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blue nevus (dermal melanocytoma)
Variant of dermal nevus. An acquire firm, dark-blue to gray-black, nevus representing a local proliferation of dermal melanocytes.
Etiology:
- ectopic accumulation of melanin-producing melanocytes in the dermis during migration from neural crest sites to the skin
Epidemiology:
1) onset in late adolescence
2) equal sex distribution
Pathology:
1) melanin-containing fibroblast-like dermal melanocytes grouped in irregular bundles admixed with melanin-containing macrophages
2) excessive fibrous tissue production in upper reticular dermis
3) epidermis is normal
Clinical manifestations:
1) generally asymptomatic, of cosmetic concern
2) appearance is gradual
3) papules to nodules, generally < 1 cm in diameter
4) color: blue, blue-gray, blue-black, occasionally with target-like pattern of pigmentation
5) shape: generally round to oval
6) firm to palpation
7) most common on dorsal surface of hands or feet, but may occur at any site
Laboratory:
- biopsy to rule out melanoma
Differential diagnosis:
1) dermatofibroma
2) glomus tumor
3) primary nodular or metastatic melanoma
4) pigmented spindle cell (Spitz) nevus
5) traumatic tattoo
6) venous lakes (ectasias)
7) cavernous hemangiomas
9) Maffuci's syndrome
10) blue rubber bleb syndrome
Management:
1) most nevi remain unchanges
2) melanoma rarely arises from blue nevi
3) indications for surgical excision & dermatopathology
a) lesions > 1 cm
b) sudden appearance of lesion
c) change in lesion
General
dermal melanocytic nevus (basal cell nevus)
Database Correlations
OMIM 603670
References
- Saunders Manual of Medical Practice, Rakel (ed), WB Saunders,
Philadelphia, 1996, pg 960-61
- Color Atlas & Synopsis of Clinical Dermatology, Common
& Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY,
1997, pg 140