Suspected melanonychia in pediatric patients can confound physicians

Key Points

Miami - Differentiating benign nail pigmentations such as melanonychia from either nail or nail matrix melanoma is especially difficult in children because pediatric lesions present differently than they do in adults, according to Antonella Tosti, M.D., professor of the department of dermatology and cutaneous surgery, University of Miami Miller School of Medicine.

"Though a long list of nail disorders can occur in children and adolescents, all of which have their own individual difficulties and challenges regarding management and treatment, nail pigmentations in children are probably one of the most distressing problems because of the rare, nevertheless ominous, differential diagnosis of nail melanoma," Dr. Tosti says.

Melanonychia presents as a longitudinal brown or black pigmented streak along the nail. The lesion can be due to a variety of causes, Dr. Tosti says, including physiologic longitudinal melanonychia, systemic disorders, inflammatory nail disorders, onychomycosis, Bowen's disease, drugs, benign melanocytic hyperplasias or melanoma.

An accurate differential diagnosis between melanonychia and nail matrix melanoma in the pediatric population poses challenges because nevi occurring in children often possess dermoscopic features that can mimic those seen in malignant lesions - even if the lesion is benign, Dr. Tosti says.

"Pigmented lines viewed in the dermoscope which are not parallel or not regularly organized, or thicker layers of pigmentation are all universal signs that are suggestive of a malignancy. In children, the irregular organization of lines in a pigmented lesion seen on dermoscopy may also be seen in benign melanonychia, making it very difficult to accurately judge and arrive at a definitive diagnosis," Dr. Tosti says.

Although an enlarging pigmented lesion under the nail in adults would be a cause for worry, it is very common for subungual lesions to enlarge in children, even if the lesion is benign, she says.

Clinical features in pediatric nevi that may cause alarm include pseudo-Hutchinson sign, involvement of the nail folds and hyponychium (often seen in congenital nevi), darkening and spreading of the pigmentation, and a thinning and fissuring of the pigmented nail plate, Dr. Tosti says. All of these can raise suspicions during clinical assessment.

Considering biopsy

Lesion biopsy remains one of the cornerstone approaches in the diagnosis and management of suspicious nail pigmented lesions, but performing biopsies in children can be difficult because of patient fear and the resulting frequent need for sedation, she says.

"An excisional biopsy is recommended for a diagnosis based on pathological evaluation of the whole lesion. The shave biopsy of the nail matrix is possibly the best technique to evaluate the whole lesion and provide accurate diagnosis without leaving a definitive nail dystrophy," Dr. Tosti says.

What's more, clinical and dermoscopic criteria regarding nail melanoma in children have not been established, and punch biopsy of a suspicious lesion is often inadequate to rule out the diagnosis of nail melanoma, she explains.

Just as in adults, physicians should not biopsy all melanonychia lesions in children, Dr. Tosti says. If there is no immediate concern or worry, she says she may observe the lesion every six months and only remove the lesion after puberty.

She says she would consider excising lesions in which the band enlarges, becomes darker, or if the nail plate shows some abnormality such as fissuring.

"Treatment and management choices are often difficult in melanonychia in children and there is no one-size-fits-all approach," Dr. Tosti says. "I believe that each case should be treated and assessed individually, and clinicians should carefully weigh all of the diagnostic parameters and pathological factors before choosing a therapeutic approach."

Disclosures: Dr. Tosti reports no relevant financial interests.