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Pathologists' diagnoses of some melanomas may not be accurate
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Pathologists had lower levels of accuracy and reproducibility in diagnosing moderate dysplastic nevus, melanoma in situ and early stage invasive melanoma, compared with benign nevi and high stage invasive melanoma, according to recently published study results in BMJ.
Researchers recruited 187 pathologists from 10 U.S. states who interpreted 240 skin biopsies, which were grouped into five sets of 36 or 48. The pathologists were randomized to independently interpret the same set of biopsy cases on two occasions at least 8 months apart.
The pathologists’ interpretations were placed in five classes, I-V, ranging from nevus or mild atypia to at least T1b invasive melanoma, and reproducibility was measured by intraobserver and interobserver concordance rates. Concordance with three reference diagnoses was used to measure accuracy.
In the first phase of interpretations, the pathologists completed 8,976 independent case interpretations for an average of 10 different diagnostic terms for each case.
“Among pathologists interpreting the same cases in both phases, when pathologists diagnosed a case as class I or class V during phase 1, they gave the same diagnosis in phase 2 of the majority of the cases (class I, 76.7%; class V, 82.6%),” the researchers wrote. “However, the intraobserver reproducibility was lower for cases interpreted as class II (35.2%), class III (59.5%) and class IV (63.2%).”
Although the interobserver concordance rates were lower, they had similar trends.
When consensus diagnosis of experienced pathologists was used a reference, accuracy varied by class, including 92% (95% CI, 90-94) for class 1, 25% (95% CI, 22-28) for class II, 40% (95% CI, 37-44) for class III, 43% (95% CI, 39-46) for class IV and 72% (95% CI, 69-75) for class V.
“It is estimated that a population level, 82.8% would of melanocytic skin biopsy diagnoses would have their diagnosis verified if reviewed by a consensus reference panel of experience pathologists, with 8% of cases overinterpreted by the initial pathologists and 9.2% underinterpreted,” the researchers wrote.
The researchers noted that class 1 benign nevi and class V high stage invasive melanoma, which are at opposite ends of the histopathologic spectrum, received the most accurate diagnoses, while the cases in the middle of the spectrum had lower accuracy.
“This study highlights challenges and limitations in the diagnosis of melanocytic skin lesions by current practicing pathologists,” the researchers wrote. “Efforts to improve clinical practice should include simplification of terminology by use of a standardized classification system, acknowledgement of the extant uncertainty of specific diagnoses in pathology reports, and development of more sophisticated diagnostic tools to support pathologists.” – by Bruce Thiel
Disclosure: All researchers report receiving financial support from the National Cancer Institute for the submitted work. Please see the full study for individual researchers’ relevant financial disclosures.
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