An Atlas of Lumps and Bumps, Part 43: Blue Nevi

Blue Nevi

Blue nevi are benign neoplasms composed of dermal melanocytes presenting as papules, nodules or, rarely, plaques of blue, blue-gray, or blue-black color.¹ Histologically, the lesion is characterized by a proliferation of spindled and dendritic melanocytes in a focal area of the reticular dermis.

In the majority of cases, blue nevi are acquired and frequently arise in adolescence.¹ They can, however, occur at any age or as a congenital lesion.^2,3 In addition to the usual sporadic occurrence, congenital blue nevi may be familial or associated with Carney complex also known as NAME (nevi, atrial myxoma, myxoid neurofibromas, ephelides) syndrome or LAMB (lentigines, atrial myxomas, blue nevi) syndrome.⁴ Blue nevus occurs in approximately 3% of Japanese and 0.5 to 4% of White adults.⁵ The male-to-female ratio is approximately 1:2.^1,4,6

It is believed that a blue nevus results from a dermal arrest in the migration of neural crest melanocytes during fetal development with subsequent proliferation of these melanocytes.⁷ This is supported by the fact that melanocytes in the blue nevus typically stain positive for Human Melanoma Black-45 (HMB-45).⁸ The majority of blue nevi have a somatic mutation in the GNAQ or GNA11genes that encode the G-protein α-subunits.^9,10 Blue nevi with mutations in KRAS or CYSLTR2 genes have also been reported.^9-11 Predisposing factors or triggers include sunburns, trauma, vesiculobullous dermatoses, and oral contraceptives.^12,13

Several variants of blue nevi have been described; the two main ones being common blue nevus (also known as dendritic blue nevus) and cellular blue nevus.¹⁰ The common blue nevus typically presents as a solitary, smooth, well-demarcated, dome-shaped papule or nodule that measures less than 10 mm in diameter.^1,10 The lesion is homogeneously blue to blue-gray to dark-blue in color and is asymptomatic.^1,10 The characteristic blue color (ceruloderma) can be attributed to the deep dermal location of melanin which results in the shorter wavelength blue light reflected back to the observer (Tyndall effect).^1,10 Sites of predilection include the face (Figure 1), and dorsal surfaces of the hands and feet (Figure 2).¹⁰ Rarely, they may occur in the subungual area, conjunctiva, oral mucosa, sino-nasal mucosa, orbit, esophagus, bronchus, lymph nodes, endometrium, uterine cervix, vagina, penis, and prostate.^6,7,14,15

Fig. 1 One of the sites of predilection for blue nevi include the face as shown here.


Fig. 2 The lesion is homogeneously blue to blue-gray to dark-blue in color and is asymptomatic.

The cellular blue nevus is less common and is larger (typically 10 to 30 mm in diameter), more elevated, often more heavily pigmented, and has a more irregular surface (Figure 3).¹⁰ Sites of predilection include the scalp, face, buttocks, sacrococcygeal region, and extremities.^3,4

Fig. 3 The cellular blue nevus is a variant of blue nevi and is typically 10 to 30 mm in diameter, more elevated, often more heavily pigmented than blue nevi.

Rarely, blue nevi with peripheral satellitosis have also been described.¹⁶ A blue nevus with satellite lesions is an ominous indicator of potential malignant change and should be differentiated from a malignant melanoma with cutaneous metastases.^17-19

The plaque-type variant is usually present at birth or in early childhood and may enlarge at puberty.^6,20 The lesion is usually blue-gray and composed of a single plaque or a confluence of several small macules, papules and/or nodules.^6,21 Sites of predilection include the trunk followed by the scalp.^19,21 An important characteristic of a plaque-type blue nevus is the formation of subcutaneous cellular nodules which have the potential to develop into melanoma.^20,22

Epithelioid blue nevus is a distinctive variant of blue nevus characterized by a predominately dermal proliferation composed of heavily pigmented epithelioid melanocytes with fewer nonpigmented to minimally pigmented spindled melanocytes.²³ Clinically, an epithelioid blue nevus presents as a solitary, heavily pigmented, blue-black, dome-shaped nodule, or as multiple nodules.⁸  Multiple epithelioid blue nevi have a strong association with Carney complex.^8,23

Other rare variants include hypopigmented/amelanotic blue nevus, compound blue nevus, targetoid blue nevus, agminated blue nevus, linear blue nevus, sclerosing blue nevus, eruptive blue nevi, and disseminated blue nevi.^{3,4,10,13,24-29}

The diagnosis is a clinical one based on the characteristic features which can be aided by dermoscopy. Dermoscopy typically shows a bluish or steel-blue, well-circumscribed, homogeneous, structureless pigmentation secondary to the presence of heavily pigmented melanocytes in the dermis.^30-32 Polarized dermoscopy may show striking color changes of yellow, pink, green, and purple resembling the colors of a rainbow.³³

A blue nevus can be cosmetically unsightly and an esthetic concern if it occurs in an exposed area. A halo phenomenon associated with a blue nevus is rare and the nevus tends to persist unlike the halo phenomenon in other melanocytic nevi.³⁴ Malignant transformation is also rare but should be considered if there is a sudden increase in size of the lesion, deepening of color, asymmetry of the lesion, irregular border, or recurrence after the excision of the lesion.^4,35

AUTHORS:
Alexander K.C. Leung, MD^1,2, Benjamin Barankin, MD³, Joseph M. Lam, MD⁴, Kin Fon Leong, MD⁵

AFFILIATIONS:
¹Clinical Professor of Pediatrics, the University of Calgary, Calgary, Alberta, Canada
²Pediatric Consultant, the Alberta Children’s Hospital, Calgary, Alberta, Canada
³Dermatologist, Medical Director and Founder, the Toronto Dermatology Centre, Toronto, Ontario, Canada
⁴Associate Clinical Professor of Pediatrics, Dermatology and Skin Sciences, the University of British Columbia, Vancouver, British Columbia, Canada.
⁵Pediatric Dermatologist, the Pediatric Institute, Kuala Lumpur General Hospital, Kuala Lumpur, Malaysia

CITATION:
Leung AKC, Barankin B, Lam JM, Leong KF. An atlas of lumps and bumps, part 43: blue nevi. Consultant. 2024;64(9):eXX.DOI:10.25270/con.2024.10.000004

CORRESPONDENCE:
Alexander K. C. Leung, MD, #200, 233 16th Ave NW, Calgary, AB T2M 0H5, Canada (aleung@ucalgary.ca)

EDITOR’S NOTE:
This article is part of a series describing and differentiating dermatologic lumps and bumps. To access previously published articles in the series, visit: https://www.consultant360.com/resource-center/atlas-lumps-and-bumps.