Melanomas misdiagnosed with increasing use of shaved biopsies

By Sunalie Silva

2 Sep 2021

Partial shave biopsy has been linked to an increased risk of both false-negative and false-positive melanoma diagnosis resulting in several cases of disease progression following delayed diagnosis, a large Melbourne study finds.

Specialists from the Victorian Melanoma Service (VMS) at the Alfred Hospital involved in the study warn that the risk of misdiagnosis associated with the increasingly popular technique was found to be comparable with incisional punch biopsy and significantly higher than complete elliptical excisions biopsy.

Dr Yonatan Kok and colleagues say the use of shave biopsy has been steadily growing with widespread acceptance of  the approach in recent years as a relatively quick and inexpensive method of sampling melanocytes lesions

Writing in the Australasian Journal of Dermatology, the group said their own institution reported on the significant risk of false negative melanoma diagnosis for incisional punch biopsy when compared with complete elliptical excisional biopsies a decade ago, which they say may have contributed in part to the decline in its use over the last five years and a shift in clinician’s preference towards shave biopsy.

Comparing rates of biopsy techniques use between 2014–2016 and 2017–2019, the proportion of partial biopsies increased from 41.9% to 44.6% with an increase in partial shave biopsies by 5.1% and a decrease in incisional punch biopsies by 2.9%.

That finding prompted their current review into the misdiagnosis rates associated with the technique that’s fast been replacing others.

In an analysis of 3668 referrals to the VMS between January 2014 and 31 May 2019, 80 (2.2%) had a false-negative diagnosis and 232 (6.3%) had a false-positive diagnosis.

Significantly, almost half of the patients with melanoma progression following false-negative diagnosis in this study had an initial partial shave biopsy.

Complete elliptical excisions formed the majority of biopsies performed (2037 cases, 55.5%), followed by partial shave biopsies (1013 cases, 27.6%) and incisional punch biopsies (474 cases, 12.9%).

Over 40% of false negative cases were invasive melanoma at the time of definitive diagnosis and 27.3% of these cases developed metastatic disease.The mean time from the initial false-negative diagnosis to the definitive diagnosis of melanoma was 25.2 months (95% CI 18.7–31.7) with a mean increase in Breslow thickness of 0.59mm (95% CI 0.25–0.93).

Two year delay

“Although we cannot be certain that a correct diagnosis at the initial presentation would have prevented melanoma metastasis, the mean delay of more than 2 years before lesions were resampled to reach a correct diagnosis is concerning,” they said of the finding.

According to investigators, false-negative cases were more likely to affect females (53.7%), to involve the head and neck (45.0%) and to be of superficial spreading subtype (37.5%).

The most common initial biopsy technique associated with melanoma progression following a false-negative diagnosis was partial shave biopsy (47.6%), followed by complete elliptical excision (28.6%), incisional punch biopsy (19.0%) and partial curette (4.8%).

Meanwhile there were 232 cases of false-positive diagnoses. Benign lesions were most often incorrectly diagnosed as superficial spreading (48.7%) and in situ melanoma (84.5%). A total of 18 benign cases (7.7%) were initially identified as naevoid, Spitzoid, desmoplastic or acral lentiginous melanoma.

Both partial shave (OR 1.95, 95% CI 1.45–2.63; P < 0.001) and incisional punch biopsy (OR 2.00, 95% CI 1.37–2.90; P < 0.001) increased the odds of false-positive diagnosis when compared with complete elliptical excisional biopsy.

But the group also reported that documentation of the suspected clinical diagnosis on pathology request forms and providing other clinical data significantly reduced the odds of misdiagnosis.

According to the team, detailing the anatomical site, suspected clinical diagnosis, specimen type, history of lesional trauma and past history of melanoma on pathology requisition forms appeared to assist pathologists reach an accurate final diagnosis. In the case of reducing the risk of a false-negative diagnosis with melanoma progression including the details improved odds by 3.8-fold (P = 0.02). They said that the information should be provided as a minimum.

The findings have prompted the dermatologists to urge clinicians to ‘carefully consider which lesions are suitable for shave biopsy  and follow guideline recommendations for complete excisional biopsy wherever possible’.

‘When a partial biopsy technique is chosen, the findings of this study should lead clinicians to consider questioning the histological assessment if it does not accord with clinical findings and to fully excise the lesion for diagnosis if there is any doubt,’ they concluded.

The study is published in the Australasian Journal of Dermatology.


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