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This retrospective study of 163 biopsies of longitudinal melanonychia found a 22% malignancy rate, including 22 malignant melanoma, 11 melanoma in situ, and 1 squamous cell carcinoma. The left thumb and bilateral first toes were the most commonly involved digits. The number needed to biopsy to find a malignancy was fewer than 5.
The findings of this study suggest that patients with concerning longitudinal melanonychia should undergo biopsy analysis to rule out nail apparatus melanoma.
Longitudinal melanonychia (LM) is a common dermatologic examination finding, with various benign and malignant underlying etiologies. Biopsy analysis for histopathologic examination is the diagnostic standard. Biopsy overuse can lead to negative effects, including permanent nail dystrophy. However, underuse of biopsy leads to risk of delayed diagnosis of melanomas and poor outcomes. We conducted a single-center, retrospective review of the electronic medical and pathology records for patients aged >18 years with the clinical finding of LM who underwent nail biopsy between January 2000 and August 2022. We evaluated the characteristics of LM from different etiologies and calculated the number needed to biopsy (NNB) as 1/p, with p representing the number of malignancies biopsied divided by total number of biopsies.
As the experts in hair, skin, and nails, one of the most important features of our profession is our ability to diagnose and manage cutaneous malignancies. Naturally, our patients expect the expertise with which we evaluate cutaneous lesions to extend to the management of acral malignancies. Despite patient and professional expectations, myriad data exist showing that nail melanoma carries higher morbidity and mortality than cutaneous melanoma, likely due to a reticence to biopsy and resultant later stage at diagnosis.1
Bender et al’s original manuscript provides an important retrospective review of nail biopsies for longitudinal melanonychia at their institution over a 22-year period, establishing a number needed to biopsy of four patients in order to diagnose a nail malignancy. There are limitations to this study due to its retrospective nature as well as selection bias. It would be interesting to note the number of patients presenting with melanonychia where the decision was made not to biopsy and the long-term outcome and followup of these patients as well. The take home point of this study, however, is salient: evaluate nails critically and biopsy often.
Barriers to nail biopsy are multifactorial, including psychological barriers for the patient as well as technical barriers for the clinician. Lee et al found that one-third of graduating third year dermatology residents reported a lack of competency in nail procedures upon completion of training.2 Of the over 150 dermatology programs in North America, only a handful offer exposure to a dedicated nail clinic with dedicated nail teaching. These factors often lead to a “watch and wait” approach to pigmented bands of the nail unit, something we will not tolerate on analogous cutaneous lesions.
In reading Bender et al’s manuscript, my advice is to seek out nail training experiences, be that dedicated visiting mentorships through specialty organizations such as the Council for Nail Disorders or the AAD’s Annual Meeting and Summer Innovation Academy hands-on cadaver nail surgery course, which has been shown to durably increase participants’ competence in nail surgery.3 If one isn’t interested or able to perform nail procedures, it is incumbent on the dermatologist to seek out those local colleagues who perform these technically demanding procedures with frequency in order to appropriately triage those patients with concerning bands of melanonychia.
1. Zhang J, Yun SJ, McMurray SL, et al. Management of Nail Unit Melanoma. DermatolClin. 2021;39(2):269-280. https://www.sciencedirect.com/science/article/abs/pii/S0733863520301091?via%3Dihub
2. Lee EH, Nehal KS, Dusza SW, et al. Procedural dermatology training during dermatology residency: a survey of third-year dermatology residents. J Am Acad Dermatol. 2011;64(3):475-483. https://www.jaad.org/article/S0190-9622(10)00692-4/fulltext
3. Stiff KM, Jellinek NJ, Knackstedt TJ. Hands-On Nail Surgery Workshop Leads to Sustained Improvement in Comfort With Nail Surgery. Dermatol Surg. 2021;47(12):1670-1671. https://journals.lww.com/dermatologicsurgery/Citation/2021/12000/Hands_On_Nail_Surgery_Workshop_Leads_to_Sustained.44.aspx