Shave biopsies are increasingly being used in the diagnosis of invasive melanoma, including intermediate thickness tumours, raising concerns about adequate staging of the disease.

A study of 1,200 biopsies performed in Victoria in 2005, 2010 and 2015 showed a marked increase over time in use of shave biopsies as opposed to excisional biopsies.

Shave biopsies represented about 20% of all diagnostic biopsies in 2005; increasing to 36% in 2015. Excisional biopsies dropped from 78% to 62% during the same time period.

The increase was seen in thin melanomas (26% to 42%), intermediate thickness melanomas (16% to 38%) and thick melanomas (13% to 24%).

A number of tumours were subsequently T-upstaged – 12% overall – but more often with increasing thickness of the lesion.

The study, published in the MJA, found shave biopsies transected the tumour base in 54% of cases.

“Base transection is a particular problem when the tumour thickness is close to the 1 mm threshold for sentinel lymph node biopsy, thereby creating a dilemma for management and impeding the accuracy of further staging,” said the study authors from the Victorian Melanoma Service, Alfred Hospital.

“We also found that shave biopsy was increasingly used to diagnose intermediate thickness tumours, and that the base was transected in 75% of such cases.”

“As ongoing adjuvant treatment trials include patients with stage IIB and C tumours classified as T3b (2.01–4.0 mm with ulceration) or T4 (> 4.0mm), the 2.0 mm and 4.0 mm thickness cut-offs are critical for management decisions.”

“While inaccurate tumour microstaging may not have directly affected patient outcomes in the past, the choice of biopsy technique may influence patient outcomes in the era of effective adjuvant therapy.”

The study noted the increase in shave biopsies was seen in procedures performed by dermatologists and GPs but not by surgeons.

The researchers said the increasing use of the shave technique and high rates of margin involvement suggested adverse outcomes were likely to increase.

The technique may be suitable for cosmetic outcomes in difficult locations.

“Our data suggest that shave biopsy is increasingly used for assessing melanomas that do not meet these criteria or have clinical features associated with invasive melanoma, including elevation, induration, bleeding, ulceration, and dermoscopic features such as blue or grey colour, atypical vessels, white streaks, or regression features. We advocate excising such melanomas for the initial diagnosis.”