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Skin - Nonmelanocytic tumors

Benign nonmelanotic epidermal tumors / tumor-like lesions

Melanoacanthoma

Reviewer: Christopher Hale, M.D. (see Reviewers page)
Revised: 25 June 2012, last major update June 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● May be a pigmented variant of seborrheic keratosis
● Benign; cutaneous and oral variants, also called “melanoepithelioma”

Case reports
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● 65 year old man with “giant variant” melanoacanthoma (Indian J Dermatol 2011;56:79)

Clinical images
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Resembles melanoma

Gross description
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● Pigmented plaque, papule or nodule
● Dull surface

Micro description
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● Resembles seborrheic keratosis but with prominent, dendritic melanocytes with abundant melanin granules
● Melanocytes are scattered throughout the lesion
● No atypia

Micro images
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Basaloid cells form well-defined islands; numerous melanocytes are scattered throughout the lesion

Electron macroscopy description
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● Composed of benign keratinocytes and dendritic melanocytes, incomplete transfer of pigment from melanocytes to keratinocytes, normal population of Langerhan’s cells (J of Cutan Pathol 1978;5:127)

Differential diagnosis
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● Melanoma
● Pigmented malignant hidroacanthoma
● Pigmented squamous cell carcinoma
● Pigmented basal cell carcinoma

End of Skin - Nonmelanocytic tumors > Benign nonmelanotic epidermal tumors / tumor-like lesions > Melanoacanthoma

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