– Many dermatologists find melanonychia to be intimidating. The clinical features are ambiguous, and the prospect of doing a painful nail apparatus biopsy can be daunting for the inexperienced. As a result, the biopsy gets delayed and melanoma of the nail is often initially a missed diagnosis, not uncommonly for years, with devastating consequences.

Dr. Nathaniel Jellinek, a dermatologist in private practice in East Greenwich, R.I. Bruce Jancin/MDedge News

Dr. Nathaniel Jellinek

Here are five teaching points on melanonychia provided by nail disease expert and Mohs surgeon Nathaniel Jellinek, MD, at the Hawaii Dermatology Seminar provided by the Global Academy for Medical Education/Skin Disease Education Foundation.

Rule #1: Always look beyond the nail

When a light-skinned person presents with more than one nail with pigmentation, the likelihood that one of them is melanoma is much less than if there is only one nail with melanonychia, according to Dr. Jellinek, a dermatologist in private practice in East Greenwich, R.I.

Also, be sure to look at the skin and mucosa. Consider the medications the patients may be taking: For example, cyclophosphamide (Cytoxan) is notorious for causing nail changes as a side effect. A past medical history of lichen planus, carpal tunnel syndrome, Addison disease, or other conditions may explain the melanonychia.

Nathaniel Jellinek, MD

Melanonychia in Laugier-Hunziker syndrome

Laugier-Hunziker syndrome is a condition worth getting to know. It’s an acquired disorder characterized longitudinal melanonychia and other pigmentary changes, which may include diffuse hyperpigmentation of the orolabial mucosa, ocular pigment, and/or pigmented palmoplantar lesions. It’s said to be rare, but Dr. Jellinek disagrees.

“Learn this one if you don’t know it. I see a case about every 2 weeks. It’s not heritable and not associated with any other medical condition,” he said.

Rule #2: Your dermatoscope is great for nails

What Dr. Jellinek considers to be among the all-time best papers on the value of dermoscopy for nail pigmentation was authored by French investigators. They analyzed 148 consecutive cases of longitudinal melanonychia and concluded that the dermoscopic combination of a brown background coupled with irregular longitudinal lines in terms of color, spacing, diameter, and/or lack of parallelism strongly suggests melanoma. A micro-Hutchinson’s sign, while a rare finding, occurred only in melanoma, where it represented periungual spread of a radial growth phase malignancy (Arch Dermatol. 2002 Oct;138[10]:1327-33).

“I think nail dermoscopy is most helpful for subungual hemorrhage. I average one referral per week for hemorrhage under the nail. On dermoscopy it’s as if someone took paint and threw it at the nail. Purple to brown blood spots, with no background color. This should be a doorway diagnosis of hemorrhage,” Dr. Jellinek said.

Rule #3: Know when you don’t know

“This is really the key for me,” the dermatologist commented. “There are automatic cases for biopsy, and more commonly routine cases for reassurance. But the gray zone, when you know you don’t know, is the key decision making moment.”

When something just doesn’t feel right, there’s absolutely nothing wrong with getting a second opinion, he stressed.

“It’s worthwhile getting to know people whose opinions you trust. There’s a saying I like to teach our fellows: ‘Never worry alone.’ So if you’re worried about someone, listen to that inner voice. There’s no shame in getting a second opinion. It’s great! Patients are never upset, either. They feel really well taken care of,” he said.

Rule #4: Don’t wimp out when a biopsy is warranted

Many dermatologists hem and haw about doing a biopsy for a concerning lesion on the nail, when they wouldn’t hesitate to biopsy a similarly suspicious lesion on the face.

But it’s essential to biopsy the right area, he added. For longitudinal melanonychia, that’s the matrix. The nail plate is the wrong place; a biopsy obtained there will result in an inappropriate benign diagnosis.

Nathaniel Jellinek, MD

Melanonychia from matrix lentigo

“The starter set is to do a punch biopsy. This is your gateway drug to the world of nail surgery. Lots of dermatologists are intimidated by nail surgery, but if you can do any minor surgery, you can do a punch of the matrix. All it takes is a little practice. And if all you can do is punch biopsies, you’re good for your career. If you can do that, you’re golden. There are people who’ve just done punch biopsies for their whole career and they don’t miss melanomas,” he said.

Step one is to undermine the proximal nail fold using a pediatric elevator, which costs only about $30. “If you’re going to do a lot of nail surgery, they’re really helpful,” he said.

There’s no need at all to evulse the nail. Just make oblique incisions in the proximal nail fold in order to reflect it and look at the matrix. A 3-mm punch is standard, directed right over the origin of the pigment. Resist the temptation to force or squeeze the specimen in order to extract it. Instead, use really fine-tipped scissors to nibble at the base of the specimen, then gently pull it out, making an effort to keep the nail plate attached to the digit and avoid getting it stuck up in the punch.

Rule #5: Have dermatopathologists extensively experienced with nail pathology on your Rolodex

The histopathologic findings present in early subungual melanoma in situ are often too subtle for general dermatopathologists to appreciate, in Dr. Jellinek’s experience. He cited other investigators’ study of 18 cases of subungual melanoma in situ, all marked by longitudinal melanonychia. Only half showed the classic giveaway on the original nail matrix biopsy, consisting of a significantly increased number of atypical melanocytes with marked nuclear atypia. Blatant pagetoid spread was infrequent. However, all 18 cases displayed a novel, more subtle, and previously undescribed finding: haphazard and uneven distribution of atypical solitary melanocytes with variably sized and shaped hyperchromatic nuclei (J Cutan Pathol. 2016 Jan;43[1]:41-52).

Dr. Jellinek reported having no financial conflicts regarding his presentation. SDEF/Global Academy for Medical Education and this news organization are owned by the same parent company.