When to see red in linear erythronychia — Malignant onychopapilloma

By Warren R. Heymann, MD, FAAD
June 29, 2022
Vol. 4, No. 26

With every passing year, I take increasing comfort in the stability of the linear erythronychia of my left fifth digit. The presumed diagnosis of an onychopapilloma (OP) is very reassuring because every article I ever read about the neoplasm clearly states its benignancy. My spontaneous visceral response upon reading a case report entitled “Malignant Onychopapilloma” (1) was “say it ain’t so!”

In 1995, Baran and Perrin observed 4 similar cases of monodactylous distal subungual keratosis with the following characteristics: 1) absence of Darier disease; 2) presence of multinucleate cells histologically; and 3) localized distal subungual keratosis without a granular layer. They named this lesion “localized multinucleate distal subungual keratosis.” (2) Five years later, the authors suggested changing the name of this lesion to OP because only 2 cases demonstrated multinucleated cells. Of 16 cases of longitudinal erythronychia, 14 were found to have OP and 2 had Bowen’s disease of the nail. (3)

In their retrospective analysis of 47 patients with OP, Tosti et al found that the most common clinical presentation was longitudinal erythronychia (n = 25); followed by longitudinal leukonychia (n = 7); longitudinal melanonychia (n = 4); long splinter hemorrhages without erythronychia, leukonychia, or melanonychia (n = 8); and short splinter hemorrhages without erythronychia, leukonychia, or melanonychia (n = 3), with subungual mass (n = 47) and distal fissuring (n = 11). Pathology was consistent with acanthosis of the nail bed and distal matrix, with matrix metaplasia underlying distal subungual hyperkeratosis. The authors also demonstrated that dermoscopy of the free edge of the nail plate reveals a small subungual keratotic mass where the band reaches the nail plate margin, providing a clue for the diagnosis. (4) The clinical presentation of OP appears to be strongly linked to skin of color, with cases of erythronychia or leukonychia being most common in White patients, while melanonychia being more frequently observed in Asian, Hispanic, Black, and Indian patients. (5)

Ops are usually seen in adults but may be observed in the adolescent and pediatric population. As most cases present as monodactylous linear erythronychia (LE), it is essential to consider other disorders in the differential diagnosis, including verruca, warty dyskeratoma, glomus tumor, Bowen’s disease, melanoma, basal cell carcinoma, and other vascular lesions including arteriovenous malformation. According to Beggs et al, “Management of monodactylous LE should be based on the patient’s symptoms or changes in the lesion. Symptomatic lesions should be surgically excised. Sudden onset or changing LE should be biopsied, whereas stable LE can be measured, photographed, and reevaluated in a few months. Multiple LE lesions on the same digit may warrant radiographs or magnetic resonance imaging, depending on the clinical suspicion of a more invasive local process. Longitudinal nail unit excisions that include the length of the lesion are recommended for LE.” (6)

The pathogenesis of OP remains speculative, with hypotheses including a neoplastic process or as a reactive hyperplasia in response to trauma or inflammation (such as lichen planus). (7) Erythronychia is due to thinning of the nail plate, melanonychia is secondary to melanocyte activation, and leukonychia because of altered refraction of light.

The case report of the malignant OP by Haneke et at was a 58-year-old man with a linear longitudinal lesion of the right thumbnail that had been present a few years, but had become painful in the months prior to presentation. Proximal LE and distal yellow with onycholysis and subungual hyperkeratosis was noted. A longitudinal excision demonstrated cellular atypic and pathologic mitoses in the distal matrical portion of the lesion and proximal nailbed epithelium. HPV typing was negative. The authors noted that it cannot be determined if this was a primary malignant OP or malignant degeneration of previously benign OP. (8)

In their superlative review of nail tumors, Hare and Rich state: “Nail tumor assessment generally follows the basic tenets of skin tumor assessment: lesions with rapid growth, tenderness, and destructiveness warrant further exploration.” (9) Rubin et al, in their editorial regarding malignant OP, pose the question if this changes the management and clinical approach to monodactylous LE. Their answer — “it doesn’t! in general, asymptomatic stable monodactylous longitudinal erythronychia can be observed. The reason that this patient underwent excision of this lesion was that it was painful.”

