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Context.—: Acral lentiginous melanoma is a rare and aggressive type of cutaneous melanoma that arises on the acral skin and the nail unit. The prognostic significance of subungual anatomic site in acral lentiginous melanoma is not established., Objective.—: To assess the impact of subungual anatomic site on overall survival and disease-specific survival in acral lentiginous melanoma., Design.—: Retrospective cohort analysis. Clinicopathologic characteristics of 627 primary acral lentiginous melanomas (45 [7%] subungual and 582 [93%] nonsubungual) were summarized, and the impact of these characteristics on overall survival and disease-specific survival was determined using univariate and multivariable analyses., Results.—: No significant differences in clinicopathologic features were identified between the subungual and nonsubungual acral lentiginous melanomas. The 1-, 5-, and 10-year overall survival rates were 81%, 40%, and 28%, respectively, for subungual acral lentiginous melanoma and 94%, 59%, and 38%, respectively, for nonsubungual acral lentiginous melanoma (P = .04); risk of death was significantly higher for subungual tumors (hazard ratio [95% confidence interval] = 1.59 [1.02-2.50]; P = .04). The 1-, 5-, and 10-year disease-specific survival rates were 94%, 56%, and 48%, respectively, for subungual acral lentiginous melanoma versus 96%, 69%, and 55%, respectively, for nonsubungual acral lentiginous melanoma (P = .18). By multivariable analysis, independent poor prognostic factors included older age and ulceration for overall survival and greater Breslow thickness and sentinel lymph node positivity for overall survival and disease-specific survival. Subungual anatomic site was not an independent prognostic factor for overall or disease-specific survival., Conclusions.—: Subungual anatomic site is not an independent prognostic factor for acral lentiginous melanoma., Competing Interests: The authors have no relevant financial interest in the products or companies described in this article at https://meridian.allenpress.com/aplm in the August 2021 table of contents.

Background: Pachyonychia congenita (PC) is a rare autosomal dominant disorder of keratinization mediated by genetic mutations in KRT6A, KRT6B, KRT6C, KRT16, or KRT17. While nail dystrophy in PC has a significant impact on quality of life, the histopathological features of the nail plate in PC have not been previously reported. We report the histopathological features of nail plates provided by 19 patients with genetically confirmed PC., Methods: Nineteen patients with genetically confirmed PC provided a total of 56 nail plates for histopathologic examination. The nail plates were examined for the presence of hyphae, yeast, bacteria, neutrophils, parakeratosis, plasma globules, and hemorrhage. Specimens with onychomycosis (three patients) were excluded from the analysis., Results: No specific histopathological feature was identified in PC nails. Parakeratosis and plasma globules were the most prominent features in both clinically affected and unaffected PC nails. There was a significant association between clinical dystrophy of all 20 nails and KRT6A mutations, and a lack of dystrophy of all 20 nails in KRT6B mutations., Conclusions: Parakeratosis and plasma globules in the absence of other inflammatory disorders should raise PC in the histopathologic differential diagnosis. The presence of onychomycosis in a nail plate does not exclude a diagnosis of PC., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Pigmented onychomatricoma is a rare nail unit tumor that can clinically mimic nail unit melanoma. We report the case of a 63-year-old male with new-onset longitudinal melanonychia involving his right second toe. An excisional biopsy was performed and demonstrated pigmented onychomatricoma. We present this case to alert clinicians of this rare nail unit tumor and the importance of clinicopathologic correlation to avoid misdiagnosis., (Copyright © 2015 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.)

"Nail clipping is a simple technique for diagnosis of several nail unit dermatoses. This article summarizes the practical approach, utility, and histologic findings of a nail clipping in evaluation of onychomycosis, nail unit psoriasis, onychomatricoma, subungual hematoma, melanonychia, and nail cosmetics, and the forensic applications of this easily obtained specimen. It reviews important considerations in optimizing specimen collection, processing methods, and efficacy of special stains in several clinical contexts. Readers will develop a greater understanding and ease of application of this indispensable procedure in assessing nail unit dermatoses.", (Copyright © 2015 Elsevier Inc. All rights reserved.)

