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A Case of Pigmented Longitudinal Melanonychia

Educational Objective
Based on this clinical scenario and the accompanying image, understand how to arrive at a correct diagnosis.
1 Credit CME

A man in his 40s presented to the dermatology clinic for evaluation of a new pigmented lesion on his left second toenail. The lesion first appeared 12 months before presentation and was progressively growing. This was his first time presenting to a physician for this problem, and no prior treatments had been attempted. The lesion was asymptomatic. He was otherwise well and denied any fevers or weight loss.

Clinical examination revealed a dark brown longitudinal pigment band covering the full length of the toenail of the left second digit with corresponding nail thickening over the pigmented band. The pigment was the same width throughout the band and extended to the proximal nail fold (Figure, A). No other nail or skin lesions were found at the time of examination. A biopsy specimen was obtained from the nail plate and nail matrix and stained with hematoxylin-eosin (Figure, B-D).

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A. Pigmented onychomatricoma

Histologic examination of the nail plate and nail matrix showed bland spindle cell proliferation within the nail matrix with invaginations of the epithelium. No melanocytic lesions were observed, and immunostaining was negative for S100 and CD34. Intracorneal hemorrhage and adjacent verrucous hyperkeratosis were present.

Based on the histologic findings of villous fibroepithelial projections into the nail plate without melanocytic proliferation or keratinocyte atypia, a diagnosis of pigmented onychomatricoma was made. The nail was surgically removed to fully excise the lesion after the original biopsy. At approximately 3 months of follow-up, the patient was doing well and without evidence of recurrence of the lesion.

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Article Information

Corresponding Author: Lisa Garner, MD, Department of Dermatology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390 (lisa@lisagarnermd.com).

Published Online: August 15, 2018. doi:10.1001/jamadermatol.2018.1894

Conflict of Interest Disclosures: None reported.

References
1.
Baran  R, Kint  A.  Onychomatrixoma: filamentous tufted tumour in the matrix of a funnel-shaped nail: a new entity (report of three cases).  Br J Dermatol. 1992;126(5):510-515. doi:10.1111/j.1365-2133.1992.tb11827.xPubMedGoogle ScholarCrossref
2.
Rushing  CJ, Ivankiv  R, Bullock  NM, Rogers  DE, Spinner  SM.  Onychomatricoma: a rare and potentially underreported tumor of the nail matrix.  J Foot Ankle Surg. 2017;56(5):1095-1098. doi:10.1053/j.jfas.2017.04.008PubMedGoogle ScholarCrossref
3.
Haneke  E, Fränken  J.  Onychomatricoma.  Dermatol Surg. 1995;21(11):984-987. doi:10.1111/j.1524-4725.1995.tb00538.xPubMedGoogle ScholarCrossref
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Miteva  M, de Farias  DC, Zaiac  M, Romanelli  P, Tosti  A.  Nail clipping diagnosis of onychomatricoma.  Arch Dermatol. 2011;147(9):1117-1118. doi:10.1001/archdermatol.2011.240PubMedGoogle ScholarCrossref
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Perrin  C, Goettmann  S, Baran  R.  Onychomatricoma: clinical and histopathologic findings in 12 cases.  J Am Acad Dermatol. 1998;39(4, pt 1):560-564. doi:10.1016/S0190-9622(98)70004-0PubMedGoogle ScholarCrossref
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Ocampo-Garza  J, Di Chiacchio  NG, Di Chiacchio  N.  Pigmented onychomatricoma: four cases.  Australas J Dermatol. 2018;59(1):e66-e69. doi:10.1111/ajd.12638PubMedGoogle Scholar
7.
Wynes  J, Wanat  KA, Huen  A, Mlodzienski  AJ, Rubin  AI.  Pigmented onychomatricoma: a rare pigmented nail unit tumor presenting as longitudinal melanonychia that has potential for misdiagnosis as melanoma.  J Foot Ankle Surg. 2015;54(4):723-725. doi:10.1053/j.jfas.2014.05.013PubMedGoogle ScholarCrossref
8.
Fayol  J, Baran  R, Perrin  C, Labrousse  F.  Onychomatricoma with misleading features.  Acta Derm Venereol. 2000;80(5):370-372. doi:10.1080/000155500459330PubMedGoogle ScholarCrossref
9.
Ishida  CE, Gouveia  BM, Cuzzi  T, Ramos-E-Silva  M.  Onychomatricoma: a case report with 5-year follow-up.  J Cutan Aesthet Surg. 2016;9(4):270-273. doi:10.4103/0974-2077.197084PubMedGoogle ScholarCrossref
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