When it comes to evaluating skin specimens, immunohistochemical (IHC) stains have transformed the way dermatopathologists identify and characterize melanocytic lesions. Two of the most widely used melanocytic markers — SOX-10 and MART-1 (also called Melan-A or MELA) — each bring something unique to the diagnostic table. Knowing when and why to reach for one over the other can make a real difference in diagnostic confidence.
What Are SOX-10 and MART-1?
Both SOX-10 and MART-1/Melan-A are IHC stains that work by deploying antibodies that adhere to specific markers on melanocytes, allowing pathologists to identify and evaluate these cells within a tissue specimen.
- SOX-10 is a nuclear stain — meaning it highlights the cell nucleus specifically. It is a newer marker and has demonstrated exceptionally high sensitivity in melanocytic lesions, particularly those with a spindled morphology.
- MART-1 (Melan-A) is a cytoplasmic stain — it labels a larger portion of the cell, making the stain more visually prominent on low-power examination.
When to Use SOX-10
SOX-10 is the preferred stain when dealing with cytologically bland spindled cells in the dermis, particularly in cases where desmoplastic melanoma or other subtle spindled melanocytic lesions are on the differential.
Why? Because SOX-10’s nuclear staining pattern has been shown to have a much higher sensitivity in desmoplastic melanoma than MART-1. In these challenging cases, desmoplastic melanoma cells can be sparse and easy to overlook, and SOX-10’s precise nuclear labeling helps pathologists pick them out with greater confidence.
At StratumDx, we routinely add a SOX-10 stain in any case involving spindled, dermal melanocytic lesions — it’s a standard part of our approach to these diagnostically challenging specimens.
When MART-1 / Melan-A Is Still Valuable
MART-1 has been in use longer than SOX-10, and many dermatopathologists are highly experienced in interpreting its staining pattern. Because it is cytoplasmic, it labels more of the cell — which means on low-power microscopy, you get a broader, more gestalt-level view of the extent and distribution of a melanocytic lesion.
This can be particularly helpful when you want a quick, comprehensive sense of how far a lesion extends before moving to higher power. It’s also the stain many pathologists first trained on, making it a reliable reference point.
A Matter of Preference — and Expertise
Here’s the honest truth: both stains are excellent, and both will get you to the right diagnosis in the vast majority of cases. The choice between them often comes down to pathologist preference and the specific clinical question at hand.
As one of our dermatopathologists put it: “It’s almost like asking someone what color car they like — people have strong preferences one way or the other.” Some pathologists are drawn to the clean, punctate nuclear signal of SOX-10; others prefer the fuller cellular labeling of MART-1.
What matters most is consistent, expert interpretation — and having a team that knows when to deploy each stain strategically.
The StratumDx Approach
At StratumDx, our dermatopathology team stays current on the evolving evidence behind IHC markers like SOX-10 and MART-1. We use these stains thoughtfully and deliberately — not as a checkbox, but as a diagnostic tool — to ensure every specimen gets the level of scrutiny it deserves. In addition to the classic melanocytic workhorse MART1 and SOX10 stains, we also incorporate newer standards, such as PRAME. Over the past decade, PRAME has been investigated as a melanocytic market of atypia. We often use this stain in conjunction with SOX10 and MART1.
Whether it’s a subtle desmoplastic melanoma hiding in a background of scar tissue or a straightforward junctional nevus, we apply the right stain for the right case, every time.
Have questions about how we approach complex melanocytic lesions? Contact the StratumDx team — we’re here to support you and your patients.