 6mm, dome-shaped, pink-red papule with a smooth surface. Dermoscopy under non-polarized light with interface fluid revealed a striking pattern: a symmetric lesion with a prominent "pink" homogeneous area in the center, surrounded by regularly distributed dotted vessels. Most notably, there was a peripheral rim of small, brown globules. This combination—symmetry, central homogeneous pink area with dotted vessels, and a peripheral globular rim—is highly characteristic of a non-pigmented Spitz nevus. The absence of ulceration, blue-white structures, or atypical vessels was reassuring. The lesion was monitored with serial digital dermoscopy over 6 months, showing stability, thus avoiding an unnecessary surgical procedure on a child's face. This case underscores how a systematic dermoscopy procedure can guide conservative management.

B. Case 2: Differentiating a Reed Nevus from Melanoma

A 25-year-old woman noticed a new, very dark spot on her thigh. Clinical inspection showed a 5mm, jet-black, asymmetrical macule with slightly irregular borders—features that triggered a high index of suspicion. Dermoscopy, however, told a different story. The lesion revealed a symmetric, sharply circumscribed structure with a central, homogeneous blue-black pigmentation. At the periphery, there were subtle, but regularly spaced, dark brown radial streaks, creating an incomplete starburst pattern. The color was monomorphic (only black/blue-black), and there were no red areas (ulceration), white scar-like areas, or blue-gray regression. These features are classic for a Reed nevus. Based on the definitive dermoscopic diagnosis, the patient was reassured, and the lesion was documented for follow-up. In Hong Kong, where public awareness of skin cancer is rising, such precise differentiation prevents patient distress and frees up surgical capacity for truly malignant lesions.

C. Case 3: Identifying a Blue Nevus with Dermoscopy

A 40-year-old man had a long-standing, bluish-gray macule on his dorsal hand. It had been present for over 15 years but he sought consultation due to recent minor trauma to the area. Clinical differentials included a blue nevus, tattoo, or vascular lesion. Dermoscopy immediately clarified the diagnosis. The lesion displayed a perfectly homogeneous, steel-blue pigmentation throughout its entire 4mm diameter. The color was uniform, with no other structures, networks, or dots. This is the textbook homogeneous blue pattern pathognomonic for a common blue nevus. The patient was counseled that this was a benign, congenital-type lesion with an extremely low risk of malignancy, and no further action was needed. This rapid, confident diagnosis, achievable in seconds with a dermoscopy examination, exemplifies the tool's efficiency in daily practice.

IV. Advanced Dermoscopic Techniques for Complex Cases

While standard dermoscopy is powerful, complex or ambiguous lesions may benefit from advanced techniques. A fundamental understanding of the mode of observation is crucial. Polarized dermoscopy (contact or non-contact) highlights structures based on how they reflect and polarize light. It excels at visualizing shiny white structures (e.g., chrysalis/crystalline structures seen in some Spitz nevi and melanomas), blue-white veil, and vascular patterns without the need for contact gel. Non-polarized (contact) dermoscopy requires interface fluid to eliminate surface glare and provides superior visualization of the epidermal pigment network and colors within the epidermis. Many experts advocate for a combined approach, using both modes to gather complementary information on a single lesion.

Furthermore, dermoscopy should not be used in isolation. It is most powerful when integrated into a holistic diagnostic workflow. For equivocal dermal nevi, sequential digital dermoscopic monitoring (SDDM) over 3-6 months can detect subtle changes indicative of malignancy. In vivo reflectance confocal microscopy (RCM) can provide cellular-level resolution, acting as a "virtual biopsy" to further characterize ambiguous dermal nests seen on dermoscopy. The integration of these tools is becoming the gold standard in tertiary referral centers. For instance, managing a large, changing cellular blue nevus might involve baseline dermoscopy and RCM, with scheduled digital monitoring, thereby avoiding excessive surgery while ensuring safety. This multi-modal approach represents the pinnacle of modern, non-invasive dermatologic diagnosis.

V. Enhancing the Diagnosis of Dermal Nevi with Dermoscopy

The effective use of dermal nevi dermoscopy is not a static skill but a journey of continuous learning and pattern recognition. Engaging with atlases, participating in interactive dermoscopy courses, and reviewing one's own cases with histopathological correlation are essential for honing expertise. The patterns described for Spitz, Reed, blue, and halo nevi form a foundational lexicon that clinicians must internalize. As experience grows, so does the ability to recognize subtle deviations that signal potential malignancy.

The future of dermoscopy in diagnosing diverse skin lesions is bright and increasingly technological. Artificial intelligence (AI) algorithms are being trained on vast libraries of dermoscopic images to assist in pattern recognition, potentially serving as a decision-support tool for less experienced clinicians. Teledermoscopy allows for expert consultation across geographical barriers, a feature particularly valuable for remote areas. The core principle, however, remains unchanged: dermoscopy provides a unique window into the living pathology of the skin. By mastering its use for dermal nevi and beyond, dermatologists can deliver more accurate diagnoses, reduce unnecessary procedures, improve patient outcomes, and ultimately, build a practice grounded in the highest standards of the E-E-A-T framework—Experience, Expertise, Authoritativeness, and Trustworthiness.