Using p63 Immunohistochemistry during Mohs micrographic surgery for cutaneous squamous cell carcinoma

Skin cancer is a common challenge in modern medicine, and one of its most serious forms is cutaneous squamous cell carcinoma. This type of cancer arises from the flat cells that make up the outer layer of the skin. While many cases are straightforward to treat, some are aggressive and lack clear boundaries, making them difficult to remove completely. To address this, surgeons often use a specialized technique called Mohs micrographic surgery. This method involves removing the cancer layer by layer and immediately examining each piece under a microscope to ensure no cancer cells remain. The goal is to save as much healthy tissue as possible while guaranteeing the tumor is gone. However, when the cancer cells are poorly differentiated—meaning they look very different from normal skin cells and lack distinct features—they can be nearly invisible to the naked eye during a standard microscope exam. This is where new tools become essential, offering a way to highlight the invisible and guide the surgeon's hand with greater precision.

Researchers at the University of Rochester recently explored a specific tool to solve this visibility problem. They focused on a staining technique that uses a protein marker called p63. In the laboratory, doctors use special dyes to make certain cells light up under a microscope, much like turning on a flashlight in a dark room to see what is there. The standard dye used for this purpose is known as AE1/AE3, which highlights the structural proteins found in skin cells. While effective, this standard dye has a drawback: it also lights up healthy skin structures, such as sweat glands and hair follicles, often very brightly. This can create visual clutter, making it harder for the surgeon to distinguish between the healthy tissue and the cancer. The team investigated whether switching to or adding the p63 stain could provide a clearer picture, as this marker is known to be very active in squamous cell carcinoma but less active in the surrounding healthy skin structures.

To test this idea, the team treated sixteen patients with poorly differentiated squamous cell carcinoma using this new staining approach during their surgery. They applied the p63 stain to the tissue samples removed from the patients, sometimes using it alone and other times alongside the standard AE1/AE3 dye. The surgeons and pathologists then examined the slides to see how well each stain worked. They looked for two things: how brightly the cancer cells lit up and whether the healthy skin structures were also lighting up, which would cause confusion. The results showed a distinct difference between the two methods. The standard AE1/AE3 stain caused the healthy sweat glands and hair follicles to glow intensely, creating a background that could distract from the tumor. In contrast, the p63 stain left these healthy structures almost completely dark, providing a clean, high-contrast view of the cancer cells.

The data revealed that the p63 stain was particularly good at highlighting the cancer. In nearly nine out of ten cases where the stain was used, the tumor cells showed a strong, clear reaction. By comparison, the standard stain highlighted the cancer cells strongly in only about six out of ten cases. In three specific instances, the standard stain failed to show the tumor cells at all, while the p63 stain made them clearly visible. This suggests that relying solely on the older method might occasionally leave cancer behind because it simply cannot be seen. The researchers also noted that in one case, the standard stain highlighted fragments of keratin, a skin protein, that were not part of a tumor, which could have been mistaken for cancer. The p63 stain avoided this confusion entirely.

The study followed these patients for an average of twelve months to see how they fared after the surgery. During this time, two patients experienced a return of the cancer at the original site, and two patients passed away. However, the researchers confirmed that the deaths were due to causes unrelated to the skin cancer. The two recurrences happened in cases where both stains were used, indicating that while the new stain improves visibility, it is not a guarantee against all future issues. The authors conclude that using the p63 stain during surgery offers a significant advantage by making the cancer stand out more clearly against the healthy tissue. It does not replace the standard method but works better when used together, helping surgeons identify difficult-to-see tumors that might otherwise be missed. While more research with larger groups of patients is needed to confirm these findings, this approach shows great promise for improving the accuracy of skin cancer removal.