Dermatology: Practical and Conceptual


Image Letter | Dermatol Pract Concept. 2023;13(1):e2023062 1

Longitudinal Melanonychia as the Only Sign  
of in Situ Squamous Cell Carcinoma

José Alberto García-Lozano1, Gabriel Salerni2, Jesus Alberto Cardenas-de la Garza3,  
María Rosa Perez4, Francisco Guillermo Schreiber4

1 Universidad Autónoma de Nuevo León, Departamento de Introducción a la Clínica, Facultad de Medicina y Hospital Universitario “Dr. José 

E. González’’, Monterrey, Nuevo León, Mexico

2 Dermatology Department, Hospital Provincial del Centenario de Rosario, Universidad Nacional de Rosario, Santa Fe, Argentina

3 Universidad Autónoma de Nuevo León, Servicio de Reumatología, Facultad de Medicina y Hospital Universitario “Dr. José E. González’’, 

Monterrey, Nuevo León, México

4 Private practice, Resistencia, Chaco, Argentina

Citation: García-Lozano JA, Salerni G, Cardenas-de la Garza JA, Perez MR, Schreiber FG. Longitudinal Melanonychia As The Only Sign 
Of In Situ Squamous Cell Carcinoma. Dermatol Pract Concept. 2023;13(1):e2023062. DOI: https://doi.org/10.5826/dpc.1301a62

Accepted: August 28, 2022; Published: January 2023

Copyright: ©2023 García-Lozano et al. This is an open-access article distributed under the terms of the Creative Commons Attribution-
NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, 
distribution, and reproduction in any medium, provided the original authors and source are credited.

Funding: None.

Competing Interests: None.

Authorship: All authors have contributed significantly to this publication.

Corresponding Author: José Alberto García-Lozano, MD, Universidad Autónoma de Nuevo León, Departamento de Introducción a la 
Clínica, Facultad de Medicina y Hospital Universitario “Dr. José E. González’’, Monterrey, Nuevo León, México. Tel: 81 8329 4154  
E-mail: dr.josealbertogarcia@gmail.com

Case Presentation

A 39-year-old man was consulted because of a 2-year history 

of a pigmented lesion in his right thumbnail (Figure 1A). His 

personal history was remarkable for previous genital human 

papillomavirus (HPV) infection. Onychoscopy revealed a 

pigmented longitudinal melanonychia that affected the cuti-

cle to the distal edge of the nail plate with no other signs or 

symptoms (Figure 1B). Complete excision of the lesion with 

narrow margins was performed because of a suspicion of 

malignancy. Histological examination revealed in situ squa-

mous cell carcinoma (SCC).

Teaching Point

SCC and in situ SCC are the most common malignant 

tumors of the nail [1]. This disease is often misdiagnosed 

with other common infectious or inflammatory nail dis-

eases due to its multiple clinical presentations. Melanony-

chia has always been a challenging sign for dermatologists. 

Longitudinal melanonychia is often associated with benign 

or malignant melanocytic proliferation, and nail unit mel-

anoma (NUM) should always be ruled out [2]; therefore, 

dermoscopy of the nail apparatus (onychoscopy) is an in-

dispensable tool in the evaluation of pigmented nail lesions. 

Any unexplained melanonychia of a single digit in white-

skinned individuals should be biopsied to rule out NUM; 

however, this case demonstrates that nail unit in situ SCC 

can also present exclusively as longitudinal melanonychia 

with no other deformity or periungual lesion and should 

always be included in the differential diagnosis when longi-

tudinal melanonychia is present.



2 Image Letter | Dermatol Pract Concept. 2023;13(1):e2023062

References

1. Starace M, Alessandrini A, Dika E, Piraccini BM. Squa-

mous cell carcinoma of the nail unit. Dermatol Pract Con-

cept. 2018;8(3):238-244. DOI:  10.5826/dpc.0803a17. 

PMID: 30116671. PMCID: PMC6092066.

2. Singal A and Bisherwal K. Melanonychia: Etiology, Diagnosis, 

and Treatment. Indian Dermatol Online J. 2020;11(1):1-11. 

DOI:  10.4103/idoj.IDOJ_167_19. PMID:  32055501. PMCID: 

PMC7001389.

Figure 1. (A) Clinical image of the pigmented lesion in the right thumb nail. (B) Onychoscopy of the lesion demonstrates a brown-

dark, homogeneous, pigmented, longitudinal melanonychia. Hutchison and micro-Hutchinson signs absent.