Abstract:

In patients with newly diagnosed primary cutaneous melanomas, Breslow thickness (BT) or depth of invasion offers an important staging information and serves as one of the best independent predictors of patient outcome. Variations in depth measurement even by 0.1mm could impact an accurate ‘T’ stage assessment and pathologists traditionally measure BT microscopically with an ocular or stage micrometer. We sought to determine whether measurement of BT digitally using whole slide image (WSI) tool provide accurate and/or significant alterations in T’ staging when compared to manual method. Cases of primary cutaneous melanomas (N=145) reported at our institution from July 2020- January 2022 were scanned and converted to WSI at 0.25 ?M/pixel using an Aperio AT2 DX System. BT was remeasured digitally on WSI using the eSlide Manager tool and compared to manually measured and reported BT. Of the 145 cases, 67 (44%) showed concordant BT measurements and 78 (54%) cases demonstrated discordant results. Among these cases, BT differences ranged from 0.1mm to 1.3 mm, with median & mode being 0.1mm. Cases with BT differences of 0.1mm (n=49, 63%), 0.2mm (n=12, 15%) and 0.3 mm (n=6, 8%) were the three most common occurrences. Larger deviations (>0.4mm, n=10, 13%) were noted mostly in cases with higher T stages (T3 or T4 diseases). Of the 78 discordant cases, 6 cases (8%) resulted in change in T stage with 4 cases being down-staged and 2 cases were upstaged with most differences arising from 0.1 or 0.2 mm differences at various T stage cut off values. BT is an important staging and prognostic parameter that is prone to over/under estimation with microscopic evaluation. Digital tools on WSI offer consistent and accurate estimation thereby improving appropriate staging especially in cases where BT falls around T-stage cut off values. Costs associated with whole slide imaging, i.e., validation and turnaround time are potential barriers until system wide adoption of digital slide imaging.

Financial Disclosure:
No current or relevant financial relationships exist.

Suraj Patel

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(Poster #381) Digital Measurement of Breslow Thickness in Malignant Melanoma