blue nevus

WKP

PO

Definition: Blue nevus is gray blue, and usually involves the scalp, sacrum or foot. It is a deep dermal lesion with abundant pigmentation.

Images

 https://twitter.com/Patholwalker/status/1496753718716510210

 Amelanotic blue naevus mimics dermatofibroma (DF). Usually focal pigment on close inspection. Melan A.

• https://twitter.com/BenjaminAwood/status/816098252076380160

 Agminated blue nevi

• https://twitter.com/JAADjournals/status/846069340231360513

Digital cases

 HPC:130
 pathxchange #2206
 UI:336 - Cellular Blue Nevus.
 JRC:10760 : Blue nevus.
 JRC:10784 : Blue nevus.
 JRC:10785 : Blue nevus.

Synopsis

 common blue nevus

• vaguely nodular collection of poorly melanized spindled melanocytes
• deeply pigmented dendritic melanocytes within thickened collagen bundles
• scattered melanophages
• no mitoses

 cellular blue nevus

• well-demarcated nodule
• fascicles and nests of tightly packed
• moderately sized, spindled to oval melanocytes with scattered melanophages
• centered in the reticular dermis
• blunt-ended, bulbus extensions that extend into the subcutaneous fat
• occasional mitoses
• significant cytologic atypia
• areas of necrosis absent

 epithelioid blue nevus (+/- with Carney complex)
 atypical blue nevus
 deep penetrating blue nevus
 sclerosing blue nevus
 amelanotic blue nevus
 malignant blue nevus: malignant melanoma arising in association with a cellular blue nevus or growing in a histologic pattern similar to that of a cellular blue nevus

• pronounced cytologic atypia
• hyperchromasia
• necrosis
• increased mitotic rate
• infiltrative growth pattern

Types

 classic blue nevus
 cellular blue nevus
 malignant blue nevus

Variants

 epithelioid blue nevus
 multiple blue nevi
 plaque-type blue nevus (16205067)
 amelanotic blue nevus

Localization

 skin
 Rarely: vagina, spermatic cord, uterine cervix, lymph node, prostate, oral mucosa, bronchus

Epidemiology

 most frequently noted in Asian populations (3-5% in adults)
 1-2% of white adults
 rarely found in blacks
 uncommon at birth or in the first few years of life, with an estimated prevalence of less than 1 case per 1000 population.

Differential diagnosis

 congenital dermal melanocytosis / “Mongolian spot”
 benign fibrous histiocytoma: hemosiderin pigment, no melanin
 dermatofibrosarcoma protuberans: more cellular, tight storiform pattern, infiltrative, has pigmented variant
 metastatic melanoma: “blue nevus-like cutaneous melanoma metastasis" can be differentiated by FISH probes
 malignant blue nevus, atypical blue nevus
 nevus of Ito / nevus of Ota

See also

 melanocytic lesions

• melanoyctic tumors