Blue nevusD22.-

Benign, early childhood acquired (less commonly congenital), atavistic, dermal, melanocytic neoplasm composed of mature, pigmented, dendritic, spindle cell and/or epithelioid melanocytes.

Acquired blue nevi may also occur in late adulthood and are often clinically mistaken for malignant melanoma because of their color.

• Simple blue nevus (most common type)
• Combined blue nevus ( Combined Naevus)
• Cellular (cell-rich) blue nevus
• Blue neuronaevus (Masson)
• Blue naevus, malignant.

The prevalence of blue nevus is about 1%.

• Mostly acquired in early childhood or early adulthood.
• More common in patients with dark skin type.
• Women are preferentially affected.

• Ubiquitous distribution possible.
• Extremities: Back of hands and feet (50% of all blue nevi are localized here)
• Face, Capillitium
• rarely mucous membranes.

Blue nevi have also been described in lymph nodes (capsule and trabecula) in the sense of pseudometastases and in the vagina, cervix and prostate.

The blue neuronaevus (Masson) is usually located on the buttocks.

Usually solitary, rarely > 1.0 cm in size, sharply defined, usually surprisingly coarse, indolent, blue-black nodule with smooth, shiny, like polished surface. Often, single hairs of the termial hairs penetrate the tumour. In other places, gaping follicle openings are visible on the surface.

As rare special forms are cocard-like nevi (target blue nevi), plaque-like blue nevi, grouped blue nevi ("agminate type"), eruptive multiple blue nevi (see also LAMB syndrome) and the combination with a melanocytic nevus (" combined nevus").

• Simple (vulgar) type (most common type): Proliferation of dendritic or bipolar spindle, pigment-rich melanocytes, which are partly grouped in single formations, partly also in wavy fascicles parallel to the surface, located in the dermis and partly also in subcutaneous fatty tissue. Typical is a pronounced fibrosis with sclerotic collagen fibres (clinical correlate is the very firm consistency). Mostly also numerous melanophages. The papillary dermis is usually left out.
• Combined type: Combination of a melanocytic nevus of dermal or compound type with a blue nevus. See also Combined nevus.
• Cellular type: Numerous, spindle or dendritic cells; in addition, cytoplasmic-rich, pigment-poor or -less, large oval cells with small spindle chromatin-tight nuclei. Often melanophages.
• Blue neuronaevus (Masson): Is a variant of the cell-rich blue nevus. Histologically nodular tumor proliferates in dermis and subcutis consisting of large melanocytes with oval nuclei and dendritic cells in the surrounding area.

The blue colour of the "blue nevus" is caused by the deep dermal black pigment and the Tyndall effect (milk glass effect) of the overlying uncoloured dermis and epidermis.

1. Cabral ES et al (2013) Acquired blue nevi in older individuals: retrospective case series from a Veterans Affairs population, 1991 to 2013 JAMA Dermatol 150:873-876
2. Gartmann H (1987) Target Blue Nevi. Arch Dermatol 123: 18
3. Hofmann U et al (1992) Grouped and combined blue nevi. dermatologist 43: 517-519
4. Pfaltz M et al (1989) Course and ultrastructure of the plaque-like nevus bleu. dermatologist 40: 355-357
5. Pinto A et al (2003) Epithelioid blue nevus of the oral mucosa: a rare histologic variant. Oral Surg Oral Med Oral Med Oral Pathol Oral Radiol Endod 96: 429-436
6. Tièche M (1906) About benign melanomas ("chromatophoromas") of the skin - "blue neavi. Virch Arch pathol Anat Physiol klin Med 186: 212-229
7. Zembowicz A et al (2011)Blue nevi and variants: an update. Arch Catholic Lab Med 135:327-336