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BLUE NEVUS (FINGERNAIL)

Introduction

Blue nevus is a congenital or acquired skin tumor that is generally benign and characterized by dermal proliferation of melanocytes. Blue nevus of the nail apparatus, or subungual blue nevus, is extremely rare. The lesions appear as solitary, small, deep-blue or blue-black macules or dome-shaped papules, and their color is the result of the Tyndall effect.  The Tyndall effect is the scattering of light which in this iesion is caused by the melanocytes. Subungual blue nevi have an excellent prognosis, but a biopsy may be necessary to rule out the possibility of a malignant melanoma, in which case, surgical excision may be required.1,2

Pathophysiology

  • Blue nevi may arise from aberrant dendritic melanocytes that fail to completely travel from the dermis to epidermis during embryologic development; inflammation, or other insults also may play a role in inducing melanocyte proliferation1
  • Their blue color is a result of the depth of melanin in the epidermis and the Tyndall effect, as dermal melanocytes absorb long wavelengths of light, and the skin reflects short wavelengths of the blue spectrum3

Related Anatomy

  • Epidermis
  • Dendritic melanocytes
  • Dermis
  • Melanin granules
  • Melanophages
  • Neural crest melanocytes
  • One histological classification system groups blue nevi into 3 types
    • Common: well-demarcated, slightly raised papules, often <1 cm in diameter, ranging in color from blue to black; most occur in the skin, commonly on the extremities and the face, but rare cases have been reported subungually
    • Cellular: less common and usually larger than common type nevi
    • Combined: displays features of both common and cellular types5
    • In most cases, blue nevi appear as solitary lesions, but multiple lesions, including some with a systematized distribution, have also been observed2

Incidence and Related Conditions

  • Subungual blue nevi are extremely rare; only 12 cases (6 in fingernails, 6 in toenails) have been documented between 1997 and 20171,6
  • In general, blue nevi are about twice as common in women than men, and they are typically noticed in the second decade of life or later2
  • Only one case of subungual blue nevus has been associated with a syndrome1

Differential Diagnosis

  • Argyria
  • Atypical blue nevus
  • Carney syndrome
  • Combined nevus
  • Deep penetrating nevus
  • Desmoplastic melanoma
  • Drug-induced (eg, minocycline, zidovudine) iatrogenic pigmentation
  • Foreign body
  • Glomus tumor
  • Benign longitudinal melanonychia*
  • Melanocytic nevus
  • Subungual malignant melanoma
  • Wilson’s disease

* Benign longitudinal melanonychia occurs in 1.4% of Caucasions. The most common location is the thumb.4

ICD-10 Codes

  • BLUE NEVUS (FINGERNAIL)

    Diagnostic Guide Name

    BLUE NEVUS (FINGERNAIL)

    ICD 10 Diagnosis, Single Code, Left Code, Right Code and Bilateral Code

    DIAGNOSISSINGLE CODE ONLYLEFTRIGHTBILATERAL (If Available)
    BLUE NEVUS (FINGERNAIL)(NON-NEOPLASTIC)I78.1   

    ICD-10 Reference

    Reproduced from the International statistical classification of diseases and related health problems, 10th revision, Fifth edition, 2016. Geneva, World Health Organization, 2016 https://apps.who.int/iris/handle/10665/246208

Clinical Presentation Photos and Related Diagrams
Blue Nevis
  • Blue Nevus Thumb Nail
    Blue Nevus Thumb Nail
Symptoms
Subungual Pain
Subungual dark longitudinal line
Typical History

The typical patient is a children or young adult complaining of a pigmented band in the thumb nail.  The color varies from light brown to black. The band is narrow, less than 3mm wide.4

