Malignant Cellular Blue Nevus (Melanoma Arising in Cellular Blue Nevus)

 Symmetric and well circumscribed


image Often shows dumbbell-like appearance at low power

image Cells lack prominent cytologic atypia, mitotic activity, and necrosis


• Atypical cellular blue nevus
image Shows overlapping features with cellular blue nevus, but with increased cytologic atypia

image May have some mitoses, but not numerous or atypical

• Metastatic melanoma
image Usually mostly epithelioid-appearing melanocytes, fewer spindled cells, and no dendritic cells

image No associated benign blue nevus component



image
Malignant Cellular Blue Nevus With Necrosis
This was a very large and deep cellular lesion in an older adult patient. Note the central focus of necrosis image surrounded by cellular nodules of hyperchromatic-appearing cells.


image
Densely Cellular Fascicles of Spindle Cells in Malignant Cellular Blue Nevus
This malignant blue nevus shows densely cellular areas of atypical spindled melanocytes forming fascicular (sarcoma-like) arrangements.

image
High Magnification of Heavily Pigmented Malignant Cellular Blue Nevus
High magnification of a heavily pigmented malignant cellular blue nevus (MCBN) demonstrates significant nuclear atypia with prominent nucleoli image and a mitotic figure image in this case.

image
Ki-67 Immunostaining in Malignant Cellular Blue Nevus
Ki-67 immunostaining shows increased nuclear positivity in this malignant cellular blue nevus, with scattered enlarged, atypical-appearing nuclei staining image.


TERMINOLOGY


Abbreviations




• Malignant cellular blue nevus (MCBN)


Synonyms




• Melanoma arising in cellular blue nevus

• Melanoma mimicking cellular blue nevus


Definitions




• Malignant dermal-based melanocytic neoplasm with associated cellular blue nevus or features simulating cellular blue nevus


ETIOLOGY/PATHOGENESIS


Environmental Exposure




• May be related to solar damage


Genetics




• Multiple chromosomal abnormalities reported in some cases
image Gains and losses of entire chromosomal arms are most common aberrations

• Mutations in GNAQ and GNA11 have been reported

• Loss of nuclear BAP1 expression also recently identified

• 1 case reported to show mutation in hOGG-1 DNA repair enzyme


CLINICAL ISSUES


Epidemiology




• Incidence
image Very rare tumor

• Age
image Usually occurs in adults

• Sex
image More common in males


Presentation




• Dermal mass/nodular lesion
image May appear blue, bluish-gray, or bluish-black


Treatment




• Surgical approaches
image Complete and wider surgical excision is necessary for local removal

image Sentinel lymph node biopsy may be used for staging purposes but is of doubtful therapeutic utility


Prognosis




• Controversial
image Originally thought to be very aggressive, but recent reports may indicate lower malignant potential

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Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Malignant Cellular Blue Nevus (Melanoma Arising in Cellular Blue Nevus)

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