The authors herein describe several nail conditions, which the general pediatrician is likely to encounter in the course of routine practice. Because pediatric nail disorders represent a limited component of a general pediatric practice, it can be challenging for practitioners to establish expertise in the diagnosis and treatment of these conditions and to recognize when reassurance is appropriate or when referral to a specialist is necessary. This article summarizes the anatomy of the normal nail unit, as well as the evaluation and management of onychomycosis, melanonychia, trachyonychia, onychomadesis, and nail pitting., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Localized longitudinal erythronychia describes a solitary red streak limited to a single nail unit. Localized longitudinal erythronychia can be caused by both benign and malignant entities. Most commonly, the cause is a benign process, such as an onychopapilloma. We report a case of an acquired subungual arteriovenous malformation that presented as localized longitudinal erythronychia during pregnancy. To our knowledge, this is the first report of localized longitudinal erythronychia arising from a pregnancy-associated arteriovenous malformation of the nail unit., (Copyright © 2012 John Wiley & Sons A/S.)

Nail unit dermatopathology is a growing field filled with many challenges. Many advances in this field have been made in the last 5 years. This review article provides an update on new information and studies published in that period of time. We divided these works into different sections, including clinical and pathologic challenges in diagnosis and treatment of nail disorders, nail unit biopsy and processing techniques, normal nail unit histology, nail plate structural and growth pathology, metabolic disease, inflammatory conditions, onychomycosis, benign growths, malignant growths, and dyschromias. Specific highlights include advances in the marking and orientation of nail unit biopsies for improved histologic interpretation, improved nail plate softening techniques, new methods for histologic evaluation of onychomycosis, descriptions of newly described benign growths unique to the nail unit, and the morphologic and immunohistochemical distinction between benign and malignant pigmented lesions of the nail unit., (© 2012 Wiley Periodicals, Inc.)

Herein, we describe some of the more common changes in the nail unit that can be seen in systemic diseases in children. Changes that can be seen are not limited to those discussed in the following pages. The presence of changes on multiple nails is suggestive of a systemic cause in an ill child. However, multiple nails can also be affected in primary inflammatory disorders and infections of the nail unit. When evaluating a pediatric patient with a nail disorder, it is important to perform a complete physical examination of the skin and oral mucosa, as other clues to the diagnosis of the nail problem may be found. A comprehensive family history is also important to uncover possible syndromic associations with nail disease or diseases that can manifest with nail changes., (Copyright © 2012 Mosby, Inc. All rights reserved.)

An otherwise-healthy 13-year-old girl with previously normal nails developed longitudinal pigmented bands on multiple fingernails. Physical examination revealed faintly pigmented bands on multiple fingernails and on the left fifth toenail. We believed that the cause of the pigmented bands was onychophagia-induced longitudinal melanonychia, a rare phenomenon, which emphasizes the need for dermatologists to question patients with melanonychia about their nail biting habits because they may not be forthcoming with this information., (© 2011 Wiley Periodicals, Inc.)

Nail cosmetics and adornments are widely used in today's society. However, their histologic features are not well characterized. Routine histologic examination and polarization of nail plate specimens in our academic dermatopathology practice at the Hospital of the University of Pennsylvania revealed 3 distinct histologic patterns of nail cosmetics: a hyperpigmented pattern with diffuse fine granular material, a layered pattern with a single linear band of polarizable material, and a hyperpigmented pattern with larger granules containing flecks of polarizable material. In our experience, submitting clinicians rarely indicate the patient's use of nail polish or other enhancements. Recognition of the histologic features of nail cosmetics is important to prevent confusion with dermatoses affecting the nail unit, and it will help dermatopathologists render more accurate diagnoses.