Pathology Wisdom for APPs: Lessons in Avoiding Common Diagnostic Challenges

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At the 2024 Elevate-Derm West Conference, held in Scottsdale, Arizona, Whitney High, MD, delivered an informative session titled “Pathology Pearls and Pitfalls for the Experienced APP.”¹ High, director of dermatopathology at the University of Colorado Anschutz Medical Campus, tailored his presentation to equip experienced advanced practice providers (APPs) with insights and cautionary advice critical for dermatopathology practice.

Bridging Dermatology and Dermatopathology: A Career in Both Fields

With extensive experience leading both dermatology and dermatopathology departments, High emphasized the importance of understanding the intersection between the 2 fields, where many diagnostic and clinical challenges arise.

"Very often, when there’s a problem in medical misadventures, they say, it involves dermatology and dermatopathology," High noted.

Understanding the Dermatopathology Pathway

High explained the 2 main pathways into dermatopathology: dermatology and general pathology. Dermatologists transitioning into dermatopathology often bring a clinic-focused perspective, while those with a pathology background may lean more toward a laboratory-driven approach. The key takeaway was that understanding how dermatopathologists reach their diagnoses can make APPs more effective "consumers" of dermatopathology services.

"In teaching you more about dermatopathology, you can be a better consumer of dermatopathology services and understand a little bit about how the diagnosis is made, so that you can get better results for the patient. It's important to understand the general practice of dermatopathology," High said.

Behind the Scenes of a Dermatopathology Lab

Taking attendees on a journey from clinic to lab, High illustrated the intricate process that a biopsy specimen undergoes. From proper biopsy technique to neutral-buffered formalin fixation, every step in the lab process is crucial for accurate diagnosis. He called this the "chain of dependency," explaining that errors could occur at any stage—from specimen collection to processing.

"It’s really, really important that you’re aware that it’s a process fraught with potential for error," High emphasized. "There’s mantras in pathology: Crap in equals crap out. If you put a crappy biopsy into the specimen, you get a crappy result. If you put crappy information on your form, you get crappy information on your pathology report."

Ensuring Accuracy: Minimizing Potential for Misidentification

A crucial part of High’s presentation focused on the risks of misidentification. He highlighted a national survey revealing a misidentification rate of 4per 1,000 specimens across all pathology fields. With dermatology providers typically handling around 2,500 biopsies annually, this statistic translates to approximately 8 misidentified cases per year. To mitigate this, High’s lab employs a color-coded ink system to ensure specimen traceability and prevent errors—a practice not widely adopted due to its labor-intensive nature, but one that adds an extra layer of security.

Navigating Complex Biopsy Decisions in Dermatology

In a related discussion on clinical decision-making, High provided additional insights into managing challenging biopsy decisions. The conversation touched on the nuances of biopsy selection, patient care, and the potential for misdiagnosis. One particularly important lesson was the need for flexibility and individualized care in biopsy decisions. High warned against rigid rules, such as the idea that the "thickest part" of a lesion should always be biopsied. While this may be a helpful general guideline, he pointed out that melanoma and other atypical lesions may require a more nuanced approach.

"You want to have some latitude to make these kinds of clinical decisions," High said. "Whether you're an MD or not an MD or anything else, we're all providers that are making important healthcare decisions."

Limitations of Traditional Biopsy Methods

Punch biopsies, while commonly performed, were also a topic of discussion. High shared findings from a 2010 JAMA Dermatology study² that showed punch biopsies have a 17-fold higher risk of misdiagnosis compared to excisional biopsies. Despite their risks, punch biopsies remain an essential tool, particularly when excisional biopsies are impractical. In these cases, High recommended referring patients with large or concerning lesions to specialists for more definitive procedures when necessary.

High also acknowledged that traditional biopsy methods—especially punch and shave biopsies—have inherent limitations. These techniques often provide only a small sample of tissue, which can be insufficient for accurate diagnosis. This is particularly problematic for pigmented lesions, where key information about the lesion’s depth or lateral extension might be missed.

Special Considerations: Varus Carcinoma and Mycosis Fungoides

High also highlighted specific conditions, such as varus carcinoma and mycosis fungoides, which require particular attention when biopsying. Varus carcinoma, which is associated with large, deep warts, often goes undiagnosed due to insufficient tissue sampling. Similarly, mycosis fungoides can be mistaken for eczema in its early stages, requiring multiple biopsies and a careful clinical-pathological correlation to reach a definitive diagnosis.

The Art of Clinical Decision-Making

In conclusion, High reinforced the need for a balanced, flexible approach to clinical decision-making. Biopsy methods, while essential, have their limitations and must be used judiciously. Successful dermatopathology depends on a provider’s ability to make informed, individualized decisions—keeping in mind the full clinical context and avoiding the trap of one-size-fits-all rules. By maintaining a high standard of clinical expertise and communication, dermatology providers can navigate the complexities of biopsy decisions and deliver the best care for their patients.

References

1. High W. Pathology pearls and pitfalls for the experienced APP. Session presented at: Elevate-Derm West Conference; November 7-10; Scottsdale, Arizona.
2. Ng JC, Swain S, Dowling JP, Wolfe R, Simpson P, Kelly JW. The impact of partial biopsy on histopathologic diagnosis of cutaneous melanoma: experience of an Australian tertiary referral service. Arch Dermatol. 2010;146(3):234–239. doi:10.1001/archdermatol.2010.14

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