Case Study: The Atypical Seborrheic Keratosis That Almost Got Biopsied

The Challenging Presentation

When Mrs. Johnson, a 62-year-old retired teacher, came to our clinic for her annual skin check, one particular lesion immediately caught my attention. Located on her upper back was a dark brown growth with irregular borders and varying shades of pigment. At first glance, the lesion displayed several concerning features that made my experienced eye pause. The patient herself had noticed this spot changing over several months, describing it as becoming darker and slightly larger. In standard visual examination under bright lighting, the lesion measured approximately 8mm in diameter and presented with what we call the "ugly duckling" sign – it looked distinctly different from her other numerous benign moles and skin growths. The clinical presentation was sufficiently worrisome that I found myself mentally preparing the patient for the possibility of needing a biopsy to rule out melanoma, the most dangerous form of skin cancer.

The Initial Dermoscopic Examination

I began my detailed assessment using polarized dermoscopy, a technique that allows us to view subsurface skin structures without direct contact with the lesion. The polarized light revealed some intriguing patterns but left me with more questions than answers. I could observe what appeared to be blue-gray areas that sometimes indicate regression in melanomas, along with some whitish streaks that could represent regression or fibrosis. The polarized view also showed some vessel structures, but they appeared somewhat blurred and non-specific. This is where understanding the nuances between polarized vs non polarized dermoscopy becomes crucial in clinical practice. While polarized dermoscopy excels at revealing deeper structures and doesn't require contact with the skin, it can sometimes miss subtle surface features that become apparent only with direct contact and fluid application. The challenging nature of this case under polarized light reinforced why having multiple diagnostic tools at our disposal is essential for accurate skin cancer detection.

The Turning Point: Switching Techniques

Recognizing the limitations of the initial examination, I made the decision to switch to non-polarized contact dermoscopy with the application of a clear fluid interface. This technique requires direct contact between the dermatoscope and the skin, with a fluid such as alcohol or ultrasound gel eliminating surface reflection. The transformation in what I could see was remarkable. Suddenly, features that were ambiguous became much clearer. The milky-like keratin pseudocysts and comedo-like openings characteristic of seborrheic keratosis emerged with distinct clarity. Most importantly, I began to identify the specific vascular patterns that would become the diagnostic key to this case. This comparison between polarized vs non polarized dermoscopy demonstrates why experienced dermatologists often use both modalities complementarily, especially when dealing with diagnostically challenging lesions.

The Diagnostic Clue: Recognizing Characteristic Vessels

As I carefully scanned the lesion with the non-polarized contact dermoscopy, my attention was drawn to focal areas displaying what experienced dermatologists recognize as classic seborrheic keratosis dermoscopy vessels. These appeared as delicate, hairpin-like vessels with surrounding whitish halos, along with some twisted looped vessels that are quite characteristic of this benign condition. The vessels were not uniformly distributed throughout the lesion but appeared in clusters, which is typical for seborrheic keratoses. The identification of these specific seborrheic keratosis dermoscopy vessels provided the crucial diagnostic clue that had been missing in the initial polarized examination. These vascular patterns, when combined with the other classic features now visible, painted a clear picture of a benign seborrheic keratosis rather than a malignant melanoma.

Corroborating Evidence with Additional Technology

To further support my diagnosis and provide additional reassurance to both myself and the patient, I employed a portable Woods Lamp to examine the lesion. The portable Woods Lamp emits ultraviolet light that causes certain skin substances to fluoresce, providing another dimension of diagnostic information. Under the Wood's light examination, the lesion showed the typical faint, non-specific fluorescence of a seborrheic keratosis rather than the complete absence of fluorescence (black) sometimes seen in heavily pigmented melanomas. While the portable Woods Lamp alone wouldn't have been diagnostic in this challenging case, it served as valuable supporting evidence that reinforced the diagnosis suggested by the dermoscopic findings. The combination of multiple examination techniques – both polarized and non-polarized dermoscopy along with Wood's light examination – created a comprehensive diagnostic picture that gave me confidence in my assessment.

Preventing an Unnecessary Procedure

The correct identification of this lesion as a benign seborrheic keratosis rather than a potentially deadly melanoma prevented what would have been an unnecessary surgical biopsy. For Mrs. Johnson, this meant avoiding a procedure that would have left a scar, required healing time, and generated significant anxiety while waiting for pathology results. From a healthcare system perspective, it represented appropriate resource utilization and cost savings. This case powerfully illustrates how mastery of different diagnostic techniques, including both polarized vs non polarized dermoscopy and supplemental tools like the portable Woods Lamp, directly impacts patient care and outcomes. The ability to recognize specific features such as seborrheic keratosis dermoscopy vessels can make the difference between an unnecessary surgical procedure and appropriate conservative management.

Clinical Pearls and Takeaway Lessons

This case offers several valuable lessons for dermatology practitioners. First, it underscores the importance of being proficient with both polarized and non-polarized dermoscopy techniques, as they reveal complementary aspects of skin lesions. Second, it highlights the diagnostic value of carefully examining vascular patterns in challenging lesions, with specific attention to recognizing seborrheic keratosis dermoscopy vessels. Third, it demonstrates how supplemental tools like the portable Woods Lamp can provide additional diagnostic confidence in borderline cases. Finally, it reminds us that even classically benign entities like seborrheic keratosis can sometimes present in alarming ways that mimic melanoma, requiring thorough evaluation before determining the appropriate management path. These clinical pearls, born from direct experience with challenging cases, contribute to the ongoing development of diagnostic expertise in dermatology.