Four questions regarding subungual melanoma

One of my toe nails (big toe) has a small spot under it (probably about 3 mm or so, fairly circular to the naked eye)...it's not what I'd refer to as a "streak," as it doesn't start at the base of the nail (it's upward and next to/bordering the lateral nail fold) and it doesn't go all the way to the end/distal part of the nail. I don't know exactly what color to call it...maybe a greenish-tan...at least under direct light.

However, there is some of that same "pigment" (if that's what it is) on the lateral nail fold. When I first discovered it I thought I may have seen a slight amount, but thought I might have just been nitpicking. But last Saturday I woke up and it was now visually obvious that it had spread to the lateral nail fold. Seemed to happen pretty much overnight, though it was a week and a half or so since I first noticed the mark.

So my questions are:

1. Does Hutchinson's sign refer only to longitudinal melanonychia that has spread to the proximal or lateral nail fold, or just any skin pigment/coloration in general?

2. Seems like a dumb question, but is it possible for the lateral nail fold (s) to bruise?

3. Do subungual melanomas always arise from the base of the nail?

4. And finally, does what I have seem like something I should be really concerned about?

Thanks in advance.

[Jasmina Jankicevic, MD, MSc, CCRP]

Welcome to the Dermatology Expert Forum! Thank you for your post with four excellent  questions.

Here are our answers:

1. Hutchinson's sign is a periungual extension of brown-black pigmentation from longitudinal melanonychia onto the proximal and/or lateral nailfolds.  It is an important indicator of subungual melanoma. However, periungual pigmentation is present in a variety of benign disorders (for example, dark greenish nail color you mentioned could be caused by pseudomonas bacteria). Ultimately, the diagnosis of subungual melanoma is excluded histologically.

2. Yes, it is.

3. Yes, most common sign is that longitudal melanonychia.

4. Do not be concerned, just be proactive. Based on your intelligent, focused questions, I see that you are well-informed on the matter, so you know that your condition needs to be evaluated by a dermatologist as soon as possible. Do not wait!


Wishing You Optimal Health,
Dr. Jasmina Jankicevic

[StillTrying49]

Had a dermatologist look at it and they told me it was fungus (onychomycosis). Should I trust that diagnosis, given how often SM is misdiagnosed?

For clarification--you're saying Hutchinson's sign is only present when longitudinal melanonychia is present? If it's just a rounded spot/non-streak that doesn't arise at the proximal part of the nail, even if there is some sort of pigment on one of the nail folds, it is technically not defined as "Hutchinson's sign?"

The reason I ask this is the spot on my toe isn't a line/steak. I just want to get a sense for whether or not I should push for a biopsy based on how the disease works. It would seem, based on the information provided, that this would be an unusual presentation for subungual melanoma. But then information can be misleading.

[Jasmina Jankicevic, MD, MSc, CCRP]

Hello, StillTrying49!

Diagnosis of onychomycosis should be conformed with laboratory diagnostic tests in addition to clinical examination.

Yes, you understood definition of HS properly. Description you provided sounds more like lesion caused by physical injury/trauma. However, whenever melanoma is mentioned as possible differential diagnosis, that should be thoroughly investigated. In such a case, biopsy is justified.

Wishing You Optimal Health,
Dr. Jasmina Jankicevic

[StillTrying49]

As an update, since beginning the treatment (thymol 4%) the spot has changed color...less noticeable than before (a reddish color that somewhat blends in), but the shape is also less circular. The lateral nail fold where I'd noticed the pigment is now thickened and peeling. I don't really know what to make of this.