Making the High Cure Rate of Mohs More Worth it with Digital Pathology
Blog Posted: Feb. 4, 2020

Over one million new cases of non-melanoma skin cancers (NMSC) are diagnosed annually in the United States and the prevalence of skin cancer is five times higher than that of breast or prostate cancer. The incidence of NMSC is increasing worldwide, especially in the United States. Mohs surgery is the treatment of choice for certain NMSC primarily because the cure rate is 98%. Mohs high cure rate hinges upon the glaring inefficiency of Mohs: the frozen tissue evaluation. What if we made fresh tissue evaluation available to Mohs surgeons?

Let’s break down the inefficiencies that every Mohs surgeon complains about. Between each layer of skin removal the frozen section evaluation is the rate limiting step. Through our interactions, we have observed frozen section evaluations to be a hassle and inconsistent across many areas of pathology. The process of removing layers of skin is repeated until no cancer is detected in the tumor margin. Multiple excisions are often necessary to achieve cancer free margins, with the frozen section step often requiring 4–10 times the amount of time it takes to actually excise the tissue. What do patients do during this time? They wait. What do Mohs surgeons do during much of this time? If they are fortunate with resources, they watch TV, sometimes with the patient. Then they quickly check the margin. Our interactions included a harrowing day where multiple cases required 4 stages - taking longer than 8 hours. It’s an endless cycle of a bit of procedure for a lot of hassle and waiting. But at least the cure rate is very high - so let’s find a way to make that more worth it.

Enter digital pathology systems for fresh tissue scanning. That’s right - the tissue specimens don’t have to be cut and you don’t need a cryostat. No flash freezing, no embedding and no sectioning. A freshly excised layer is placed directly on a fresh tissue scanner and imaged at the microscopic resolution needed to make a margin evaluation. You wouldn’t even have to leave the bedside (unless you want to get to the next excision while your technician was quickly preparing the digital image to review upon return). Imagine excising a layer in 5 minutes and reviewing the digital image of it histologically within 5 minutes. Imagine only bouncing between 2 cases at the same time instead of 5 (we know a lot of you all do it). Since most Mohs cases do complete in 1-2 stages - imagine the majority of cases finishing within 30 minutes. By using digital pathology in Mohs, the valuable time of the pathologist and the patient will not be wasted - they can watch TV at home with their families (or treat more patients).

Of course the potential to treat more patients results in more revenue for Mohs centers. So, if fresh tissue scanners are validated as analogous to frozen sections (it’s happening), would adoption of digital pathology for Mohs be worth it? If you charge $1000 per Mohs surgery today and schedule 5 per day ($5000) - do the simple math and schedule 10 to make $10,000 per day in the same amount of time. What if digital pathology let you complete your entire caseload for the week in 1 day?

Fresh tissue scanners that permit examination of specimens will be hitting the market soon. Mohs margin evaluation is a compelling use case given these scanners provide the necessary resolution without having to cut, freeze, or otherwise destroy the tissue. Images can be analogous to H&E and delivered at the magnification relevant for Mohs margin evaluation. Spending less time cutting samples, delivering high quality images, and easing the training requirements makes the Mohs application feel like a slam dunk. We envision a world where digital pathology through fresh tissue scanners enables higher procedural throughput and revenue potential while maintaining the high cure rate of Mohs.

Built on the vision of better patient outcomes, Instapath was founded in 2017 by engineers and scientists to enable patients to immediately know their cancer diagnosis. Our team made it our mission to develop fast and easy digital pathology technology so diagnosis can be made in minutes instead of days. To learn more about Instapath and our technology, visit https://instapathbio.com/tech/ or contact us at info@instapathbio.com.

References

Bouzari N., Olbricht S. Histologic pitfalls in the Mohs technique. Dermatol Clin. 2011;29:261–272. ix.

Chen ELA, Srivastava D, Nijhawan RI. Mohs Micrographic Surgery: Development, Technique, and Applications in Cutaneous Malignancies. Semin Plast Surg. 2018;32(2):60–68.

Gareau DS, Jeon H, Nehal KS, Rajadhyaksha M. Rapid screening of cancer margins in tissue with multimodal confocal microscopy. J Surg Res. 2012;178(2):533–538.

Vajdi T, Eilers R, Jiang SIB. Clinical Characteristics of Non-Melanoma Skin Cancers Recurring within 5 years after Mohs Micrographic Surgery: Single Institution Retrospective Chart Review. J Clin Investig Dermatol. 2017;5(1):10.13188/2373-1044.1000036. doi:10.13188/2373-1044.1000036

David Tulman David Tulman, Ph.D. | Chief Clinical Officer at Instapath
Tags:  digital-pathology Mohs