Mohs Paste Should Not Be Discounted for Treating Melanoma

"Mohs paste is a tried and true compound that does what it’s purported to do."

"The first patient I [used the paste on] developed a sentinel node that was swollen and large, and I thought it was a metastatic, but it turned out to be clearly an immune response. On the flip side – I don’t paste everyone. But if I have a high-risk patient who is well balanced and capable of understanding the implications, I do offer to paste them."

It is important to get informed consent and explain that zinc chloride is not an approved therapy; however, assure the patient it will not interfere with any other therapy they might want to pursue. Consider reserving it for high-risk patients, many of whom have melanoma that extends to the bone. "If you do your Mohs down to the periosteum and want to know if the bone is clear, you can paste it and a day or so later the bone will decalcify and a little chip will come out and you can examine that."

Mohs paste has fallen out of use over the years as fresh-tissue surgery has gained popularity. "Fresh-tissue replaced it because it allows immediate closure, while the paste causes a lot of inflammation and, the way Dr. Mohs did it, it left a wound that healed by secondary intention. It heals well but people won’t stand for that these days." Younger physicians, he said, "want to use what’s new, and what they were taught to use."

For many years, Dr. Mohs got the paste from just one pharmacist, who retired long ago. "Then there was just no reliable place to get the stuff. But recently we’ve been able to work with Delasco, [a medical supply company] that can compound it very reliably. It’s cheap and a small amount will last virtually forever at room temperature."

Because Mohs paste is composed of natural ingredients and has been in use for so long, it is an unpatentable therapy. Therefore, it will probably always remain on the fringes of medicine.

"You will never find any large head-to-head studies with other therapies, and no pharmaceutical company is ever going to research it. It would cost millions of dollars to do the kind of studies you’d need to get approval and then what would you have at the end? Nothing you could make money off of. So it won’t happen."

Aside from some slight discomfort and the inflammatory reaction, however, there are few down sides to using the paste. "If you look at it from a perspective of what can I do that won’t hurt my patients, probably helps them, and won’t interfere with definitive, modern therapy, I would say Mohs paste is a shining example."

Kenneth Gross, M.D., was a course director at the meeting, and is a surgical dermatologist in San Diego. He reported having no relevant conflicts of interest.