Positive Tests, Exams or Signs
Work-up Options
Treatment Options
Treatment Goals
  • Establish an accurate daignosis and treatment the lesion with out deforming the nail.
Conservative
  • No definitive treatments have been established, and more cases are necessary to identify optimal management strategies
Operative
  • Biopsy maybe needed to rule out malignant melanoma.
  • Complete excision
    • May be recommended if the blue nevus is expanding in size to reduce the possibility of malignant changes and to produce a better cosmic result5
    • Excision of larger blue nevi may increase the risk of nail dystrophy or functional impairment of the affected digit1
    • The possibility of nail dystrophy or digital functional impairment after excision should be kept in mind before radical surgical removal is recommended3
    • Malignant changes should also be considered when recurrence occurs after excision
Treatment Photos and Diagrams
Blue Nevus excision from thumb nail
  • Blue Nevus Thumb Nail - Nailplate being removed
    Blue Nevus Thumb Nail - Nailplate being removed
  • Blue Nevus Thumb Nail - melanotic changes in sterile matrix
    Blue Nevus Thumb Nail - melanotic changes in sterile matrix
  • Blue Nevus Thumb Nail - Partial excision of melanotic area
    Blue Nevus Thumb Nail - Partial excision of melanotic area
  • Blue Nevus Thumb Nail-Sterile matrix repair and germinal matrix preserved
    Blue Nevus Thumb Nail-Sterile matrix repair and germinal matrix preserved
Complications
  • Nail dystrophy
  • Functional impairments of affected finger
Outcomes
  • The majority of blue nevi are benign and have a good prognosis
  • Subungual malignant melanoma carries a poor prognosis, highlighting the importance of making an accurate diagnosis that considers melanoma3
Key Educational Points
  • The term “blue naevus’’ was originally used to describe dark-blue lesions of the skin, and was introduced into the literature in 19067
  • The first case of subungual blue nevus was described in 1997, when a 20-year-old man presented with a subungual congenital circumscribed pigmented lesion that had recently enlarged, elevated the distal nail plate, and become painful5
  • Clinical signs of enlargement, nail dystrophy, or periungual extension with cellular type histopathology must encourage the consideration of conservation excisionor biopsy
  • Dermoscopy may be helpful for distinguishing subungual blue nevi from subungual malignant melanoma, especially in the presence of a blue discoloration in and around the single nail unit3,4
  • Blue Nevus will not have a podsitive Hutchinson sign
References

Cited

  1. Klufas DM, Que SK, Berke A, Maryland BS. Acquired blue nevus of the nail bed. Dermatol Online J 2017;23(2). PMID: 28329489
  2. Causeret AS, Skowron F, Viallard AM, et al. Subungual blue nevus. J Am Acad Dermatol 2003;49(2):310-2. PMID: 12894085
  3. Gershtenson PC, Krunic A, Chen H, et al. Subungual and periungual congenital blue naevus. Australas J Dermatol 2009;50(2):144-7. PMID: 19397572
  4. Haenssle HA, BlumA et al. When all you have is a dermascope - start looking at nails. Dermol Pract Concept. 2014; 4(4):2, http://dx.doi.orglio.5826/dpc.0404a02.
  5. Lee EJ, Shin MK, Lee MH. A subungual blue naevus showing expansile growth. Acta Derm Venereol 2012;92(2):162-3. PMID: 21879242Vidal S, Sans A, Hernandez B, et al. Subungual blue nevus. Br J Dermatol 1997;137:1023-5. PMID: 9470936
  6. Tieche M. Über benigne Melanoma (‘Chromatophorome”) der Haut- “blaue Naevi”. Virchows Arch Patho Anat 1906;186:212–29[LG1] .

New Articles

  1. Klufas DM, Que SK, Berke A, Maryland BS. Acquired blue nevus of the nail bed. Dermatol Online J 2017;23(2). PMID: 28329489
  2. Haenssle HA, BlumA et al. When all you have is a dermascope - start looking at nails. Dermol Pract Concept. 2014; 4(4):2, http://dx.doi.orglio.5826/dpc.0404a02.

Classics

  1. Tieche M. Über benigne Melanoma (‘Chromatophorome”) der Haut- “blaue Naevi”. Virchows Arch Patho Anat 1906; 186: 212–29.
  2. Vidal S, Sans A, Hernandez B, et al. Subungual blue nevus. Br J Dermatol 1997;137:1023-5. PMID: 9470936
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