Dr. Rubin put me at ease. I look forward to decades more staring at my asymptomatic LE. Should it become painful, I know what needs to be done.

Point to Remember: Onychopapillomas are usually benign, most frequently presenting as linear erythronychia with distal subungual hyperkeratosis. Lesions can usually be observed, but should they become painful or demonstrate obvious change, an excisional biopsy is warranted.

Our experts’ viewpoint

Elizabeth Yim, MD, MPH, FAAD
Assistant Professor, UCLA Dermatology

John Montgomery Yost, MD, MPH, FAAD
Clinical Associate Professor and Director, Nail Disorders Clinic, Stanford University
Department of Dermatology

Nail tumors are often difficult to assess compared to their skin counterparts. Furthermore, not all dermatologists are comfortable diagnosing nail disorders as specific training on nails varies in residency programs. The etiology of onychopapilloma remains controversial, and while it most commonly presents as longitudinal erythronychia (LE), other clues include splinter hemorrhages and presence of a wedge-shaped notch under the nail plate that corresponds to the LE band. Other findings such as longitudinal leukonychia and even longitudinal melanonychia can also be observed. 

In cases of LE, we must always keep Bowen’s tumor in the back of our minds. However, the LE of Bowen’s disease tends to be larger than 1 mm, streaky, and irregular in appearance. We agree with Beggs et al.: “Management of monodactylous LE should be based on the patient’s symptoms or changes in the lesion.” (6) Any sudden changes or association with pains should be closely examined and biopsied or surgically excised. If LE is stable, patients can be reassured and monitored closely with photos and re-evaluated every few months. Should one be concerned about a more invasive process, imaging such as MRI or US can be done for further evaluation. 

1. Haneke E, Iorizzo M, Gabutti M, Beltraminelli H. Malignant onychopapilloma. J Cutan Pathol. 2021 Jan;48(1):174-179.

2. Baran R, Perrin C. Localized multinucleate distal subungual keratosis. Br J Dermatol. 1995 Jul;133(1):77-82.

3. Baran R, Perrin C. Longitudinal erythronychia with distal subungual keratosis: onychopapilloma of the nail bed and Bowen's disease. Br J Dermatol. 2000 Jul;143(1):132-5.

4. Tosti A, Schneider SL, Ramirez-Quizon MN, Zaiac M, Miteva M. Clinical, dermoscopic, and pathologic features of onychopapilloma: A review of 47 cases. J Am Acad Dermatol. 2016 Mar;74(3):521-6.

5. Hashimoto H, Ito T, Yamada Y, Oda Y, Furue M. Onychopapilloma presenting as longitudinal melanonychia: A case report and literature review. Australas J Dermatol. 2021 Feb 1. doi: 10.1111/ajd.13543. Epub ahead of print. PMID: 33527379.

6. Beggs S, Butala N, Heymann WR, Rubin AI. Onychopapilloma Presenting as Longitudinal Erythronychia in an Adolescent. Pediatr Dermatol. 2015 Jul-Aug;32(4):e173-4.

7. Kim M, Sun EY, Jung HY, Cho BK, Park HJ. Onychopapilloma: A Report of Three Cases Presenting with Various Longitudinal Chromonychia. Ann Dermatol. 2016 Oct;28(5):655-657.

8. Haneke E, Iorizzo M, Gabutti M, Beltraminelli H. Malignant onychopapilloma. J Cutan Pathol. 2021 Jan;48(1):174-179.

9. Hare AQ, Rich P. Nail Tumors. Dermatol Clin. 2021 Apr;39(2):281-292.

10. Rubin AI, Lee D, Baran R. Malignant onychopapilloma: A new nail unit clinicopathologic entity. J Cutan Pathol. 2021 Mar;48(3):347-348. doi: 10.1111/cup.13941. Epub 2021 Jan 7. PMID: 33368490.

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